Annual Report

April 30, 2021

MFS^®  Corporate Bond Fund

MFB-ANN

MFS^® Corporate Bond Fund

CONTENTS

Letter from the CEO	1
Portfolio composition	2
Management review	4
Performance summary	6
Expense table	9
Portfolio of investments	11
Statement of assets and liabilities	26
Statement of operations	28
Statements of changes in net assets	29
Financial highlights	30
Notes to financial statements	39
Report of independent registered public accounting firm	51
Trustees and officers	53
Statement regarding liquidity risk management program	58
Proxy voting policies and information	59
Quarterly portfolio disclosure	59
Further information	59
Information about fund contracts and legal claims	59
Federal tax information	59
MFS® privacy notice	60

    

Contact information

back cover

The report is prepared for the general information of shareholders. It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED  •  MAY LOSE VALUE  •  NO BANK GUARANTEE

LETTER FROM THE CEO

Dear Shareholders:

Markets have experienced dramatic swings since the coronavirus pandemic brought the global economy to a standstill for several months early in 2020. While the speedy development of vaccines brightened the economic and market outlook, uncertainty remains as new variants of the virus appear and questions persist over how fast vaccines can be made widely available in the developing world.

Global central banks have taken aggressive steps to cushion the economic and market fallout related to the virus, and governments are deploying unprecedented levels of fiscal support. Having passed a $1.9 trillion stimulus package in March, the U.S. Congress is expected to approve additional stimulus later this year, some of it focused on infrastructure. Along with extraordinary government expenditures, pent-up consumer demand has fueled a surge in economic activity as coronavirus restrictions have been eased. Because of this, inflation pressures are being felt, and markets have pushed up yields on global government bonds, resulting in ripple effects across many financial markets.

A spirited debate is underway among investors over whether the current price pressures will persist or prove to be temporary, the consequence of pandemic-induced bottlenecks. The policy measures put in place to counteract the pandemic's effects have helped build a supportive environment and are encouraging economic recovery; however, if markets disconnect from fundamentals, they can sow the seeds of instability. As such, recent dramatic increases in speculative trading in cryptocurrencies, special-purpose acquisition companies (SPACs), and the like, bear watching.

In the aftermath of the crisis, we could see societal changes as households, businesses, and governments adjust to a new reality, and any such alterations could affect the investment landscape. For investors, events such as the COVID-19 outbreak demonstrate the importance of having a deep understanding of company fundamentals, and we have built our global research platform to do just that.

At MFS^®, we put our clients’ assets to work responsibly by carefully navigating the increasing complexity of global markets and economies. Guided by our long-term philosophy and adhering to our commitment to sustainable investing, we tune out the noise and aim to uncover what we believe are the best, most durable investment opportunities in the market. Our unique global investment platform combines collective expertise, long-term discipline, and thoughtful risk management to create sustainable value for investors.

Respectfully,

Michael W. Roberge

Chief Executive Officer

MFS Investment Management

June 15, 2021

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

1

Portfolio Composition

2

Portfolio Composition - continued

(d)	Duration is a measure of how much a bond’s price is likely to fluctuate with general changes in interest rates, e.g., if rates rise 1.00%, a bond with a 5-year duration is likely to lose about 5.00% of its value due to the interest rate move.

(i)

For purposes of this presentation, the components include the value of securities, and reflect the impact of the equivalent exposure of derivative positions, if any. These amounts may be negative from time to time. Equivalent exposure is a calculated amount that translates the derivative position into a reasonable approximation of the amount of the underlying asset that the portfolio would have to hold at a given point in time to have the same price sensitivity that results from the portfolio’s ownership of the derivative contract. When dealing with derivatives, equivalent exposure is a more representative measure of the potential impact of a position on portfolio performance than value. The bond component will include any accrued interest amounts.

(m)

In determining each instrument’s effective maturity for purposes of calculating the fund’s dollar-weighted average effective maturity, MFS uses the instrument’s stated maturity or, if applicable, an earlier date on which MFS believes it is probable that a maturity-shortening device (such as a put, pre-refunding or prepayment) will cause the instrument to be repaid. Such an earlier date can be substantially shorter than the instrument’s stated maturity.

(o)	Less than 0.1%.

Where the fund holds convertible bonds, they are treated as part of the equity portion of the portfolio.

Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. Please see the Statement of Assets and Liabilities for additional information related to the fund’s cash position and other assets and liabilities.

Other includes equivalent exposure from currency derivatives and/or any offsets to derivative positions.

Percentages are based on net assets as of April 30, 2021.

The portfolio is actively managed and current holdings may be different.

3

Management Review

Summary of Results

For the twelve months ended April 30, 2021, Class A shares of the MFS Corporate Bond Fund (fund) provided a total return of 4.94%, at net asset value. This compares with a return of 4.25% for the fund’s benchmark, the Bloomberg Barclays U.S. Credit Bond Index.

Market Environment

After experiencing an abrupt decline in response to the initial wave of the coronavirus pandemic, markets staged a sharp rally that took global equities to record highs near the end of the period. Central banks and fiscal authorities undertook astonishing levels of stimulus to offset the economic effects of government-imposed social-distancing measures meant to slow the spread of the virus. At this point, the global economy looks to have experienced the shortest — albeit the deepest — recession in the postwar period. However, its recovery remains subject to a number of uncertainties as the rollout of coronavirus vaccines remains highly variable in different countries. Even the distribution of vaccines in developed economies has been sluggish due to supply constraints and concerns over potential side effects. In some jurisdictions, there remain worries over whether enough people will get vaccinated to bring about herd immunity.

Around the world, central banks responded quickly and massively to the crisis with programs to improve liquidity and support markets. These undertakings proved largely successful in helping to restore market function, ease volatility and stimulate a prolonged rebound. In the middle of the period, the US Federal Reserve adopted a new, flexible, average-inflation-targeting framework, which is expected to result in the federal funds rate remaining at low levels longer than under its previous model. Due to relatively manageable external liabilities and balances of payments in many countries and persistently low inflation, even emerging market countries were able to implement countercyclical policies — a departure from the usual market-dictated response to risk-off crises.

Late in the period, we saw the threat of resurgent inflation resulting from monumental levels of economic stimulus and the unleashing of pandemic-induced pent-up demand. Meanwhile, raw materials prices rebounded strongly on account of the surprising resilience of the global manufacturing sector during the pandemic. In response to these factors, global government bond yields have risen materially in recent months and market leadership has shifted from a handful of mega-cap technology companies to a broader array of small-cap and value stocks. At the same time, signs of excess investor enthusiasm have been seen in pockets of the market, such as stocks that are popular with the users of online message boards and equities issued by special purpose acquisition companies (SPACs).

Factors Affecting Performance

Relative to the Bloomberg Barclays U.S. Credit Bond Index, the fund’s overweight allocation to the “BBB” rated^(r) credit quality segment, and its underweight position in both “AAA” and “A” rated bonds, contributed to relative performance. Favorable

4

Management Review - continued

security selection within the consumer cyclical sector also helped in relative terms. Additionally, the fund's positioning along the yield curve^(y) and shorter duration^(d) stance supported relative returns as interest rates generally rose throughout the reporting period.

Conversely, the combination of the fund's overweight position and security selection in the electric sector, and its underweight positions in both the energy and sovereign sectors, held back relative returns. Bond selection in the capital goods sector also weakened relative performance. The fund’s cash and/or cash equivalents position during the period was another detractor from relative performance.

Respectfully,

Portfolio Manager(s)

Alexander Mackey, Henry Peabody, and Robert Persons

Note to Shareholders: Effective June 30, 2021, Robert Persons is no longer a Portfolio Manager of the fund.

(d)	Duration is a measure of how much a bond’s price is likely to fluctuate with general changes in interest rates, e.g., if rates rise 1.00%, a bond with a 5-year duration is likely to lose about 5.00% of its value.

(r)

Bonds rated “BBB”, “Baa”, or higher are considered investment grade; bonds rated “BB”, “Ba”, or below are considered non-investment grade. The source for bond quality ratings is Moody's Investors Service, Standard & Poor's, and Fitch, Inc. and are applied using the following hierarchy: If all three agencies provide a rating, the middle rating (after dropping the highest and lowest ratings) is assigned; if two of the three agencies rate a security, the lower of the two is assigned. If none of the 3 Rating Agencies above assign a rating, but the security is rated by DBRS Morningstar, then the DBRS Morningstar rating is assigned. Ratings are shown in the S&P and Fitch scale (e.g., AAA). For securities that are not rated by any of the rating agencies, the security is considered Not Rated.

(y)	A yield curve graphically depicts the yields of different maturity bonds of the same credit quality and type; a normal yield curve is upward sloping, with short-term rates lower than long-term rates.

The views expressed in this report are those of the portfolio manager(s) only through the end of the period of the report as stated on the cover and do not necessarily reflect the views of MFS or any other person in the MFS organization. These views are subject to change at any time based on market or other conditions, and MFS disclaims any responsibility to update such views. These views may not be relied upon as investment advice or an indication of trading intent on behalf of any MFS portfolio. References to specific securities are not recommendations of such securities, and may not be representative of any MFS portfolio’s current or future investments.

5

Performance Summary THROUGH 4/30/21

The following chart illustrates a representative class of the fund’s historical performance in comparison to its benchmark(s). Performance results include the deduction of the maximum applicable sales charge and reflect the percentage change in net asset value, including reinvestment of dividends and capital gains distributions. The performance of other share classes will be greater than or less than that of the class depicted below. Benchmarks are unmanaged and may not be invested in directly. Benchmark returns do not reflect sales charges, commissions or expenses. (See Notes to Performance Summary.)

Performance data shown represents past performance and is no guarantee of future results. Investment return and principal value fluctuate so your shares, when sold, may be worth more or less than the original cost; current performance may be lower or higher than quoted. The performance shown does not reflect the deduction of taxes, if any, that a shareholder would pay on fund distributions or the redemption of fund shares.

Growth of a Hypothetical $10,000 Investment

6

Performance Summary  - continued

Total Returns through 4/30/21

Average annual without sales charge

Share Class	Class Inception Date	1-yr	5-yr	10-yr	Life (t)
A	5/08/74	4.94%	4.78%	4.68%	N/A
B	9/07/93	4.17%	4.00%	3.91%	N/A
C	1/03/94	4.10%	4.00%	3.91%	N/A
I	1/02/97	5.14%	5.02%	4.92%	N/A
R1	4/01/05	4.10%	4.00%	3.91%	N/A
R2	10/31/03	4.68%	4.52%	4.42%	N/A
R3	4/01/05	4.94%	4.78%	4.68%	N/A
R4	4/01/05	5.13%	5.04%	4.94%	N/A
R6	6/01/12	5.23%	5.13%	N/A	4.81%

Comparative benchmark(s)

Bloomberg Barclays U.S. Credit Bond Index (f)	4.25%	4.63%	4.77%	N/A

Average annual with sales charge

A With Initial Sales Charge (4.25%)	0.48%	3.87%	4.22%	N/A
B With CDSC (Declining over six years from 4% to 0%) (v)	0.17%	3.66%	3.91%	N/A
C With CDSC (1% for 12 months) (v)	3.10%	4.00%	3.91%	N/A

CDSC – Contingent Deferred Sales Charge.

Class I, R1, R2, R3, R4, and R6 shares do not have a sales charge.

(f)	Source: FactSet Research Systems Inc.
(t)	For the period from the class inception date through the stated period end (for those share classes with less than 10 years of performance history). No comparative benchmark performance information is provided for “life” periods. (See Notes to Performance Summary.)
(v)	Assuming redemption at the end of the applicable period.

Benchmark Definition(s)

Bloomberg Barclays U.S. Credit Bond Index^(a) - a market capitalization-weighted index that measures the performance of publicly issued, SEC-registered, U.S. corporate and specified foreign debentures and secured notes that meet specified maturity, liquidity, and quality requirements.

It is not possible to invest directly in an index.

(a)

BLOOMBERG ® is a trademark and service mark of Bloomberg Finance L.P. and its affiliates (collectively “Bloomberg”). BARCLAYS® is a trademark and service mark of Barclays Bank Plc (collectively with its affiliates, “Barclays”), used under license. Bloomberg or Bloomberg's licensors, including Barclays, own all proprietary rights in the Bloomberg Barclays Indices. Neither Bloomberg nor Barclays approves or endorses this material, or guarantees the

7

Performance Summary  - continued

accuracy or completeness of any information herein, or makes any warranty, express or implied, as to the results to be obtained therefrom, and, to the maximum extent allowed by law, neither shall have any liability or responsibility for injury or damages arising in connection therewith.

Notes to Performance Summary

Average annual total return represents the average annual change in value for each share class for the periods presented. Life returns are presented where the share class has less than 10 years of performance history and represent the average annual total return from the class inception date to the stated period end date. As the fund's share classes may have different inception dates, the life returns may represent different time periods and may not be comparable. As a result, no comparative benchmark performance information is provided for life periods.

Performance results reflect any applicable expense subsidies and waivers in effect during the periods shown. Without such subsidies and waivers the fund's performance results would be less favorable. Please see the prospectus and financial statements for complete details.

Performance results do not include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles and may differ from amounts reported in the financial highlights.

From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

8

Expense Table

Fund expenses borne by the shareholders during the period,
November 1, 2020 through April 30, 2021

As a shareholder of the fund, you incur two types of costs: (1) transaction costs, including sales charges (loads) on certain purchase or redemption payments, and (2) ongoing costs, including management fees; distribution and service (12b-1) fees; and other fund expenses. This example is intended to help you understand your ongoing costs (in dollars) of investing in the fund and to compare these costs with the ongoing costs of investing in other mutual funds.

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period November 1, 2020 through April 30, 2021.

Actual Expenses

The first line for each share class in the following table provides information about actual account values and actual expenses. You may use the information in this line, together with the amount you invested, to estimate the expenses that you paid over the period. Simply divide your account value by $1,000 (for example, an $8,600 account value divided by $1,000 = 8.6), then multiply the result by the number in the first line under the heading entitled “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes

The second line for each share class in the following table provides information about hypothetical account values and hypothetical expenses based on the fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the fund’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transactional costs, such as sales charges (loads). Therefore, the second line for each share class in the table is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds. In addition, if these transactional costs were included, your costs would have been higher.

9

Expense Table - continued

Share Class		Annualized Expense Ratio	Beginning Account Value 11/01/20	Ending Account Value 4/30/21	Expenses Paid During Period (p) 11/01/20-4/30/21
A	Actual	0.76%	$1,000.00	$993.76	$3.76
	Hypothetical (h)	0.76%	$1,000.00	$1,021.03	$3.81
B	Actual	1.51%	$1,000.00	$990.64	$7.45
	Hypothetical (h)	1.51%	$1,000.00	$1,017.31	$7.55
C	Actual	1.51%	$1,000.00	$989.97	$7.45
	Hypothetical (h)	1.51%	$1,000.00	$1,017.31	$7.55
I	Actual	0.51%	$1,000.00	$994.98	$2.52
	Hypothetical (h)	0.51%	$1,000.00	$1,022.27	$2.56
R1	Actual	1.51%	$1,000.00	$989.98	$7.45
	Hypothetical (h)	1.51%	$1,000.00	$1,017.31	$7.55
R2	Actual	1.01%	$1,000.00	$992.51	$4.99
	Hypothetical (h)	1.01%	$1,000.00	$1,019.79	$5.06
R3	Actual	0.76%	$1,000.00	$993.77	$3.76
	Hypothetical (h)	0.76%	$1,000.00	$1,021.03	$3.81
R4	Actual	0.51%	$1,000.00	$995.01	$2.52
	Hypothetical (h)	0.51%	$1,000.00	$1,022.27	$2.56
R6	Actual	0.40%	$1,000.00	$995.49	$1.98
	Hypothetical (h)	0.40%	$1,000.00	$1,022.81	$2.01

(h)	5% class return per year before expenses.

(p)

“Expenses Paid During Period” are equal to each class’s annualized expense ratio, as shown above, multiplied by the average account value over the period, multiplied by 181/365 (to reflect the one-half year period). Expenses paid do not include any applicable sales charges (loads). If these transaction costs had been included, your costs would have been higher.

10

Portfolio of Investments

4/30/21

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.

Issuer			Shares/Par	Value ($)
Bonds – 94.2%
Aerospace & Defense – 2.5%
BAE Systems PLC, 3.4%, 4/15/2030 (n)		$	17,185,000	$    18,355,825
Boeing Co., 5.15%, 5/01/2030			9,602,000	11,167,737
Huntington Ingalls Industries, Inc., 3.483%, 12/01/2027			11,950,000	12,999,848
Huntington Ingalls Industries, Inc., 4.2%, 5/01/2030			8,584,000	9,651,595
L3Harris Technologies, Inc., 3.85%, 6/15/2023			12,356,000	13,162,183
L3Harris Technologies, Inc., 2.9%, 12/15/2029			13,420,000	13,981,857
Northrop Grumman Corp., 2.93%, 1/15/2025			23,041,000	24,664,271
Raytheon Technologies Corp., 4.125%, 11/16/2028			9,190,000	10,432,757
TransDigm, Inc., 6.25%, 3/15/2026 (n)			20,921,000	22,150,109
TransDigm, Inc., 4.625%, 1/15/2029 (n)			17,645,000	17,389,324
				$153,955,506
Apparel Manufacturers – 0.1%
Tapestry, Inc., 4.125%, 7/15/2027		$	6,054,000	$     6,631,903
Asset-Backed & Securitized – 0.0%
Bayview Financial Revolving Mortgage Loan Trust, FLR, 1.711% (LIBOR - 1mo. + 1.6%), 12/28/2040 (n)		$	537,202	$       573,186
JPMorgan Chase Commercial Mortgage Securities Corp., 5.788%, 7/15/2042 (n)			694,029	571,603
Lehman Brothers Commercial Conduit Mortgage Trust, 1.102%, 2/18/2030 (i)			94,879	2
				$1,144,791
Automotive – 2.8%
Daimler Finance North America LLC, 1.45%, 3/02/2026 (n)		$	16,672,000	$    16,722,736
General Motors Co., 6.8%, 10/01/2027			8,000,000	10,058,404
Hyundai Capital America, 3.5%, 11/02/2026 (n)			1,571,000	1,692,094
Hyundai Capital America, 3%, 2/10/2027 (n)			28,430,000	29,806,836
Hyundai Capital America, 1.8%, 1/10/2028 (n)			18,721,000	18,168,297
Hyundai Capital America, 6.375%, 4/08/2030 (n)			8,601,000	10,950,007
Lear Corp., 3.8%, 9/15/2027			36,241,000	39,848,911
Lear Corp., 5.25%, 5/15/2049			6,808,000	8,031,368
Toyota Motor Credit Corp., 3.375%, 4/01/2030			20,667,000	22,717,422
Volkswagen Group of America Finance LLC, 3.35%, 5/13/2025 (n)			14,915,000	16,143,971
				$174,140,046

11

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Broadcasting – 2.4%
Discovery Communications LLC, 4%, 9/15/2055 (n)		$	8,715,000	$     8,522,151
Discovery, Inc., 4.125%, 5/15/2029			7,075,000	7,805,672
Discovery, Inc., 5.3%, 5/15/2049			9,152,000	10,954,932
Fox Corp., 5.476%, 1/25/2039			13,338,000	16,724,845
Netflix, Inc., 4.875%, 6/15/2030 (n)			18,479,000	21,435,640
Prosus N.V., 3.832%, 2/08/2051 (n)			15,426,000	14,090,542
RELX Capital, Inc., 3%, 5/22/2030			10,495,000	10,975,750
Walt Disney Co., 3.5%, 5/13/2040			33,771,000	36,088,902
Walt Disney Co., 3.6%, 1/13/2051			16,836,000	18,122,070
				$144,720,504
Brokerage & Asset Managers – 1.1%
Intercontinental Exchange, Inc., 2.1%, 6/15/2030		$	46,198,000	$    45,190,421
Intercontinental Exchange, Inc., 1.85%, 9/15/2032			10,946,000	10,111,072
Intercontinental Exchange, Inc., 3%, 9/15/2060			11,809,000	10,590,276
				$65,891,769
Building – 1.5%
CRH America Finance, Inc., 4.5%, 4/04/2048 (n)		$	16,362,000	$    19,354,326
Martin Marietta Materials, Inc., 4.25%, 7/02/2024			7,431,000	8,157,682
Martin Marietta Materials, Inc., 3.45%, 6/01/2027			8,095,000	8,872,202
Martin Marietta Materials, Inc., 3.5%, 12/15/2027			14,186,000	15,717,834
Masco Corp., 4.5%, 5/15/2047			12,265,000	14,319,331
Vulcan Materials Co., 4.5%, 6/15/2047			19,500,000	22,735,680
				$89,157,055
Business Services – 3.6%
Equinix, Inc., 2.625%, 11/18/2024		$	17,822,000	$    18,783,121
Equinix, Inc., 5.375%, 5/15/2027			4,197,000	4,509,593
Equinix, Inc., 3%, 7/15/2050			25,475,000	23,345,797
Fiserv, Inc., 2.25%, 6/01/2027			20,183,000	20,847,271
Fiserv, Inc., 4.4%, 7/01/2049			13,643,000	15,910,087
Global Payments, Inc., 2.9%, 5/15/2030			23,779,000	24,391,247
Iron Mountain, Inc., 4.5%, 2/15/2031 (n)			30,417,000	30,334,266
MSCI, Inc., 4%, 11/15/2029 (n)			11,808,000	12,339,360
MSCI, Inc., 3.625%, 9/01/2030 (n)			2,669,000	2,711,517
MSCI, Inc., 3.875%, 2/15/2031 (n)			20,299,000	20,801,806
NXP B.V./NXP Funding LLC, 3.15%, 5/01/2027 (n)			9,345,000	10,015,381
Visa, Inc., 4.15%, 12/14/2035			12,578,000	15,084,914
Visa, Inc., 3.65%, 9/15/2047			9,718,000	10,901,928
Western Union Co., 2.85%, 1/10/2025			10,521,000	11,109,766
				$221,086,054

12

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Cable TV – 3.1%
CCO Holdings LLC/CCO Holdings Capital Corp., 4.5%, 8/15/2030 (n)		$	8,557,000	$     8,705,806
CCO Holdings LLC/CCO Holdings Capital Corp., 4.5%, 5/01/2032 (n)			8,551,000	8,636,510
Charter Communications Operating LLC/Charter Communications Operating Capital Corp., 6.384%, 10/23/2035			11,627,000	15,160,607
Charter Communications Operating LLC/Charter Communications Operating Capital Corp., 5.375%, 5/01/2047			31,409,000	36,855,169
Comcast Corp., 1.95%, 1/15/2031			8,200,000	7,931,242
Comcast Corp., 4.6%, 10/15/2038			19,500,000	23,712,396
Cox Communications, Inc., 3.5%, 8/15/2027 (n)			11,693,000	12,737,445
Cox Communications, Inc., 4.6%, 8/15/2047 (n)			3,670,000	4,315,659
Sirius XM Holdings, Inc., 5.5%, 7/01/2029 (n)			8,869,000	9,584,063
Sirius XM Radio, Inc., 5.375%, 7/15/2026 (n)			19,940,000	20,592,038
Sirius XM Radio, Inc., 5%, 8/01/2027 (n)			9,137,000	9,568,242
Sirius XM Radio, Inc., 4.125%, 7/01/2030 (n)			22,359,000	22,359,000
Time Warner Cable, Inc., 4.5%, 9/15/2042			7,034,000	7,611,324
				$187,769,501
Chemicals – 0.7%
Alpek SAB de C.V., 3.25%, 2/25/2031 (n)		$	16,565,000	$    16,316,691
LYB International Finance III, LLC, 3.625%, 4/01/2051			12,741,000	12,738,946
Sherwin-Williams Co., 4.5%, 6/01/2047			11,884,000	14,160,514
				$43,216,151
Computer Software – 1.7%
Dell International LLC/EMC Corp., 4.9%, 10/01/2026 (n)		$	27,891,000	$    32,040,046
Microsoft Corp., 3.45%, 8/08/2036			9,522,000	10,615,694
Microsoft Corp., 2.525%, 6/01/2050			15,025,000	13,992,199
Microsoft Corp., 2.921%, 3/17/2052			18,953,000	18,939,457
VeriSign, Inc., 4.625%, 5/01/2023			7,628,000	7,650,884
VeriSign, Inc., 4.75%, 7/15/2027			17,901,000	19,061,701
				$102,299,981
Computer Software - Systems – 0.9%
Apple, Inc., 2.05%, 9/11/2026		$	31,675,000	$    33,091,265
Apple, Inc., 4.5%, 2/23/2036			10,000,000	12,388,512
Apple, Inc., 3.85%, 8/04/2046			8,346,000	9,582,032
				$55,061,809
Conglomerates – 1.2%
Carrier Global Corp., 3.377%, 4/05/2040		$	8,439,000	$     8,514,994
Roper Technologies, Inc., 4.2%, 9/15/2028			12,199,000	13,931,249
Roper Technologies, Inc., 2.95%, 9/15/2029			9,027,000	9,481,522

13

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Conglomerates – continued
Roper Technologies, Inc., 2%, 6/30/2030		$	11,092,000	$    10,684,502
Westinghouse Air Brake Technologies Corp., 4.4%, 3/15/2024			6,283,000	6,852,015
Westinghouse Air Brake Technologies Corp., 3.2%, 6/15/2025			5,611,000	5,985,254
Westinghouse Air Brake Technologies Corp., 4.95%, 9/15/2028			16,536,000	19,018,527
				$74,468,063
Consumer Products – 0.9%
Kimberly-Clark Corp., 3.1%, 3/26/2030		$	4,641,000	$     5,041,001
Mattel, Inc., 3.75%, 4/01/2029 (n)			31,712,000	32,499,092
Reckitt Benckiser Treasury Services PLC, 3%, 6/26/2027 (n)			16,079,000	17,332,605
				$54,872,698
Consumer Services – 2.5%
Amazon.com, Inc., 2.5%, 6/03/2050		$	21,768,000	$    19,564,806
Booking Holdings, Inc., 3.65%, 3/15/2025			6,166,000	6,741,554
Booking Holdings, Inc., 3.6%, 6/01/2026			18,768,000	20,820,038
Booking Holdings, Inc., 3.55%, 3/15/2028			14,807,000	16,183,687
Experian Finance PLC, 2.75%, 3/08/2030 (n)			21,848,000	22,389,780
IHS Markit Ltd., 3.625%, 5/01/2024			5,742,000	6,179,540
IHS Markit Ltd., 4.75%, 2/15/2025 (n)			9,259,000	10,396,931
IHS Markit Ltd., 4%, 3/01/2026 (n)			6,085,000	6,733,113
IHS Markit Ltd., 4.25%, 5/01/2029			8,611,000	9,746,705
MercadoLibre, Inc., 3.125%, 1/14/2031			21,974,000	21,018,131
Service Corp. International, 5.125%, 6/01/2029			13,081,000	14,122,117
				$153,896,402
Containers – 0.6%
Ball Corp., 5.25%, 7/01/2025		$	1,942,000	$     2,196,888
Ball Corp., 4.875%, 3/15/2026			11,631,000	13,026,720
Ball Corp., 2.875%, 8/15/2030			24,838,000	23,985,311
				$39,208,919
Electrical Equipment – 0.6%
Arrow Electronics, Inc., 3.25%, 9/08/2024		$	16,437,000	$    17,608,966
Arrow Electronics, Inc., 3.875%, 1/12/2028			17,987,000	19,856,725
				$37,465,691
Electronics – 2.7%
Broadcom Corp./Broadcom Cayman Finance Ltd., 3.875%, 1/15/2027		$	24,352,000	$    26,679,910
Broadcom Corp./Broadcom Cayman Finance Ltd., 3.5%, 1/15/2028			11,864,000	12,707,406
Broadcom, Inc., 4.3%, 11/15/2032			26,036,000	28,736,501
Broadcom, Inc., 3.469%, 4/15/2034 (n)			50,649,000	51,207,786

14

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Electronics – continued
Sensata Technologies, Inc., 4.375%, 2/15/2030 (n)		$	34,545,000	$    36,116,970
Sensata Technologies, Inc., 3.75%, 2/15/2031 (n)			10,126,000	10,055,523
				$165,504,096
Emerging Market Quasi-Sovereign – 0.4%
Ecopetrol S.A., 5.375%, 6/26/2026		$	8,381,000	$     9,405,158
Ecopetrol S.A., 6.875%, 4/29/2030			12,572,000	15,243,550
				$24,648,708
Emerging Market Sovereign – 0.9%
Republic of Panama, 2.252%, 9/29/2032		$	42,716,000	$    40,783,528
United Mexican States, 2.659%, 5/24/2031			16,125,000	15,507,251
				$56,290,779
Energy - Independent – 0.2%
Hess Corp., 5.8%, 4/01/2047		$	8,418,000	$    10,265,410
Energy - Integrated – 1.3%
Cenovus Energy, Inc., 5.375%, 7/15/2025		$	21,571,000	$    24,526,132
Eni S.p.A., 4.75%, 9/12/2028 (n)			14,052,000	16,249,077
Eni S.p.A., 4.25%, 5/09/2029 (n)			12,206,000	13,682,747
Total Capital International S.A., 3.127%, 5/29/2050			25,158,000	24,130,755
				$78,588,711
Entertainment – 0.3%
Royal Caribbean Cruises Ltd., 3.7%, 3/15/2028		$	22,622,000	$    21,485,697
Financial Institutions – 2.0%
AerCap Ireland Capital DAC, 4.875%, 1/16/2024		$	11,687,000	$    12,808,553
AerCap Ireland Capital DAC, 6.5%, 7/15/2025			3,261,000	3,838,012
AerCap Ireland Capital DAC, 3.65%, 7/21/2027			29,033,000	30,849,156
Avolon Holdings Funding Ltd., 5.5%, 1/15/2026 (n)			8,919,000	9,984,819
Avolon Holdings Funding Ltd., 2.125%, 2/21/2026 (n)			8,201,000	8,017,865
Avolon Holdings Funding Ltd., 4.25%, 4/15/2026 (n)			10,188,000	10,864,270
Avolon Holdings Funding Ltd., 4.375%, 5/01/2026 (n)			11,590,000	12,398,043
Avolon Holdings Funding Ltd., 3.25%, 2/15/2027 (n)			13,674,000	13,908,938
Avolon Holdings Funding Ltd., 2.75%, 2/21/2028 (n)			23,742,000	23,096,009
				$125,765,665
Food & Beverages – 5.1%
Anheuser-Busch InBev Worldwide, Inc., 3.5%, 6/01/2030		$	16,906,000	$    18,457,512
Anheuser-Busch InBev Worldwide, Inc., 4.375%, 4/15/2038			8,822,000	10,040,861
Anheuser-Busch InBev Worldwide, Inc., 5.55%, 1/23/2049			16,480,000	21,307,360
Anheuser-Busch InBev Worldwide, Inc., 4.75%, 4/15/2058			15,286,000	17,913,167
Aramark Services, Inc., 6.375%, 5/01/2025 (n)			14,977,000	15,931,784

15

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Food & Beverages – continued
Aramark Services, Inc., 5%, 2/01/2028 (n)		$	15,117,000	$    15,816,161
Campbell Soup Co., 2.375%, 4/24/2030			4,704,000	4,671,900
Campbell Soup Co., 3.125%, 4/24/2050			6,884,000	6,430,876
Constellation Brands, Inc., 4.25%, 5/01/2023			27,944,000	29,946,067
Constellation Brands, Inc., 2.875%, 5/01/2030			4,163,000	4,304,315
Constellation Brands, Inc., 3.75%, 5/01/2050			5,973,000	6,305,846
Danone S.A., 2.589%, 11/02/2023 (n)			23,885,000	24,939,935
Diageo Capital PLC, 2.375%, 10/24/2029			21,271,000	21,623,563
Diageo Capital PLC, 2%, 4/29/2030			21,083,000	20,706,116
JBS USA LLC/JBS USA Finance, Inc., 6.75%, 2/15/2028 (n)			17,787,000	19,652,856
JBS USA Lux S.A./JBS USA Finance, Inc., 6.5%, 4/15/2029 (n)			13,224,000	14,844,072
Keurig Dr Pepper, Inc., 3.2%, 5/01/2030			2,379,000	2,536,164
Keurig Dr Pepper, Inc., 3.8%, 5/01/2050			4,914,000	5,243,192
Mondelez International, Inc., 2.625%, 9/04/2050			30,758,000	26,918,487
PepsiCo, Inc., 3.5%, 3/19/2040			10,448,000	11,471,597
SYSCO Corp., 2.4%, 2/15/2030			4,205,000	4,200,371
SYSCO Corp., 4.45%, 3/15/2048			7,564,000	8,680,510
				$311,942,712
Gaming & Lodging – 2.3%
GLP Capital LP/GLP Financing II, Inc., 5.75%, 6/01/2028		$	24,600,000	$    28,639,653
GLP Capital LP/GLP Financing II, Inc., 5.3%, 1/15/2029			5,895,000	6,699,373
GLP Capital LP/GLP Financing II, Inc., 4%, 1/15/2031			4,167,000	4,394,351
Hilton Domestic Operating Co., Inc., 4.875%, 1/15/2030			17,700,000	18,872,979
Hilton Domestic Operating Co., Inc., 3.625%, 2/15/2032 (n)			16,374,000	16,102,519
Marriott International, Inc., 5.75%, 5/01/2025			2,086,000	2,401,285
Marriott International, Inc., 3.75%, 10/01/2025			8,873,000	9,558,927
Marriott International, Inc., 4%, 4/15/2028			33,912,000	36,544,171
Marriott International, Inc., 2.85%, 4/15/2031			9,324,000	9,268,578
Sands China Ltd., 3.8%, 1/08/2026			5,725,000	6,061,744
				$138,543,580
Insurance - Health – 0.5%
UnitedHealth Group, Inc., 4.625%, 7/15/2035		$	18,120,000	$    22,117,089
UnitedHealth Group, Inc., 3.5%, 8/15/2039			6,918,000	7,479,079
				$29,596,168
Insurance - Property & Casualty – 2.2%
Aon Corp., 3.75%, 5/02/2029		$	25,796,000	$    28,692,168
Berkshire Hathaway Finance Corp., 2.85%, 10/15/2050			18,308,000	17,348,798
Fairfax Financial Holdings Ltd., 4.625%, 4/29/2030			19,867,000	22,002,527
Hartford Financial Services Group, Inc., 3.6%, 8/19/2049			18,720,000	19,737,272
Liberty Mutual Group, Inc., 3.951%, 10/15/2050 (n)			5,333,000	5,595,024
Marsh & McLennan Cos., Inc., 3.5%, 6/03/2024			6,766,000	7,287,466

16

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Insurance - Property & Casualty – continued
Marsh & McLennan Cos., Inc., 4.75%, 3/15/2039		$	13,978,000	$    17,526,950
Marsh & McLennan Cos., Inc., 4.35%, 1/30/2047			6,467,000	7,749,246
Willis North America, Inc., 2.95%, 9/15/2029			10,826,000	11,331,079
				$137,270,530
Machinery & Tools – 0.6%
CNH Industrial Capital LLC, 4.2%, 1/15/2024		$	9,230,000	$    10,044,250
CNH Industrial Capital LLC, 1.875%, 1/15/2026			7,745,000	7,865,496
CNH Industrial Capital LLC, 3.85%, 11/15/2027			16,974,000	18,817,585
				$36,727,331
Major Banks – 13.3%
Australia and New Zealand Banking Group Ltd., 2.57%, 11/25/2035 (n)		$	23,146,000	$    22,009,994
Bank of America Corp., 3.124% to 1/20/2022, FLR (LIBOR - 3mo. + 1.16%) to 1/20/2023			17,201,000	17,542,995
Bank of America Corp., 3.004%, 12/20/2023			1,782,000	1,852,478
Bank of America Corp., 4.125%, 1/22/2024			14,866,000	16,273,628
Bank of America Corp., 4.45%, 3/03/2026			4,537,000	5,138,749
Bank of America Corp., 3.5%, 4/19/2026			19,080,000	21,051,022
Bank of America Corp., 4.183%, 11/25/2027			25,000,000	27,956,265
Bank of America Corp., 3.419% to 12/20/2027, FLR (LIBOR - 3mo. + 1.04%) to 12/20/2028			15,825,000	17,139,601
Bank of America Corp., 3.97% to 3/05/2028, FLR (LIBOR - 3mo. + 1.07%) to 3/05/2029			7,314,000	8,156,442
Bank of America Corp., 2.496% to 2/13/2030, FLR (LIBOR - 3mo. + 0.99%) to 2/13/2031			23,725,000	23,793,706
Bank of America Corp., 2.676% to 6/19/2040, FLR (SOFR + 1.93%) to 6/19/2041			35,373,000	33,232,833
Bank of America Corp., 3.311% to 4/22/2041, FLR (SOFR + 1.58%) to 4/22/2042			42,029,000	42,881,708
Commonwealth Bank of Australia, 3.61% to 9/12/2029, FLR (CMT - 1yr. + 2.05%) to 9/12/2034 (n)			12,534,000	13,049,462
Commonwealth Bank of Australia, 3.305%, 3/11/2041 (n)			24,424,000	24,023,162
Credit Agricole S.A., 1.247% to 1/26/2026, FLR (SOFR + 0.89162%) to 1/26/2027 (n)			12,447,000	12,223,445
Credit Suisse Group AG, 4.194% to 4/01/2030, FLR (SOFR + 3.73%), to 4/01/2031 (n)			19,521,000	21,585,401
Credit Suisse Group AG, 4.5% to 3/03/2031, FLR (CMT - 1yr. + 3.554%) to 6/09/2070 (n)			12,847,000	12,268,885
Goldman Sachs Group, Inc., 2.6%, 2/07/2030			30,654,000	31,299,033
HSBC Holdings PLC, 2.357% to 8/18/2030, FLR (SOFR + 1.947%) to 8/18/2031			42,077,000	41,004,925
HSBC Holdings PLC, 5.25%, 3/14/2044			11,033,000	13,677,852

17

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Major Banks – continued
JPMorgan Chase & Co., 3.2%, 6/15/2026		$	9,000,000	$     9,774,909
JPMorgan Chase & Co., 3.782% to 2/01/2027, FLR (LIBOR - 3mo. + 1.337%) to 2/01/2028			35,000,000	38,856,715
JPMorgan Chase & Co., 3.54%, 5/01/2028			18,887,000	20,669,178
JPMorgan Chase & Co., 3.964%, 11/15/2048			12,400,000	13,791,402
JPMorgan Chase & Co., 3.897% to 1/23/2048, FLR (LIBOR - 3mo. + 1.22%) to  1/23/2049			20,011,000	22,011,715
Morgan Stanley, 3.125%, 1/23/2023			22,096,000	23,132,523
Morgan Stanley, 0.864% to 10/21/2024, FLR (SOFR + 0.745%) to 10/21/2025			8,681,000	8,669,505
Morgan Stanley, 0.985% to 12/10/2025, FLR (SOFR + 0.72%) to 12/10/2026			39,037,000	38,311,548
Morgan Stanley, 4.431% to 1/23/2029, FLR (LIBOR - 3mo. + 1.63%) to 1/23/2030			8,224,000	9,483,057
Morgan Stanley, 2.699% to 1/22/2030, FLR (SOFR + 1.143%) to 1/22/2031			54,040,000	55,229,457
Morgan Stanley, 3.622% to 4/01/2030, FLR (SOFR + 3.12%) to 4/01/2031			41,896,000	45,879,526
Morgan Stanley, 3.217% to 4/22/2041, FLR (SOFR + 1.485%) to 4/22/2042			12,867,000	13,037,988
Royal Bank of Canada, 2.55%, 7/16/2024			29,154,000	30,870,315
Sumitomo Mitsui Financial Group, Inc., 1.71%, 1/12/2031			29,330,000	27,776,094
UBS Group AG, 3.126% to 8/13/2029, FLR (LIBOR - 3mo. + 1.468%) to 8/13/2030 (n)			14,856,000	15,642,349
UBS Group AG, 4.375% to 2/10/2031, FLR (CMT - 1yr. + 3.313%) to 8/10/2069 (n)			24,966,000	24,872,627
UniCredit S.p.A., 2.569% to 9/22/2025, FLR (CMT - 1yr. + 2.3%) to 9/22/2026 (n)			9,618,000	9,697,623
				$813,868,117
Medical & Health Technology & Services – 2.9%
Alcon, Inc., 2.6%, 5/27/2030 (n)		$	12,908,000	$    13,015,665
Alcon, Inc., 3.8%, 9/23/2049 (n)			5,170,000	5,463,261
Becton, Dickinson and Co., 3.734%, 12/15/2024			1,460,000	1,598,360
Becton, Dickinson and Co., 4.685%, 12/15/2044			7,796,000	9,361,336
Becton, Dickinson and Co., 4.669%, 6/06/2047			26,561,000	31,719,548
Cigna Corp., 3.2%, 3/15/2040			5,994,000	6,144,438
HCA, Inc., 4.75%, 5/01/2023			7,090,000	7,638,783
HCA, Inc., 5.25%, 6/15/2026			8,407,000	9,757,198
HCA, Inc., 5.875%, 2/01/2029			17,391,000	20,521,380
HCA, Inc., 3.5%, 9/01/2030			4,223,000	4,340,610
HCA, Inc., 5.125%, 6/15/2039			3,223,000	3,908,976
IQVIA Holdings, Inc., 5%, 5/15/2027 (n)			19,833,000	20,750,276

18

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Medical & Health Technology & Services – continued
Laboratory Corp. of America Holdings, 3.25%, 9/01/2024		$	7,129,000	$     7,633,083
Thermo Fisher Scientific, Inc., 2.95%, 9/19/2026			14,540,000	15,694,759
Thermo Fisher Scientific, Inc., 4.497%, 3/25/2030			20,000,000	23,438,791
				$180,986,464
Medical Equipment – 1.1%
Abbott Laboratories, 4.75%, 11/30/2036		$	13,256,000	$    16,594,198
Boston Scientific Corp., 3.75%, 3/01/2026			10,442,000	11,609,335
Boston Scientific Corp., 2.65%, 6/01/2030			9,471,000	9,597,703
Danaher Corp., 2.6%, 10/01/2050			19,542,000	17,449,836
Teleflex, Inc., 4.625%, 11/15/2027			2,045,000	2,174,817
Teleflex, Inc., 4.25%, 6/01/2028 (n)			7,259,000	7,494,917
				$64,920,806
Metals & Mining – 2.5%
Anglo American Capital PLC, 2.25%, 3/17/2028 (n)		$	11,184,000	$    11,121,253
Anglo American Capital PLC, 2.625%, 9/10/2030 (n)			22,275,000	21,958,435
Anglo American Capital PLC, 2.875%, 3/17/2031 (n)			13,073,000	13,104,349
FMG Resources Ltd., 4.375%, 4/01/2031 (n)			25,818,000	26,818,448
Freeport-McMoRan Copper & Gold, Inc., 4.625%, 8/01/2030			20,911,000	23,080,516
Glencore Funding LLC, 4.125%, 5/30/2023 (n)			11,974,000	12,754,944
Glencore Funding LLC, 2.5%, 9/01/2030 (n)			8,339,000	8,077,414
Glencore Funding LLC, 2.85%, 4/27/2031 (n)			17,132,000	16,891,175
Novelis Corp., 4.75%, 1/30/2030 (n)			21,900,000	22,776,000
				$156,582,534
Midstream – 3.6%
Cheniere Corpus Christi Holdings LLC, 3.7%, 11/15/2029		$	10,673,000	$    11,353,645
Energy Transfer Operating Co., 5%, 5/15/2050			10,704,000	11,280,487
Enterprise Products Operating LLC, 4.2%, 1/31/2050			22,476,000	24,106,323
Enterprise Products Operating LLC, 3.7%, 1/31/2051			26,285,000	26,247,311
Galaxy Pipeline Assets Bidco Ltd., 1.75%, 9/30/2027 (n)			37,604,000	37,780,392
Galaxy Pipeline Assets Bidco Ltd., 2.16%, 3/31/2034 (n)			13,951,000	13,681,390
MPLX LP, 4.5%, 4/15/2038			25,583,000	28,097,362
MPLX LP, 4.7%, 4/15/2048			1,686,000	1,843,944
Plains All American Pipeline LP/PAA Finance Corp., 4.65%, 10/15/2025			8,441,000	9,361,644
Plains All American Pipeline LP/PAA Finance Corp., 3.55%, 12/15/2029			13,128,000	13,308,081
Sabine Pass Liquefaction LLC, 5.875%, 6/30/2026			13,222,000	15,654,388
Sabine Pass Liquefaction LLC, 5%, 3/15/2027			5,405,000	6,213,573
Sabine Pass Liquefaction LLC, 4.2%, 3/15/2028			13,455,000	14,902,370

19

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Midstream – continued
Sabine Pass Liquefaction LLC, 4.5%, 5/15/2030		$	5,013,000	$     5,645,962
				$219,476,872
Mortgage-Backed – 0.0%
Freddie Mac, 3.244%, 8/25/2027		$	1,276,000	$     1,419,750
Municipals – 1.1%
Florida State Board of Administration Finance Corp. Rev., “A”, 1.705%, 7/01/2027		$	30,815,000	$    31,089,469
New Jersey Economic Development Authority State Pension Funding Rev., “A”, NPFG, 7.425%, 2/15/2029			29,000,000	37,372,187
				$68,461,656
Natural Gas - Distribution – 1.5%
NiSource Finance Corp., 4.8%, 2/15/2044		$	4,239,000	$     5,102,079
NiSource, Inc., 2.95%, 9/01/2029			27,307,000	28,376,448
NiSource, Inc., 5.65%, 2/01/2045			8,731,000	11,547,388
Sempra Energy, 3.25%, 6/15/2027			42,879,000	46,361,625
				$91,387,540
Natural Gas - Pipeline – 0.3%
APT Pipelines Ltd., 4.25%, 7/15/2027 (n)		$	5,122,000	$     5,711,210
APT Pipelines Ltd., 5%, 3/23/2035 (n)			12,850,000	15,203,599
				$20,914,809
Network & Telecom – 2.1%
AT&T, Inc., 2.75%, 6/01/2031		$	21,041,000	$    21,010,515
AT&T, Inc., 4.5%, 5/15/2035			13,000,000	14,740,094
AT&T, Inc., 3.55%, 9/15/2055 (n)			19,219,000	17,703,139
Verizon Communications, Inc., 2.1%, 3/22/2028			4,562,000	4,603,415
Verizon Communications, Inc., 3.15%, 3/22/2030			8,264,000	8,739,786
Verizon Communications, Inc., 4.812%, 3/15/2039			26,613,000	32,284,076
Verizon Communications, Inc., 3.4%, 3/22/2041			16,692,000	17,099,677
Verizon Communications, Inc., 4.522%, 9/15/2048			8,264,000	9,770,859
				$125,951,561
Oils – 0.9%
Puma International Financing S.A., 5%, 1/24/2026		$	17,131,000	$    17,242,352
Valero Energy Corp., 3.4%, 9/15/2026			20,305,000	21,758,428
Valero Energy Corp., 4.9%, 3/15/2045			17,086,000	19,444,271
				$58,445,051

20

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Other Banks & Diversified Financials – 0.3%
Groupe BPCE S.A., 4.5%, 3/15/2025 (n)		$	6,746,000	$     7,460,796
Mizrahi Tefahot Bank Ltd., 3.077% to 4/07/2026, FLR (CMT - 5yr. + 2.25%) to 4/07/2031 (n)			11,682,000	11,857,230
				$19,318,026
Personal Computers & Peripherals – 0.5%
Equifax, Inc., 2.6%, 12/01/2024		$	18,674,000	$    19,770,619
Equifax, Inc., 3.1%, 5/15/2030			12,869,000	13,518,563
				$33,289,182
Pollution Control – 0.8%
Republic Services, Inc., 2.5%, 8/15/2024		$	13,800,000	$    14,569,412
Republic Services, Inc., 3.95%, 5/15/2028			22,233,000	24,971,362
Republic Services, Inc., 1.45%, 2/15/2031			7,894,000	7,240,957
				$46,781,731
Railroad & Shipping – 0.3%
CSX Corp., 2.4%, 2/15/2030		$	18,044,000	$    18,249,872
Real Estate - Office – 0.7%
Boston Properties, Inc., REIT, 2.55%, 4/01/2032		$	30,669,000	$    29,659,341
Corporate Office Property LP, 2.75%, 4/15/2031			12,672,000	12,507,371
				$42,166,712
Real Estate - Other – 0.6%
Prologis LP, REIT, 2.25%, 4/15/2030		$	14,222,000	$    14,240,000
Prologis LP, REIT, 1.25%, 10/15/2030			12,857,000	11,844,104
Prologis LP, REIT, 2.125%, 10/15/2050			12,857,000	10,630,916
				$36,715,020
Real Estate - Retail – 1.5%
Brixmor Operating Partnership LP, REIT, 4.125%, 5/15/2029		$	3,022,000	$     3,321,118
Brixmor Operating Partnership LP, REIT, 4.05%, 7/01/2030			10,857,000	11,919,765
National Retail Properties, Inc., REIT, 3.5%, 4/15/2051			8,163,000	8,150,349
Spirit Realty, LP, 4.45%, 9/15/2026			8,428,000	9,404,366
Spirit Realty, LP, 3.2%, 2/15/2031			10,444,000	10,713,450
STORE Capital Corp., 4.5%, 3/15/2028			3,380,000	3,767,145
STORE Capital Corp., 4.625%, 3/15/2029			5,070,000	5,725,412
VEREIT Operating Partnership LP, REIT, 3.4%, 1/15/2028			8,424,000	9,112,216
VEREIT Operating Partnership LP, REIT, 3.1%, 12/15/2029			28,035,000	29,505,726
				$91,619,547

21

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Restaurants – 0.8%
Yum! Brands, Inc., 3.625%, 3/15/2031		$	30,692,000	$    30,293,311
Yum! Brands, Inc., 4.625%, 1/31/2032			17,506,000	18,297,271
				$48,590,582
Retailers – 1.7%
Alimentation Couche-Tard, Inc., 2.95%, 1/25/2030 (n)		$	9,114,000	$     9,357,471
Alimentation Couche-Tard, Inc., 3.8%, 1/25/2050 (n)			22,781,000	23,598,383
Costco Wholesale Corp., 1.6%, 4/20/2030			12,857,000	12,429,838
Home Depot, Inc., 3%, 4/01/2026			7,218,000	7,861,778
Home Depot, Inc., 3.3%, 4/15/2040			26,138,000	27,761,008
Home Depot, Inc., 4.875%, 2/15/2044			8,313,000	10,719,387
Kohl's Corp., 3.375%, 5/01/2031			10,276,000	10,491,309
				$102,219,174
Specialty Stores – 0.3%
Nordstrom, Inc., 4.25%, 8/01/2031 (n)		$	8,604,000	$     8,718,273
TJX Cos., Inc., 3.875%, 4/15/2030			8,351,000	9,399,681
				$18,117,954
Telecommunications - Wireless – 4.0%
American Tower Corp., REIT, 3%, 6/15/2023		$	19,876,000	$    20,876,069
American Tower Corp., REIT, 4%, 6/01/2025			12,172,000	13,452,356
American Tower Corp., REIT, 3.6%, 1/15/2028			21,944,000	23,961,558
American Tower Corp., REIT, 3.8%, 8/15/2029			10,621,000	11,689,675
Crown Castle International Corp., 3.15%, 7/15/2023			16,889,000	17,812,624
Crown Castle International Corp., 4.45%, 2/15/2026			15,364,000	17,374,204
Crown Castle International Corp., 4%, 3/01/2027			9,286,000	10,339,852
Crown Castle International Corp., 3.65%, 9/01/2027			8,862,000	9,725,767
Millicom International Cellular S.A., 4.5%, 4/27/2031 (n)			15,857,000	16,848,062
T-Mobile USA, Inc., 2.625%, 4/15/2026			17,214,000	17,510,081
T-Mobile USA, Inc., 4.75%, 2/01/2028			9,336,000	9,977,850
T-Mobile USA, Inc., 2.05%, 2/15/2028 (n)			22,896,000	22,726,570
T-Mobile USA, Inc., 3%, 2/15/2041 (n)			35,140,000	32,862,401
T-Mobile USA, Inc., 4.5%, 4/15/2050 (n)			17,667,000	19,925,019
				$245,082,088
Telephone Services – 0.7%
AT&T, Inc., 2.55%, 12/01/2033 (n)		$	21,405,000	$    20,402,174
Deutsche Telekom AG, 3.625%, 1/21/2050 (n)			21,146,000	21,800,860
				$42,203,034

22

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Bonds – continued
Transportation - Services – 0.3%
ERAC USA Finance LLC, 3.8%, 11/01/2025 (n)		$	9,848,000	$    10,851,002
ERAC USA Finance LLC, 7%, 10/15/2037 (n)			4,480,000	6,554,787
				$17,405,789
U.S. Treasury Obligations – 1.1%
U.S. Treasury Bonds, 3.5%, 2/15/2039 (f)		$	7,664,000	$     9,331,219
U.S. Treasury Bonds, 3%, 2/15/2048			50,009,800	57,274,896
				$66,606,115
Utilities - Electric Power – 6.6%
Berkshire Hathaway Energy Co., 4.5%, 2/01/2045		$	5,432,000	$     6,404,139
Duke Energy Carolinas LLC, 2.45%, 2/01/2030			27,869,000	28,395,852
Duke Energy Corp., 3.75%, 9/01/2046			34,756,000	35,895,754
Duke Energy Progress LLC, 3.45%, 3/15/2029			11,143,000	12,225,700
EDP Finance B.V., 3.625%, 7/15/2024 (n)			10,744,000	11,598,470
Enel Finance International N.V., 2.75%, 4/06/2023 (n)			34,129,000	35,482,659
Enel Finance International N.V., 2.65%, 9/10/2024			18,401,000	19,349,939
Enel Finance International N.V., 3.625%, 5/25/2027 (n)			8,585,000	9,350,947
Enel Finance International N.V., 4.75%, 5/25/2047 (n)			9,461,000	11,311,926
Evergy, Inc., 2.9%, 9/15/2029			30,865,000	31,730,763
Eversource Energy, 2.9%, 10/01/2024			9,093,000	9,679,147
FirstEnergy Corp., 4.4%, 7/15/2027			14,231,000	15,582,945
FirstEnergy Corp., 3.4%, 3/01/2050			29,978,000	27,654,705
Georgia Power Co., 3.7%, 1/30/2050			2,816,000	2,969,442
NextEra Energy Capital Holdings, Inc., 3.15%, 4/01/2024			11,886,000	12,736,710
NextEra Energy Capital Holdings, Inc., 3.55%, 5/01/2027			20,319,000	22,544,814
NextEra Energy Operating Co., 4.5%, 9/15/2027 (n)			12,862,000	13,884,786
NextEra Energy, Inc., 4.25%, 7/15/2024 (n)			6,958,000	7,375,480
Pacific Gas & Electric Co., 2.1%, 8/01/2027			13,953,000	13,602,172
PPL Capital Funding, Inc., 5%, 3/15/2044			3,193,000	3,944,367
Southern Co., 2.95%, 7/01/2023			6,880,000	7,199,482
Southern Co., 3.7%, 4/30/2030			31,250,000	34,114,680
Virginia Electric & Power Co., 2.875%, 7/15/2029			11,354,000	11,965,863
WEC Energy Group, Inc., 1.375%, 10/15/2027			17,576,000	17,081,636
				$402,082,378
Total Bonds (Identified Cost, $5,533,298,393)				$ 5,774,478,594

23

Portfolio of Investments – continued

Issuer			Shares/Par	Value ($)
Investment Companies (h) – 5.0%
Money Market Funds – 5.0%
MFS Institutional Money Market Portfolio, 0.04% (v) (Identified Cost, $307,167,790)			307,169,809	$   307,169,809
Other Assets, Less Liabilities – 0.8%				49,849,181
Net Assets – 100.0%				$ 6,131,497,584

    

(f)	All or a portion of the security has been segregated as collateral for open futures contracts.
(h)	An affiliated issuer, which may be considered one in which the fund owns 5% or more of the outstanding voting securities, or a company which is under common control. At period end, the aggregate values of the fund's investments in affiliated issuers and in unaffiliated issuers were $307,169,809 and $5,774,478,594, respectively.
(i)	Interest only security for which the fund receives interest on notional principal (Par amount). Par amount shown is the notional principal and does not reflect the cost of the security.
(n)	Securities exempt from registration under Rule 144A of the Securities Act of 1933. These securities may be sold in the ordinary course of business in transactions exempt from registration, normally to qualified institutional buyers. At period end, the aggregate value of these securities was $1,572,446,507, representing 25.6% of net assets.
(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualized seven-day yield of the fund at period end.

    

The following abbreviations are used in this report and are defined:
CMT	Constant Maturity Treasury
FLR	Floating Rate. Interest rate resets periodically based on the parenthetically disclosed reference rate plus a spread (if any). The period-end rate reported may not be the current rate. All reference rates are USD unless otherwise noted.
LIBOR	London Interbank Offered Rate
NPFG	National Public Finance Guarantee Corp.
REIT	Real Estate Investment Trust
SOFR	Secured Overnight Financing Rate

Derivative Contracts at 4/30/21

Futures Contracts
Description	Long/ Short	Currency	Contracts	Notional Amount	Expiration Date	Value/Unrealized Appreciation (Depreciation)
Asset Derivatives
Interest Rate Futures
U.S. Treasury Note 10 yr	Short	USD	2,765	$365,066,407	June – 2021	$5,822,241
U.S. Treasury Note 2 yr	Long	USD	1,060	234,003,281	June – 2021	2,898
U.S. Treasury Ultra Note 10 yr	Short	USD	2,150	312,925,781	June – 2021	7,146,824
						$12,971,963
Liability Derivatives
Interest Rate Futures
U.S. Treasury Ultra Bond	Long	USD	927	$172,335,094	June – 2021	$(3,675,210)

24

Portfolio of Investments – continued

At April 30, 2021, the fund had liquid securities with an aggregate value of $5,235,422 to cover any collateral or margin obligations for certain derivative contracts.

See Notes to Financial Statements

25

Financial Statements

Statement of Assets and Liabilities

At 4/30/21

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.

Assets
Investments in unaffiliated issuers, at value (identified cost, $5,533,298,393)	$5,774,478,594
Investments in affiliated issuers, at value (identified cost, $307,167,790)	307,169,809
Receivables for
Fund shares sold	13,737,538
Interest	47,716,168
Other assets	13,275
Total assets	$6,143,115,384
Liabilities
Payable to custodian	$132
Payables for
Distributions	781,859
Net daily variation margin on open futures contracts	108,676
Fund shares reacquired	8,802,582
Payable to affiliates
Investment adviser	121,870
Administrative services fee	3,089
Shareholder servicing costs	1,348,636
Distribution and service fees	41,139
Payable for independent Trustees' compensation	2,562
Accrued expenses and other liabilities	407,255
Total liabilities	$11,617,800
Net assets	$6,131,497,584
Net assets consist of
Paid-in capital	$5,818,826,960
Total distributable earnings (loss)	312,670,624
Net assets	$6,131,497,584
Shares of beneficial interest outstanding	406,654,557

26

Statement of Assets and Liabilities – continued

	Net assets	Shares outstanding	Net asset value per share (a)
Class A	$2,328,936,117	154,362,099	$15.09
Class B	10,838,293	719,776	15.06
Class C	98,956,010	6,579,677	15.04
Class I	1,573,250,261	104,379,706	15.07
Class R1	5,391,211	358,161	15.05
Class R2	28,348,310	1,878,634	15.09
Class R3	162,464,711	10,768,003	15.09
Class R4	73,889,776	4,895,786	15.09
Class R6	1,849,422,895	122,712,715	15.07

    

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Class A, for which the maximum offering price per share was $15.76 [100 / 95.75 x $15.09]. On sales of $100,000 or more, the maximum offering price of Class A shares is reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, and Class C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, and R6.

See Notes to Financial Statements

27

Financial Statements

Statement of Operations

Year ended 4/30/21

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.

Net investment income (loss)
Income
Interest	$186,401,204
Other	260,695
Dividends from affiliated issuers	237,468
Foreign taxes withheld	(4,194)
Total investment income	$186,895,173
Expenses
Management fee	$22,233,790
Distribution and service fees	7,711,991
Shareholder servicing costs	4,572,425
Administrative services fee	559,026
Independent Trustees' compensation	54,614
Custodian fee	227,620
Shareholder communications	556,750
Audit and tax fees	78,549
Legal fees	45,744
Miscellaneous	555,557
Total expenses	$36,596,066
Fees paid indirectly	(261)
Reduction of expenses by investment adviser and distributor	(681,481)
Net expenses	$35,914,324
Net investment income (loss)	$150,980,849
Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers	$128,307,423
Affiliated issuers	(11,195)
Futures contracts	(10,628,813)
Net realized gain (loss)	$117,667,415
Change in unrealized appreciation or depreciation
Unaffiliated issuers	$(33,900,668)
Affiliated issuers	(4,510)
Futures contracts	12,318,324
Net unrealized gain (loss)	$(21,586,854)
Net realized and unrealized gain (loss)	$96,080,561
Change in net assets from operations	$247,061,410

See Notes to Financial Statements

28

Financial Statements

Statements of Changes in Net Assets

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.

	Year ended
	4/30/21	4/30/20
Change in net assets
From operations
Net investment income (loss)	$150,980,849	$140,317,384
Net realized gain (loss)	117,667,415	83,364,143
Net unrealized gain (loss)	(21,586,854)	205,073,305
Change in net assets from operations	$247,061,410	$428,754,832
Total distributions to shareholders	$(213,247,208)	$(142,294,173)
Change in net assets from fund share transactions	$1,095,252,049	$544,665,462
Total change in net assets	$1,129,066,251	$831,126,121
Net assets
At beginning of period	5,002,431,333	4,171,305,212
At end of period	$6,131,497,584	$5,002,431,333

See Notes to Financial Statements

29

Financial Statements

Financial Highlights

The financial highlights table is intended to help you understand the fund's financial performance for the past 5 years. Certain information reflects financial results for a single fund share. The total returns in the table represent the rate that an investor would have earned (or lost) on an investment in the fund share class (assuming reinvestment of all distributions) held for the entire period.

Class A	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.88	$13.93	$13.52	$13.92	$13.99
Income (loss) from investment operations
Net investment income (loss) (d)	$0.37	$0.42	$0.43	$0.41	$0.42(c)
Net realized and unrealized gain (loss)	0.37	0.96	0.41	(0.39)	(0.04)
Total from investment operations	$0.74	$1.38	$0.84	$0.02	$0.38
Less distributions declared to shareholders
From net investment income	$(0.39)	$(0.43)	$(0.43)	$(0.42)	$(0.45)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.53)	$(0.43)	$(0.43)	$(0.42)	$(0.45)
Net asset value, end of period (x)	$15.09	$14.88	$13.93	$13.52	$13.92
Total return (%) (r)(s)(t)(x)	4.94	10.00	6.39	0.08	2.73(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	0.77	0.79	0.79	0.80	0.81(c)
Expenses after expense reductions (f)	0.75	0.77	0.78	0.79	0.80(c)
Net investment income (loss)	2.42	2.91	3.16	2.95	3.04(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$2,328,936	$1,996,170	$1,654,534	$1,648,508	$1,597,201

See Notes to Financial Statements

30

Financial Highlights – continued

Class B	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.85	$13.90	$13.50	$13.89	$13.96
Income (loss) from investment operations
Net investment income (loss) (d)	$0.26	$0.32	$0.32	$0.31	$0.32(c)
Net realized and unrealized gain (loss)	0.36	0.95	0.41	(0.39)	(0.05)
Total from investment operations	$0.62	$1.27	$0.73	$(0.08)	$0.27
Less distributions declared to shareholders
From net investment income	$(0.27)	$(0.32)	$(0.33)	$(0.31)	$(0.34)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.41)	$(0.32)	$(0.33)	$(0.31)	$(0.34)
Net asset value, end of period (x)	$15.06	$14.85	$13.90	$13.50	$13.89
Total return (%) (r)(s)(t)(x)	4.17	9.20	5.53	(0.60)	1.96(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	1.52	1.54	1.54	1.55	1.56(c)
Expenses after expense reductions (f)	1.50	1.53	1.53	1.54	1.55(c)
Net investment income (loss)	1.70	2.18	2.41	2.20	2.30(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$10,838	$21,384	$33,983	$47,698	$61,123

See Notes to Financial Statements

31

Financial Highlights – continued

Class C	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.84	$13.89	$13.48	$13.88	$13.94
Income (loss) from investment operations
Net investment income (loss) (d)	$0.26	$0.31	$0.32	$0.31	$0.32(c)
Net realized and unrealized gain (loss)	0.35	0.96	0.42	(0.40)	(0.04)
Total from investment operations	$0.61	$1.27	$0.74	$(0.09)	$0.28
Less distributions declared to shareholders
From net investment income	$(0.27)	$(0.32)	$(0.33)	$(0.31)	$(0.34)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.41)	$(0.32)	$(0.33)	$(0.31)	$(0.34)
Net asset value, end of period (x)	$15.04	$14.84	$13.89	$13.48	$13.88
Total return (%) (r)(s)(t)(x)	4.10	9.21	5.61	(0.67)	2.04(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	1.51	1.54	1.54	1.55	1.56(c)
Expenses after expense reductions (f)	1.50	1.53	1.53	1.54	1.56(c)
Net investment income (loss)	1.68	2.16	2.41	2.20	2.30(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$98,956	$143,988	$143,872	$182,315	$242,889

See Notes to Financial Statements

32

Financial Highlights – continued

Class I	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.87	$13.92	$13.51	$13.91	$13.98
Income (loss) from investment operations
Net investment income (loss) (d)	$0.41	$0.46	$0.46	$0.45	$0.45(c)
Net realized and unrealized gain (loss)	0.36	0.96	0.42	(0.40)	(0.04)
Total from investment operations	$0.77	$1.42	$0.88	$0.05	$0.41
Less distributions declared to shareholders
From net investment income	$(0.43)	$(0.47)	$(0.47)	$(0.45)	$(0.48)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.57)	$(0.47)	$(0.47)	$(0.45)	$(0.48)
Net asset value, end of period (x)	$15.07	$14.87	$13.92	$13.51	$13.91
Total return (%) (r)(s)(t)(x)	5.14	10.28	6.66	0.33	2.99(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	0.52	0.53	0.54	0.55	0.56(c)
Expenses after expense reductions (f)	0.50	0.52	0.53	0.54	0.56(c)
Net investment income (loss)	2.66	3.15	3.40	3.19	3.25(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$1,573,250	$1,306,407	$1,021,313	$1,781,450	$2,005,193

See Notes to Financial Statements

33

Financial Highlights – continued

Class R1	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.85	$13.90	$13.49	$13.89	$13.95
Income (loss) from investment operations
Net investment income (loss) (d)	$0.26	$0.31	$0.32	$0.31	$0.32(c)
Net realized and unrealized gain (loss)	0.35	0.96	0.42	(0.40)	(0.04)
Total from investment operations	$0.61	$1.27	$0.74	$(0.09)	$0.28
Less distributions declared to shareholders
From net investment income	$(0.27)	$(0.32)	$(0.33)	$(0.31)	$(0.34)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.41)	$(0.32)	$(0.33)	$(0.31)	$(0.34)
Net asset value, end of period (x)	$15.05	$14.85	$13.90	$13.49	$13.89
Total return (%) (r)(s)(t)(x)	4.10	9.20	5.60	(0.67)	2.04(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	1.51	1.54	1.54	1.55	1.56(c)
Expenses after expense reductions (f)	1.50	1.53	1.53	1.54	1.56(c)
Net investment income (loss)	1.68	2.16	2.41	2.20	2.30(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$5,391	$5,970	$6,187	$6,101	$6,780

See Notes to Financial Statements

34

Financial Highlights – continued

Class R2	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.88	$13.93	$13.53	$13.92	$13.99
Income (loss) from investment operations
Net investment income (loss) (d)	$0.34	$0.39	$0.39	$0.38	$0.39(c)
Net realized and unrealized gain (loss)	0.36	0.95	0.41	(0.39)	(0.05)
Total from investment operations	$0.70	$1.34	$0.80	$(0.01)	$0.34
Less distributions declared to shareholders
From net investment income	$(0.35)	$(0.39)	$(0.40)	$(0.38)	$(0.41)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.49)	$(0.39)	$(0.40)	$(0.38)	$(0.41)
Net asset value, end of period (x)	$15.09	$14.88	$13.93	$13.53	$13.92
Total return (%) (r)(s)(t)(x)	4.68	9.73	6.05	(0.09)	2.47(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	1.02	1.04	1.04	1.05	1.06(c)
Expenses after expense reductions (f)	1.00	1.03	1.03	1.04	1.05(c)
Net investment income (loss)	2.18	2.67	2.91	2.70	2.79(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$28,348	$31,346	$38,593	$43,827	$49,948

See Notes to Financial Statements

35

Financial Highlights – continued

Class R3	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.88	$13.93	$13.52	$13.92	$13.99
Income (loss) from investment operations
Net investment income (loss) (d)	$0.37	$0.42	$0.43	$0.41	$0.43(c)
Net realized and unrealized gain (loss)	0.37	0.96	0.41	(0.39)	(0.05)
Total from investment operations	$0.74	$1.38	$0.84	$0.02	$0.38
Less distributions declared to shareholders
From net investment income	$(0.39)	$(0.43)	$(0.43)	$(0.42)	$(0.45)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.53)	$(0.43)	$(0.43)	$(0.42)	$(0.45)
Net asset value, end of period (x)	$15.09	$14.88	$13.93	$13.52	$13.92
Total return (%) (r)(s)(t)(x)	4.94	10.00	6.39	0.08	2.73(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	0.77	0.79	0.79	0.81	0.81(c)
Expenses after expense reductions (f)	0.75	0.78	0.78	0.80	0.80(c)
Net investment income (loss)	2.43	2.91	3.16	2.95	3.04(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$162,465	$165,319	$163,142	$167,404	$61,292

See Notes to Financial Statements

36

Financial Highlights – continued

Class R4	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.89	$13.93	$13.53	$13.93	$13.99
Income (loss) from investment operations
Net investment income (loss) (d)	$0.41	$0.46	$0.46	$0.45	$0.46(c)
Net realized and unrealized gain (loss)	0.36	0.97	0.41	(0.40)	(0.04)
Total from investment operations	$0.77	$1.43	$0.87	$0.05	$0.42
Less distributions declared to shareholders
From net investment income	$(0.43)	$(0.47)	$(0.47)	$(0.45)	$(0.48)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.57)	$(0.47)	$(0.47)	$(0.45)	$(0.48)
Net asset value, end of period (x)	$15.09	$14.89	$13.93	$13.53	$13.93
Total return (%) (r)(s)(t)(x)	5.13	10.35	6.57	0.33	3.06(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	0.52	0.53	0.54	0.55	0.56(c)
Expenses after expense reductions (f)	0.50	0.52	0.53	0.54	0.56(c)
Net investment income (loss)	2.67	3.17	3.41	3.19	3.29(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$73,890	$63,775	$75,519	$74,027	$169,661

See Notes to Financial Statements

37

Financial Highlights – continued

Class R6	Year ended
	4/30/21	4/30/20	4/30/19	4/30/18	4/30/17
Net asset value, beginning of period	$14.87	$13.92	$13.51	$13.91	$13.98
Income (loss) from investment operations
Net investment income (loss) (d)	$0.42	$0.47	$0.47	$0.46	$0.47(c)
Net realized and unrealized gain (loss)	0.36	0.96	0.42	(0.39)	(0.04)
Total from investment operations	$0.78	$1.43	$0.89	$0.07	$0.43
Less distributions declared to shareholders
From net investment income	$(0.44)	$(0.48)	$(0.48)	$(0.47)	$(0.50)
From net realized gain	(0.14)	—	—	—	—
Total distributions declared to shareholders	$(0.58)	$(0.48)	$(0.48)	$(0.47)	$(0.50)
Net asset value, end of period (x)	$15.07	$14.87	$13.92	$13.51	$13.91
Total return (%) (r)(s)(t)(x)	5.23	10.38	6.76	0.43	3.09(c)
Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)	0.42	0.44	0.44	0.45	0.46(c)
Expenses after expense reductions (f)	0.41	0.43	0.43	0.44	0.45(c)
Net investment income (loss)	2.76	3.25	3.51	3.27	3.39(c)
Portfolio turnover	37	36	38	38	28
Net assets at end of period (000 omitted)	$1,849,423	$1,268,071	$1,034,161	$1,043,950	$58,575

    

(c)	Amount reflects a one-time reimbursement of expenses by the custodian (or former custodian) without which net investment income and performance would be lower and expenses would be higher.
(d)	Per share data is based on average shares outstanding.
(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.
(r)	Certain expenses have been reduced without which performance would have been lower.
(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.
(t)	Total returns do not include any applicable sales charges.
(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

38

Notes to Financial Statements

(1) Business and Organization

MFS Corporate Bond Fund (the fund) is a diversified series of MFS Series Trust IX (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as an open-end management investment company.

The fund is an investment company and accordingly follows the investment company accounting and reporting guidance of the Financial Accounting Standards Board (FASB) Accounting Standards Codification Topic 946 Financial Services - Investment Companies.

(2) Significant Accounting Policies

General — The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. In the preparation of these financial statements, management has evaluated subsequent events occurring after the date of the fund’s Statement of Assets and Liabilities through the date that the financial statements were issued. The fund invests in high-yield securities rated below investment grade. Investments in below investment grade quality securities can involve a substantially greater risk of default or can already be in default, and their values can decline significantly. Below investment grade quality securities tend to be more sensitive to adverse news about the issuer, or the market or economy in general, than higher quality debt instruments. The fund invests in foreign securities. Investments in foreign securities are vulnerable to the effects of changes in the relative values of the local currency and the U.S. dollar and to the effects of changes in each country’s market, economic, industrial, political, regulatory, geopolitical, environmental, public health, and other conditions.

In March 2020, the FASB issued Accounting Standards Update 2020-04, Reference Rate Reform (Topic 848) – Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”), which provides optional, temporary relief for certain reference rate-related contract modifications due to the planned discontinuation of the London Interbank Offered Rate (LIBOR) and other IBOR-based reference rates as of the end of 2021. In March 2021, the administrator for LIBOR announced the extension of the publication of the more commonly used U.S. dollar LIBOR settings to the end of June 2023. Management is still evaluating the impact of ASU 2020-04 on the fund's accounting for investments, derivatives, debt and other contracts that will undergo reference rate-related modifications as a result of the reference rate reform.

Balance Sheet Offsetting — The fund's accounting policy with respect to balance sheet offsetting is that, absent an event of default by the counterparty or a termination of the agreement, the International Swaps and Derivatives Association (ISDA) Master Agreement, or similar agreement, does not result in an offset of reported amounts of financial assets and financial liabilities in the Statement of Assets and Liabilities across transactions between the fund and the applicable counterparty. The fund's right to setoff may be restricted or prohibited by the bankruptcy or insolvency laws of the particular jurisdiction to which a specific master netting agreement counterparty is

39

Notes to Financial Statements  - continued

subject. Balance sheet offsetting disclosures, to the extent applicable to the fund, have been included in the fund’s Significant Accounting Policies note under the captions for each of the fund’s in-scope financial instruments and transactions.

Investment Valuations — Debt instruments and floating rate loans, including restricted debt instruments, are generally valued at an evaluated or composite bid as provided by a third-party pricing service. Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value. Futures contracts are generally valued at last posted settlement price on their primary exchange as provided by a third-party pricing service. Futures contracts for which there were no trades that day for a particular position are generally valued at the closing bid quotation on their primary exchange as provided by a third-party pricing service. Open-end investment companies are generally valued at net asset value per share. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data. The values of foreign securities and other assets and liabilities expressed in foreign currencies are converted to U.S. dollars using the mean of bid and asked prices for rates provided by a third-party pricing service.

The Board of Trustees has delegated primary responsibility for determining or causing to be determined the value of the fund’s investments (including any fair valuation) to the adviser pursuant to valuation policies and procedures approved by the Board. If the adviser determines that reliable market quotations are not readily available, investments are valued at fair value as determined in good faith by the adviser in accordance with such procedures under the oversight of the Board of Trustees. Under the fund’s valuation policies and procedures, market quotations are not considered to be readily available for most types of debt instruments and floating rate loans and many types of derivatives. These investments are generally valued at fair value based on information from third-party pricing services. In addition, investments may be valued at fair value if the adviser determines that an investment’s value has been materially affected by events occurring after the close of the exchange or market on which the investment is principally traded (such as foreign exchange or market) and prior to the determination of the fund’s net asset value, or after the halt of trading of a specific security where trading does not resume prior to the close of the exchange or market on which the security is principally traded. The adviser generally relies on third-party pricing services or other information (such as the correlation with price movements of similar securities in the same or other markets; the type, cost and investment characteristics of the security; the business and financial condition of the issuer; and trading and other market data) to assist in determining whether to fair value and at what value to fair value an investment. The value of an investment for purposes of calculating the fund’s net asset value can differ depending on the source and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.

Various inputs are used in determining the value of the fund's assets or liabilities. These inputs are categorized into three broad levels. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases,

40

Notes to Financial Statements  - continued

an investment's level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The fund's assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the investment. Level 1 includes unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 includes other significant observable market-based inputs (including quoted prices for similar securities, interest rates, prepayment speed, and credit risk). Level 3 includes unobservable inputs, which may include the adviser's own assumptions in determining the fair value of investments. Other financial instruments are derivative instruments, such as futures contracts. The following is a summary of the levels used as of April 30, 2021 in valuing the fund's assets or liabilities:

Financial Instruments	Level 1	Level 2	Level 3	Total
U.S. Treasury Bonds & U.S. Government Agencies & Equivalents	$—	$66,606,115	$—	$66,606,115
Non - U.S. Sovereign Debt	—	80,939,487	—	80,939,487
Municipal Bonds	—	68,461,656	—	68,461,656
U.S. Corporate Bonds	—	4,321,423,547	—	4,321,423,547
Residential Mortgage-Backed Securities	—	1,419,750	—	1,419,750
Commercial Mortgage-Backed Securities	—	571,605	—	571,605
Asset-Backed Securities (including CDOs)	—	573,186	—	573,186
Foreign Bonds	—	1,234,483,248	—	1,234,483,248
Mutual Funds	307,169,809	—	—	307,169,809
Total	$307,169,809	$5,774,478,594	$—	$6,081,648,403
Other Financial Instruments
Futures Contracts – Assets	$12,971,963	$—	$—	$12,971,963
Futures Contracts – Liabilities	(3,675,210)	—	—	(3,675,210)

For further information regarding security characteristics, see the Portfolio of Investments.

Derivatives — The fund uses derivatives primarily to increase or decrease exposure to a particular market or segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. Derivatives are used for hedging or non-hedging purposes. While hedging can reduce or eliminate losses, it can also reduce or eliminate gains. When the fund uses derivatives as an investment to increase market exposure, or for hedging purposes, gains and losses from derivative instruments may be substantially greater than the derivative’s original cost.

The derivative instruments used by the fund during the period were futures contracts. Depending on the type of derivative, a fund may exit a derivative position by entering into an offsetting transaction with a counterparty or exchange, negotiating an agreement with the derivative counterparty, or novating the position to a third party. The fund may be unable to promptly close out a futures position in instances where the daily fluctuation in the price for that type of future exceeds the daily limit set by the

41

Notes to Financial Statements  - continued

exchange. The fund's period end derivatives, as presented in the Portfolio of Investments and the associated Derivative Contract tables, generally are indicative of the volume of its derivative activity during the period.

The following table presents, by major type of derivative contract, the fair value, on a gross basis, of the asset and liability components of derivatives held by the fund at April 30, 2021 as reported in the Statement of Assets and Liabilities:

		Fair Value (a)
Risk	Derivative Contracts	Asset Derivatives	Liability Derivatives
Interest Rate	Interest Rate Futures	$12,971,963	$(3,675,210)

(a)	Values presented in this table for futures contracts correspond to the values reported in the Portfolio of Investments. Only the current day net variation margin for futures contracts is separately reported within the Statement of Assets and Liabilities.

The following table presents, by major type of derivative contract, the realized gain (loss) on derivatives held by the fund for the year ended April 30, 2021 as reported in the Statement of Operations:

Risk	Futures Contracts
Interest Rate	$(10,628,813)

The following table presents, by major type of derivative contract, the change in unrealized appreciation or depreciation on derivatives held by the fund for the year ended April 30, 2021 as reported in the Statement of Operations:

Risk	Futures Contracts
Interest Rate	$12,318,324

Derivative counterparty credit risk is managed through formal evaluation of the creditworthiness of all potential counterparties. On certain, but not all, uncleared derivatives, the fund attempts to reduce its exposure to counterparty credit risk whenever possible by entering into an ISDA Master Agreement on a bilateral basis. The ISDA Master Agreement gives each party to the agreement the right to terminate all transactions traded under such agreement if there is a specified deterioration in the credit quality of the other party. Upon an event of default or a termination of the ISDA Master Agreement, the non-defaulting party has the right to close out all transactions traded under such agreement and to net amounts owed under each agreement to one net amount payable by one party to the other. This right to close out and net payments across all transactions traded under the ISDA Master Agreement could result in a reduction of the fund's credit risk to such counterparty equal to any amounts payable by the fund under the applicable transactions, if any.

Collateral and margin requirements differ by type of derivative. For cleared derivatives (e.g., futures contracts, cleared swaps, and exchange-traded options), margin requirements are set by the clearing broker and the clearing house and collateral, in the form of cash or securities, is posted by the fund directly with the clearing broker. Collateral terms are counterparty agreement specific for uncleared derivatives (e.g., forward foreign currency exchange contracts, uncleared swap agreements, and uncleared options) and collateral, in the form of cash and securities, is held in segregated accounts with the fund's custodian in connection with these agreements.

42

Notes to Financial Statements  - continued

For derivatives traded under an ISDA Master Agreement, which contains a collateral support annex, the collateral requirements are netted across all transactions traded under such counterparty-specific agreement and an amount is posted from one party to the other to collateralize such obligations. Cash that has been segregated or delivered to cover the fund's collateral or margin obligations under derivative contracts, if any, will be reported separately in the Statement of Assets and Liabilities as restricted cash for uncleared derivatives and/or deposits with brokers for cleared derivatives. Securities pledged as collateral or margin for the same purpose, if any, are noted in the Portfolio of Investments. The fund may be required to make payments of interest on uncovered collateral or margin obligations with the broker. Any such payments are included in “Miscellaneous” expense in the Statement of Operations.

Futures Contracts — The fund entered into futures contracts which may be used to hedge against or obtain broad market exposure, interest rate exposure, currency exposure, or to manage duration. A futures contract represents a commitment for the future purchase or sale of an asset at a specified price on a specified date.

Upon entering into a futures contract, the fund is required to deposit with the broker, either in cash or securities, an initial margin in an amount equal to a specified percentage of the notional amount of the contract. Subsequent payments (variation margin) are made or received by the fund each day, depending on the daily fluctuations in the value of the contract, and are recorded for financial statement purposes as unrealized gain or loss by the fund until the contract is closed or expires at which point the gain or loss on futures contracts is realized.

The fund bears the risk of interest rates, exchange rates or securities prices moving unexpectedly, in which case, the fund may not achieve the anticipated benefits of the futures contracts and may realize a loss. While futures contracts may present less counterparty risk to the fund since the contracts are exchange traded and the exchange’s clearinghouse guarantees payments to the broker, there is still counterparty credit risk due to the insolvency of the broker. The fund’s maximum risk of loss due to counterparty credit risk is equal to the margin posted by the fund to the broker plus any gains or minus any losses on the outstanding futures contracts.

Indemnifications — Under the fund's organizational documents, its officers and Trustees may be indemnified against certain liabilities and expenses arising out of the performance of their duties to the fund. Additionally, in the normal course of business, the fund enters into agreements with service providers that may contain indemnification clauses. The fund's maximum exposure under these agreements is unknown as this would involve future claims that may be made against the fund that have not yet occurred.

Investment Transactions and Income — Investment transactions are recorded on the trade date. Interest income is recorded on the accrual basis. All premium and discount is amortized or accreted for financial statement purposes in accordance with U.S. generally accepted accounting principles. Interest payments received in additional securities are recorded on the ex-interest date in an amount equal to the value of the security on such date.

43

Notes to Financial Statements  - continued

The fund may receive proceeds from litigation settlements. Any proceeds received from litigation involving portfolio holdings are reflected in the Statement of Operations in realized gain/loss if the security has been disposed of by the fund or in unrealized gain/loss if the security is still held by the fund. Any other proceeds from litigation not related to portfolio holdings are reflected as other income in the Statement of Operations.

Fees Paid Indirectly — The fund's custody fee may be reduced by a credit earned under an arrangement that measures the value of U.S. dollars deposited with the custodian by the fund. The amount of the credit, for the year ended April 30, 2021, is shown as a reduction of total expenses in the Statement of Operations.

Tax Matters and Distributions — The fund intends to qualify as a regulated investment company, as defined under Subchapter M of the Internal Revenue Code, and to distribute all of its taxable income, including realized capital gains. As a result, no provision for federal income tax is required. The fund’s federal tax returns, when filed, will remain subject to examination by the Internal Revenue Service for a three year period. Management has analyzed the fund’s tax positions taken on federal and state tax returns for all open tax years and does not believe that there are any uncertain tax positions that require recognition of a tax liability. Foreign taxes, if any, have been accrued by the fund in the accompanying financial statements in accordance with the applicable foreign tax law. Foreign income taxes may be withheld by certain countries in which the fund invests. Additionally, capital gains realized by the fund on securities issued in or by certain foreign countries may be subject to capital gains tax imposed by those countries.

Distributions to shareholders are recorded on the ex-dividend date. Income and capital gain distributions are determined in accordance with income tax regulations, which may differ from U.S. generally accepted accounting principles. Certain capital accounts in the financial statements are periodically adjusted for permanent differences in order to reflect their tax character. These adjustments have no impact on net assets or net asset value per share. Temporary differences which arise from recognizing certain items of income, expense, gain or loss in different periods for financial statement and tax purposes will reverse at some time in the future.

Book/tax differences primarily relate to amortization and accretion of debt securities, derivative transactions, and treating a portion of the proceeds from redemptions as a distribution for tax purposes.

The tax character of distributions declared to shareholders for the last two fiscal years is as follows:

	Year ended 4/30/21	Year ended 4/30/20
Ordinary income (including any short-term capital gains)	$168,243,271	$142,294,173
Long-term capital gains	45,003,937	—
Total distributions	$213,247,208	$142,294,173

44

Notes to Financial Statements  - continued

The federal tax cost and the tax basis components of distributable earnings were as follows:

As of 4/30/21
Cost of investments	$5,854,963,839
Gross appreciation	306,799,786
Gross depreciation	(70,818,469)
Net unrealized appreciation (depreciation)	$ 235,981,317
Undistributed ordinary income	23,137,879
Undistributed long-term capital gain	66,991,550
Other temporary differences	(13,440,122)
Total distributable earnings (loss)	$ 312,670,624

Multiple Classes of Shares of Beneficial Interest — The fund offers multiple classes of shares, which differ in their respective distribution and service fees. The fund's income and common expenses are allocated to shareholders based on the value of settled shares outstanding of each class. The fund's realized and unrealized gain (loss) are allocated to shareholders based on the daily net assets of each class. Dividends are declared separately for each class. Differences in per share dividend rates are generally due to differences in separate class expenses. Class B and Class C shares will convert to Class A shares approximately eight years after purchase. The fund’s distributions declared to shareholders as reported in the Statements of Changes in Net Assets are presented by class as follows:

	Year ended 4/30/21		Year ended 4/30/20
Class A	$78,125,541		$54,493,969
Class B	393,206		653,854
Class C	3,564,955		3,216,758
Class I	60,865,875		37,011,421
Class R1	154,863		147,830
Class R2	1,039,164		972,399
Class R3	5,722,108		4,962,249
Class R4	2,622,912		2,351,769
Class R6	60,758,584		38,483,924
Total	$213,247,208		$142,294,173

(3) Transactions with Affiliates

Investment Adviser — The fund has an investment advisory agreement with MFS to provide overall investment management and related administrative services and facilities to the fund. The management fee is computed daily and paid monthly at the following annual rates based on the fund's average daily net assets:

Up to $1.1 billion	0.39%
In excess of $1.1 billion and up to $5 billion	0.38%
In excess of $5 billion and up to $10 billion	0.35%
In excess of $10 billion	0.34%

45

Notes to Financial Statements  - continued

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund's Board of Trustees. For the year ended April 30, 2021, this management fee reduction amounted to $665,412, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the year ended April 30, 2021 was equivalent to an annual effective rate of 0.37% of the fund's average daily net assets.

Distributor — MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $165,394 for the year ended April 30, 2021, as its portion of the initial sales charge on sales of Class A shares of the fund.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule 12b-1 of the Investment Company Act of 1940.

The fund's distribution plan provides that the fund will pay MFD for services provided by MFD and financial intermediaries in connection with the distribution and servicing of certain share classes. One component of the plan is a distribution fee paid to MFD and another component of the plan is a service fee paid to MFD. MFD may subsequently pay all, or a portion, of the distribution and/or service fees to financial intermediaries.

Distribution Plan Fee Table:

	Distribution Fee Rate (d)	Service Fee Rate (d)	Total Distribution Plan (d)	Annual Effective Rate (e)	Distribution and Service Fee
Class A	—	0.25%	0.25%	0.25%	$ 5,635,831
Class B	0.75%	0.25%	1.00%	1.00%	149,578
Class C	0.75%	0.25%	1.00%	1.00%	1,290,326
Class R1	0.75%	0.25%	1.00%	1.00%	58,014
Class R2	0.25%	0.25%	0.50%	0.50%	161,344
Class R3	—	0.25%	0.25%	0.25%	416,898
Total Distribution and Service Fees					$7,711,991

(d)

In accordance with the distribution plan for certain classes, the fund pays distribution and/or service fees equal to these annual percentage rates of each class’s average daily net assets. The distribution and service fee rates disclosed by class represent the current rates in effect at the end of the reporting period. Any rate changes, if applicable, are detailed below.

(e)

The annual effective rates represent actual fees incurred under the distribution plan for the year ended April 30, 2021 based on each class's average daily net assets. MFD has voluntarily agreed to rebate a portion of each class's 0.25% service fee attributable to accounts for which there is no financial intermediary specified on the account except for accounts attributable to MFS or its affiliates' seed money. For the year ended April 30, 2021, this rebate amounted to $15,732, $71, $183, $65, and $18 for Class A, Class B, Class C, Class R2, and Class R3, respectively, and is included in the reduction of total expenses in the Statement of Operations.

Certain Class A shares are subject to a contingent deferred sales charge (CDSC) in the event of a shareholder redemption within 18 months of purchase. Class B shares are subject to a CDSC in the event of a shareholder redemption within six years of

46

Notes to Financial Statements  - continued

purchase. Class C shares are subject to a CDSC in the event of a shareholder redemption within 12 months of purchase. All contingent deferred sales charges are paid to MFD and during the year ended April 30, 2021, were as follows:

	Amount
Class A	$63,369
Class B	11,195
Class C	17,548

Shareholder Servicing Agent — MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund's Board of Trustees. For the year ended April 30, 2021, the fee was $387,393, which equated to 0.0066% annually of the fund's average daily net assets. MFSC also receives reimbursement from the fund for out-of-pocket expenses, sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incur sub-accounting fees. For the year ended April 30, 2021, these out-of-pocket expenses, sub-accounting and other shareholder servicing costs amounted to $4,185,032.

Administrator — MFS provides certain financial, legal, shareholder communications, compliance, and other administrative services to the fund. Under an administrative services agreement, the fund reimburses MFS the costs incurred to provide these services. The fund is charged an annual fixed amount of $17,500 plus a fee based on average daily net assets. The administrative services fee incurred for the year ended April 30, 2021 was equivalent to an annual effective rate of 0.0095% of the fund's average daily net assets.

Trustees’ and Officers’ Compensation — The fund pays compensation to independent Trustees in the form of a retainer, attendance fees, and additional compensation to Board and Committee chairpersons. The fund does not pay compensation directly to Trustees or officers of the fund who are also officers of the investment adviser, all of whom receive remuneration from MFS for their services to the fund. Certain officers and Trustees of the fund are officers or directors of MFS, MFD, and MFSC.

Prior to December 31, 2001, the fund had an unfunded defined benefit plan (“DB plan”) for independent Trustees. As of December 31, 2001, the Board took action to terminate the DB plan with respect to then-current and any future independent Trustees, such that the DB plan covers only certain of those former independent Trustees who retired on or before December 31, 2001. The DB plan resulted in a pension expense of $268 and is included in “Independent Trustees’ compensation” in the Statement of Operations for the year ended April 30, 2021. The liability for deferred retirement benefits payable to those former independent Trustees under the DB plan amounted to $2,089 at April 30, 2021, and is included in “Payable for independent Trustees’ compensation” in the Statement of Assets and Liabilities.

Other — The fund invests in the MFS Institutional Money Market Portfolio which is managed by MFS and seeks current income consistent with preservation of capital and liquidity. This money market fund does not pay a management fee to MFS but does incur investment and operating costs.

47

Notes to Financial Statements  - continued

(4) Portfolio Securities

For the year ended April 30, 2021, purchases and sales of investments, other than short-term obligations, were as follows:

	Purchases	Sales
U.S. Government securities	$80,332,934	$109,890,758
Non-U.S. Government securities	2,782,204,983	1,967,279,580

(5) Shares of Beneficial Interest

The fund's Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:

	Year ended 4/30/21			Year ended 4/30/20
	Shares	Amount		Shares	Amount
Shares sold
Class A	43,635,190	$676,214,608		38,718,178	$565,408,533
Class B	53,975	834,669		80,249	1,160,198
Class C	1,942,767	29,996,702		2,116,568	30,814,940
Class I	56,393,302	871,029,240		42,528,281	617,067,106
Class R1	122,243	1,873,848		131,587	1,911,136
Class R2	584,800	9,068,152		667,849	9,745,645
Class R3	3,050,546	47,134,025		3,012,382	44,042,540
Class R4	1,537,990	23,740,531		1,321,969	19,388,861
Class R6	51,795,171	800,773,987		27,430,142	400,517,626
	159,115,984	$2,460,665,762		116,007,205	$1,690,056,585
Shares issued to shareholders in reinvestment of distributions
Class A	4,868,319	$75,561,883		3,614,742	$52,919,077
Class B	23,795	369,008		43,036	627,526
Class C	219,493	3,404,089		199,481	2,909,324
Class I	3,298,557	51,159,061		2,128,495	31,141,118
Class R1	9,985	154,844		10,116	147,754
Class R2	66,292	1,030,269		64,122	938,083
Class R3	368,554	5,720,729		339,081	4,961,707
Class R4	163,351	2,535,179		138,059	2,020,959
Class R6	3,816,106	59,121,160		2,566,377	37,541,301
	12,834,452	$199,056,222		9,103,509	$133,206,849

48

Notes to Financial Statements  - continued

	Year ended 4/30/21			Year ended 4/30/20
	Shares	Amount		Shares	Amount
Shares reacquired
Class A	(28,272,184)	$(435,990,316)		(26,968,583)	$(390,571,503)
Class B	(797,744)	(12,276,487)		(1,127,898)	(16,359,922)
Class C	(5,287,949)	(82,127,856)		(2,970,161)	(42,873,246)
Class I	(43,179,168)	(663,776,460)		(30,169,351)	(437,411,596)
Class R1	(176,156)	(2,712,449)		(184,794)	(2,680,016)
Class R2	(878,407)	(13,607,375)		(1,396,009)	(20,262,574)
Class R3	(3,759,359)	(58,152,935)		(3,953,802)	(56,911,619)
Class R4	(1,089,364)	(16,754,215)		(2,595,907)	(37,561,048)
Class R6	(18,193,954)	(279,071,842)		(19,012,314)	(273,966,448)
	(101,634,285)	$(1,564,469,935)		(88,378,819)	$(1,278,597,972)
Net change
Class A	20,231,325	$315,786,175		15,364,337	$227,756,107
Class B	(719,974)	(11,072,810)		(1,004,613)	(14,572,198)
Class C	(3,125,689)	(48,727,065)		(654,112)	(9,148,982)
Class I	16,512,691	258,411,841		14,487,425	210,796,628
Class R1	(43,928)	(683,757)		(43,091)	(621,126)
Class R2	(227,315)	(3,508,954)		(664,038)	(9,578,846)
Class R3	(340,259)	(5,298,181)		(602,339)	(7,907,372)
Class R4	611,977	9,521,495		(1,135,879)	(16,151,228)
Class R6	37,417,323	580,823,305		10,984,205	164,092,479
	70,316,151	$1,095,252,049		36,731,895	$544,665,462

Effective June 1, 2019, purchases of the fund’s Class B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

(6) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit of which $1 billion is reserved for use by the fund and certain other MFS U.S. funds. The line of credit is provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings,

49

Notes to Financial Statements  - continued

at rates equal to customary reference rates plus an agreed upon spread. For the year ended April 30, 2021, the fund’s commitment fee and interest expense were $26,734 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.

(7) Investments in Affiliated Issuers

An affiliated issuer may be considered one in which the fund owns 5% or more of the outstanding voting securities, or a company which is under common control. For the purposes of this report, the following were affiliated issuers:

Affiliated Issuers	Beginning Value	Purchases	Sales Proceeds	Realized Gain (Loss)	Change in Unrealized Appreciation or Depreciation	Ending Value
MFS Institutional Money Market Portfolio	$64,119,369	$1,956,511,374	$1,713,445,229	$(11,195)	$(4,510)	$307,169,809

    

Affiliated Issuers	Dividend Income	Capital Gain Distributions
MFS Institutional Money Market Portfolio	$237,468	$—

(8) Impacts of COVID-19

The pandemic related to the global spread of novel coronavirus disease (COVID-19), which was first detected in December 2019, has resulted in significant disruptions to global business activity and the global economy, as well as the economies of individual countries, the financial performance of individual companies and sectors, and the securities and commodities markets in general. Multiple surges in cases globally, the availability and widespread adoption of vaccines, and the emergence of variant strains of the virus continue to create uncertainty as to the future and long-term impacts resulting from the pandemic including impacts to the prices and liquidity of the fund's investments and the fund's performance.

50

Report of Independent Registered Public Accounting Firm

To the Board of Trustees of MFS Series Trust IX and the Shareholders of MFS Corporate Bond Fund:

Opinion on the Financial Statements and Financial Highlights

We have audited the accompanying statement of assets and liabilities of MFS Corporate Bond Fund (the “Fund”), including the portfolio of investments, as of April 30, 2021, the related statement of operations for the year then ended, the statements of changes in net assets for each of the two years in the period then ended, the financial highlights for each of the five years in the period then ended, and the related notes. In our opinion, the financial statements and financial highlights present fairly, in all material respects, the financial position of the Fund as of April 30, 2021, and the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period then ended, and the financial highlights for each of the five years in the period then ended, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements and financial highlights are the responsibility of the Fund’s management. Our responsibility is to express an opinion on the Fund's financial statements and financial highlights based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Fund in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements and financial highlights are free of material misstatement, whether due to error or fraud. The Fund is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Fund's internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements and financial highlights, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements and financial highlights. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements and financial highlights.

51

Report of Independent Registered Public Accounting Firm – continued

Our procedures included confirmation of securities owned as of April 30, 2021, by correspondence with the custodian and brokers; when replies were not received from brokers, we performed other auditing procedures. We believe that our audits provide a reasonable basis for our opinion.

DELOITTE & TOUCHE LLP

Boston, Massachusetts
June 15, 2021

We have served as the auditor of one or more of the MFS investment companies since 1924.

52

Trustees and Officers — Identification and Background

The Trustees and Officers of the Trust, as of June 1, 2021, are listed below, together with their principal occupations during the past five years. (Their titles may have varied during that period.) The address of each Trustee and Officer is 111 Huntington Avenue, Boston, Massachusetts 02199-7618.

Name, Age		Position(s) Held with Fund		Trustee/Officer Since(h)		Number of MFS Funds overseen by the Trustee		Principal Occupations During the Past Five Years		Other Directorships During the Past Five Years (j)
INTERESTED TRUSTEES
Robert J. Manning (k) (age 57)		Trustee		February 2004		135		Massachusetts Financial Services Company, Non-Executive Chairman (since January 2021); Director; Chairman of the Board; Executive Chairman (January 2017-2020); Co-Chief Executive Officer (2015-2016)		N/A
Michael W. Roberge (k) (age 54)		Trustee		January 2021		135		Massachusetts Financial Services Company, Chairman (since January 2021); Chief Executive Officer (since January 2017); Director; President (until December 2018); Chief Investment Officer (until December 2018); Co-Chief Executive Officer (until December 2016)		N/A
INDEPENDENT TRUSTEES
John P. Kavanaugh (age 66)		Trustee and Chair of Trustees		January 2009		135		Private investor		N/A
Steven E. Buller (age 69)		Trustee		February 2014		135		Private investor		N/A
John A. Caroselli (age 66)		Trustee		March 2017		135		Private investor; JC Global Advisors, LLC (management consulting), President (since 2015)		N/A
Maureen R. Goldfarb (age 66)		Trustee		January 2009		135		Private investor		N/A
Peter D. Jones (age 65)		Trustee		January 2019		135		Private investor		N/A

53

Trustees and Officers - continued

Name, Age		Position(s) Held with Fund		Trustee/Officer Since(h)		Number of MFS Funds overseen by the Trustee		Principal Occupations During the Past Five Years		Other Directorships During the Past Five Years (j)
James W. Kilman, Jr. (age 60)		Trustee		January 2019		135		Burford Capital Limited (finance and investment management), Senior Advisor (since May 3, 2021), Chief Financial Officer (2019 - May 2, 2021); KielStrand Capital LLC (family office), Chief Executive Officer (since 2016); Morgan Stanley & Co. (financial services), Vice Chairman of Investment Banking, Co-Head of Diversified Financials Coverage – Financial Institutions Investment Banking Group (until 2016)		Alpha-En Corporation, Director (2016-2019)
Clarence Otis, Jr. (age 65)		Trustee		March 2017		135		Private investor		VF Corporation, Director; Verizon Communications, Inc., Director; The Travelers Companies, Director
Maryanne L. Roepke (age 65)		Trustee		May 2014		135		Private investor		N/A
Laurie J. Thomsen (age 63)		Trustee		March 2005		135		Private investor		The Travelers Companies, Director; Dycom Industries, Inc., Director

    

Name, Age		Position(s) Held with Fund		Trustee/Officer Since(h)		Number of MFS Funds for which the Person is an Officer		Principal Occupations During the Past Five Years
OFFICERS
Christopher R. Bohane (k) (age 47)		Assistant Secretary and Assistant Clerk		July 2005		135		Massachusetts Financial Services Company, Senior Vice President and Associate General Counsel
Kino Clark (k) (age 52)		Assistant Treasurer		January 2012		135		Massachusetts Financial Services Company, Vice President

54

Trustees and Officers - continued

Name, Age		Position(s) Held with Fund		Trustee/Officer Since(h)		Number of MFS Funds for which the Person is an Officer		Principal Occupations During the Past Five Years
John W. Clark, Jr. (k) (age 54)		Assistant Treasurer		April 2017		135		Massachusetts Financial Services Company, Vice President (since March 2017); Deutsche Bank (financial services), Department Head - Treasurer's Office (until February 2017)
Thomas H. Connors (k) (age 61)		Assistant Secretary and Assistant Clerk		September 2012		135		Massachusetts Financial Services Company, Vice President and Senior Counsel
David L. DiLorenzo (k) (age 52)		President		July 2005		135		Massachusetts Financial Services Company, Senior Vice President
Heidi W. Hardin (k) (age 53)		Secretary and Clerk		April 2017		135		Massachusetts Financial Services Company, Executive Vice President and General Counsel (since March 2017); Harris Associates (investment management), General Counsel (until January 2017)
Brian E. Langenfeld (k) (age 48)		Assistant Secretary and Assistant Clerk		June 2006		135		Massachusetts Financial Services Company, Vice President and Senior Counsel
Amanda S. Mooradian (k) (age 42)		Assistant Secretary and Assistant Clerk		September 2018		135		Massachusetts Financial Services Company, Assistant Vice President and Senior Counsel
Susan A. Pereira (k) (age 50)		Assistant Secretary and Assistant Clerk		July 2005		135		Massachusetts Financial Services Company, Vice President and Assistant General Counsel
Kasey L. Phillips (k) (age 50)		Assistant Treasurer		September 2012		135		Massachusetts Financial Services Company, Vice President
Matthew A. Stowe (k) (age 46)		Assistant Secretary and Assistant Clerk		October 2014		135		Massachusetts Financial Services Company, Vice President and Assistant General Counsel
Martin J. Wolin (k) (age 53)		Chief Compliance Officer		July 2015		135		Massachusetts Financial Services Company, Senior Vice President and Chief Compliance Officer