UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number:

811-21457

Name of Fund:

BlackRock Allocation Target Shares

BATS: Series A Portfolio

BATS: Series C Portfolio

BATS: Series E Portfolio

BATS: Series M Portfolio

BATS: Series P Portfolio

BATS: Series S Portfolio

BATS: Series V Portfolio

Fund Address:  100 Bellevue Parkway, Wilmington, DE 19809

Name and address of agent for service: John M. Perlowski, Chief Executive Officer, BlackRock Allocation Target Shares, 50 Hudson Yards, New York, NY 10001

Registrant's telephone number, including area code:

(800) 441-7762

Date of fiscal year end:

03/31/2025

Date of reporting period:

03/31/2025

Item 1 — Reports to Stockholders

(a) The Reports to Shareholders are attached herewith

BATS: Series A Portfolio

BATAX

Annual Shareholder Report — March 31, 2025

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This annual shareholder report contains important information about BATS: Series A Portfolio (the “Fund”) for the period of April 1, 2024 to March 31, 2025. You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.

What were the Fund costs for the last year?

(based on a hypothetical $10,000 investment)

Fund name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
BATS: Series A Portfolio	$0(a)	0.01%

​(a)	Rounds to less than $1.

How did the Fund perform last year?

• For the reporting period ended March 31, 2025, the Fund returned 8.11%.
• For the same period, the Bloomberg U.S. Universal Index returned 5.24% and the Reference Benchmark returned 6.51%.

What contributed to performance?

All securitized asset classes contributed positively to the Fund’s performance. Contributions were led by exposure to non-agency residential mortgage-backed securities, particularly those backed by near prime, non-performing/re-performing and subprime loans. This was followed by holdings of single asset/single borrower senior tranches within commercial mortgage-backed securities and AAA-rated collateralized loan obligations (“CLOs”), as those categories posted the largest gains over the period. Allocations to AA-rated CLOs, private student loan asset-backed securities (“ABS”) and unsecured consumer ABS also showed positive returns.

The Fund held some private whole loan securities including commercial mortgage loans and consumer whole loans. These private holdings also produced positive returns.

What detracted from performance?

There were no material detractors from the Fund’s performance during the reporting period.

The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.

Fund performance

Cumulative performance: September 21, 2015 through March 31, 2025

Initial investment of $10,000

See “Average annual total returns” for additional information on fund performance.

Average annual total returns

	1 Year		5 Years		Since Fund Inception
BATS: Series A Portfolio	8.11	%	5.79	%	4.70	%
Bloomberg U.S. Universal Index	5.24		0.32		2.02
Reference Benchmark	6.51		2.27		2.48

Key Fund statistics

Net Assets	$3,576,385,769
Number of Portfolio Holdings	1,753
Net Investment Advisory Fees	$0
Portfolio Turnover Rate	50%

The Fund commenced operations on September 21, 2015.

Reference Benchmark is a customized weighted index comprised of the returns of the Bloomberg U.S. Asset-Backed Securities Index (50%)/Bloomberg Non-Agency Investment Grade CMBS Index (50%).

Past performance is not an indication of future results. Performance results may include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles. Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. Visit blackrock.com for more recent performance information.

What did the Fund invest in?

(as of March 31, 2025)

Portfolio composition

Investment Type	Percent of Total Investments(a)
Non-Agency Mortgage-Backed Securities	50.0	%
Asset-Backed Securities	49.3	%
U.S. Government Sponsored Agency Securities	0.4	%
Floating Rate Loan Interests	0.3	%
Corporate Bonds	—	%(b)

Credit quality allocation

Credit Rating(c)	Percent of Total Investments(a)
AAA/Aaa(d)	36.5	%
AA/Aa	5.2	%
A	2.8	%
BBB/Baa	2.9	%
BB/Ba	3.4	%
B	0.8	%
CCC/Caa	1.7	%
CC/Ca	1.2	%
C	0.9	%
D	0.1	%
N/R	44.5	%

​(a)	Excludes short-term securities, short investments and options, if any.
​(b)	Rounds to less than 0.1%.
​(c)	For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.
​(d)	The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuers. Using this approach, the investment adviser has deemed unrated U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations to be of similar credit quality as investments rated AAA/Aaa.

Additional information

If you wish to view additional information about the Fund, including but not limited to financial statements, the Fund’s prospectus, and proxy voting policies and procedures, please visit blackrock.com/fundreports. For proxy voting records, visit blackrock.com/proxyrecords.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Fund at (800) 441-7762.

The Fund is not sponsored, endorsed, issued, sold, or promoted by Bloomberg Index Services Limited and its affiliates, nor does this company make any representation regarding the advisability of investing in the Fund. BlackRock is not affiliated with the company listed above.

©2025 BlackRock, Inc. or its affiliates. All rights reserved. BLACKROCK is a registered trademark of BlackRock, Inc. or its affiliates. All other trademarks are those of their respective owners.

BATS: Series A Portfolio

Annual Shareholder Report — March 31, 2025

BATAX-03/25-AR

BATS: Series C Portfolio

BRACX

Annual Shareholder Report — March 31, 2025

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This annual shareholder report contains important information about BATS: Series C Portfolio (the “Fund”) for the period of April 1, 2024 to March 31, 2025. You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.

What were the Fund costs for the last year?

(based on a hypothetical $10,000 investment)

Fund name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
BATS: Series C Portfolio	$0(a)	0.00%(b)

​(a)	Rounds to less than $1.
​(b)	Rounds to less than 0.01%.

How did the Fund perform last year?

• For the reporting period ended March 31, 2025, the Fund returned 4.73%.
• For the same period, the Bloomberg U.S. Aggregate Bond Index returned 4.88% and the Bloomberg U.S. Credit Index returned 4.87%.

What contributed to performance?

The Fund’s allocations to the banking, utilities and technology sectors were the leading contributors.

What detracted from performance?

The Fund’s duration and yield curve positioning was the largest detractor, followed by allocations to the consumer services sector and non-U.S. government debt. (Duration is a measure of interest rate sensitivity).

The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.

Fund performance

Cumulative performance: April 1, 2015 through March 31, 2025

Initial investment of $10,000

See “Average annual total returns” for additional information on fund performance.

Average annual total returns

	1 Year		5 Years		10 Years
BATS: Series C Portfolio	4.73	%	1.78	%	2.68	%
Bloomberg U.S. Aggregate Bond Index	4.88		(0.40	)	1.46
Bloomberg U.S. Credit Index	4.87		1.35		2.31

Key Fund statistics

Net Assets	$439,499,546
Number of Portfolio Holdings	837
Net Investment Advisory Fees	$0
Portfolio Turnover Rate	446%

The Fund has added the Bloomberg U.S. Aggregate Bond Index in response to new regulatory requirements.

Past performance is not an indication of future results. Performance results may include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles. Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. Visit blackrock.com for more recent performance information.

What did the Fund invest in?

(as of March 31, 2025)

Portfolio composition

Investment Type	Percent of Total Investments(a)
Corporate Bonds	88.9	%
Preferred Securities	3.3	%
U.S. Treasury Obligations	3.0	%
Foreign Government Obligations	3.0	%
Foreign Agency Obligations	0.9	%
Municipal Bonds	0.9	%

Credit quality allocation

Credit Rating(b)	Percent of Total Investments(a)
AAA/Aaa(c)	3.0	%
AA/Aa	5.4	%
A	27.0	%
BBB/Baa	61.1	%
BB/Ba	2.3	%
N/R	1.2	%

​(a)	Excludes short-term securities, short investments and options, if any.
​(b)	For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.
​(c)	The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuers. Using this approach, the investment adviser has deemed unrated U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations to be of similar credit quality as investments rated AAA/Aaa.

Additional information

If you wish to view additional information about the Fund, including but not limited to financial statements, the Fund’s prospectus, and proxy voting policies and procedures, please visit blackrock.com/fundreports. For proxy voting records, visit blackrock.com/proxyrecords.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Fund at (800) 441-7762.

The Fund is not sponsored, endorsed, issued, sold, or promoted by Bloomberg Index Services Limited and its affiliates, nor does this company make any representation regarding the advisability of investing in the Fund. BlackRock is not affiliated with the company listed above.

©2025 BlackRock, Inc. or its affiliates. All rights reserved. BLACKROCK is a registered trademark of BlackRock, Inc. or its affiliates. All other trademarks are those of their respective owners.

BATS: Series C Portfolio

Annual Shareholder Report — March 31, 2025

BRACX-03/25-AR

BATS: Series E Portfolio

BATEX

Annual Shareholder Report — March 31, 2025

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This annual shareholder report contains important information about BATS: Series E Portfolio (the “Fund”) for the period of April 1, 2024 to March 31, 2025. You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.

What were the Fund costs for the last year?

(based on a hypothetical $10,000 investment)

Fund name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
BATS: Series E Portfolio	$0(a)	0.05%

​(a)	Rounds to less than $1.

How did the Fund perform last year?

• For the reporting period ended March 31, 2025, the Fund returned 5.05%.
• For the same period, the Bloomberg Municipal Bond Index returned 1.22% and the Bloomberg Municipal High Yield Bond Index returned 5.59%.

What contributed to performance?

On a sector basis, other industries, utilities and healthcare were the largest contributors to absolute performance. In terms of ratings categories, non-rated bonds—which had a 41% portfolio weighting at the close of the period—were the largest contributors by a wide margin. More generally, high yield bonds outperformed investment-grade securities. Bonds with maturities of 25 years and longer were also significant contributors.

At the individual holding level, the Fund benefitted from strong total returns for Puerto Rico Electric Power Authority bonds, Puerto Rico contingent value securities, and the bonds of Brightline East and Brightline West (which were issued to finance a high-speed rail project between Las Vegas and Southern California).

What detracted from performance?

At a time of positive performance for the Fund, no sector, rating, maturity, or coupon category experienced a negative total return. A few individual tobacco bonds posted losses due to declining consumption figures, but the Fund’s overall position in the sector nonetheless delivered a gain. Short-duration, high-grade securities, while producing gains in absolute terms, made the smallest contribution.

The Fund’s cash weighting was slightly elevated as of March 31, 2025. Cash yields remained attractive, and the securities provided stability to the Fund in periods of volatility.

The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.

Fund performance

Cumulative performance: April 1, 2015 through March 31, 2025

Initial investment of $10,000

See “Average annual total returns” for additional information on fund performance.

Average annual total returns

	1 Year		5 Years		10 Years
BATS: Series E Portfolio	5.05	%	4.19	%	4.47	%
Bloomberg Municipal Bond Index	1.22		1.07		2.13
Bloomberg Municipal High Yield Bond Index	5.59		4.31		4.25
Customized Reference Benchmark	4.05		3.31		N/A
Customized Reference Benchmark (prior)	2.73		2.21		N/A

Key Fund statistics

Net Assets	$527,280,263
Number of Portfolio Holdings	655
Net Investment Advisory Fees	$0
Portfolio Turnover Rate	23%

The Fund has added the Bloomberg Municipal Bond Index in response to new regulatory requirements.

Beginning July 29, 2024, the Fund started to compare its performance to that of the Customized Reference Benchmark comprised of 60% Bloomberg Municipal Bond: High Yield (non-Investment Grade) Total Return Index, 20% Bloomberg Municipal Bond Rated Baa Index, and 20% Bloomberg Municipal Investment Grade ex BBB. Fund management believes that the new benchmark is more representative of the types of investments held within the Fund. The Customized Reference Benchmark commenced on September 30, 2016.

Prior to July 29, 2024, the Fund compared its performance to that of the prior Customized Reference Benchmark, which is comprised of the Bloomberg Municipal Bond Index Total Return Index Value Unhedged (65%) and the Bloomberg Municipal Bond: High Yield (non-Investment Grade) Total Return Index (35%). The prior Customized Reference Benchmark commenced on September 30, 2016.

Past performance is not an indication of future results. Performance results may include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles. Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. Visit blackrock.com for more recent performance information.

What did the Fund invest in?

(as of March 31, 2025)

Sector allocation

Sector	Percent of Total Investments
County/City/Special District/School District	35.9	%
Transportation	17.0	%
Utilities	14.7	%
Health Care	11.3	%
Education	10.6	%
Housing	5.9	%
Tobacco	4.6	%

Credit quality allocation

Credit Rating(a)	Percent of Total Investments
AAA/Aaa	2.8	%
AA/Aa	16.7	%
A	11.8	%
BBB/Baa	10.5	%
BB/Ba	7.9	%
B	1.5	%
CCC/Caa	0.3	%
N/R	48.5	%

​(a)

For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.

Additional information

If you wish to view additional information about the Fund, including but not limited to financial statements, the Fund’s prospectus, and proxy voting policies and procedures, please visit blackrock.com/fundreports. For proxy voting records, visit blackrock.com/proxyrecords.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Fund at (800) 441-7762.

The Fund is not sponsored, endorsed, issued, sold, or promoted by Bloomberg Index Services Limited and its affiliates, nor does this company make any representation regarding the advisability of investing in the Fund. BlackRock is not affiliated with the company listed above.

©2025 BlackRock, Inc. or its affiliates. All rights reserved. BLACKROCK is a registered trademark of BlackRock, Inc. or its affiliates. All other trademarks are those of their respective owners.

BATS: Series E Portfolio

Annual Shareholder Report — March 31, 2025

BATEX-03/25-AR

BATS: Series M Portfolio

BRAMX

Annual Shareholder Report — March 31, 2025

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This annual shareholder report contains important information about BATS: Series M Portfolio (the “Fund”) for the period of April 1, 2024 to March 31, 2025. You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.

What were the Fund costs for the last year?

(based on a hypothetical $10,000 investment)

Fund name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
BATS: Series M Portfolio	$0(a)	0.00%(b)

​(a)	Rounds to less than $1.
​(b)	Rounds to less than 0.01%.

How did the Fund perform last year?

• For the reporting period ended March 31, 2025, the Fund returned 5.96%.
• For the same period, the Bloomberg U.S. Aggregate Bond Index returned 4.88% and the Bloomberg MBS Index returned 5.39%.

What contributed to performance?

Out-of-benchmark allocations to commercial mortgage-backed securities were a leading contributor to performance. Agency mortgage derivatives and fixed rate collateralized mortgage obligations also contributed positively. Within residential mortgage-backed securities, the Fund’s active benchmark strategy, which implements relative value decisions between specified pools and to-be-announced securities (“TBAs”) contributed positively to performance.

What detracted from performance?

The Fund’s active management of duration and corresponding sensitivity to changes in interest rates detracted modestly from performance over the period.

The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.

Fund performance

Cumulative performance: April 1, 2015 through March 31, 2025

Initial investment of $10,000

See “Average annual total returns” for additional information on fund performance.

Average annual total returns

	1 Year		5 Years		10 Years
BATS: Series M Portfolio	5.96	%	0.13	%	1.51	%
Bloomberg U.S. Aggregate Bond Index	4.88		(0.40	)	1.46
Bloomberg MBS Index	5.39		(0.69	)	1.11

Key Fund statistics

Net Assets	$1,295,016,533
Number of Portfolio Holdings	1,145
Net Investment Advisory Fees	$0
Portfolio Turnover Rate	892%

The Fund has added the Bloomberg U.S. Aggregate Bond Index in response to new regulatory requirements.

Past performance is not an indication of future results. Performance results may include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles. Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. Visit blackrock.com for more recent performance information.

What did the Fund invest in?

(as of March 31, 2025)

Portfolio composition

Investment Type	Percent of Total Investments(a)
U.S. Government Sponsored Agency Securities	93.1	%
Non-Agency Mortgage-Backed Securities	5.4	%
Asset-Backed Securities	1.5	%

Credit quality allocation

Credit Rating(b)	Percent of Total Investments(a)
AAA/Aaa(c)	97.3	%
AA/Aa	0.2	%
A	0.2	%
BBB/Baa	0.1	%
N/R	2.2	%

​(a)	Excludes short-term securities, short investments and options, if any.
​(b)	For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.
​(c)	The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuers. Using this approach, the investment adviser has deemed unrated U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations to be of similar credit quality as investments rated AAA/Aaa.

Additional information

If you wish to view additional information about the Fund, including but not limited to financial statements, the Fund’s prospectus, and proxy voting policies and procedures, please visit blackrock.com/fundreports. For proxy voting records, visit blackrock.com/proxyrecords.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Fund at (800) 441-7762.

The Fund is not sponsored, endorsed, issued, sold, or promoted by Bloomberg Index Services Limited and its affiliates, nor does this company make any representation regarding the advisability of investing in the Fund. BlackRock is not affiliated with the company listed above.

©2025 BlackRock, Inc. or its affiliates. All rights reserved. BLACKROCK is a registered trademark of BlackRock, Inc. or its affiliates. All other trademarks are those of their respective owners.

BATS: Series M Portfolio

Annual Shareholder Report — March 31, 2025

BRAMX-03/25-AR

BATS: Series P Portfolio

BATPX

Annual Shareholder Report — March 31, 2025

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This annual shareholder report contains important information about BATS: Series P Portfolio (the “Fund”) for the period of April 1, 2024 to March 31, 2025. You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.

What were the Fund costs for the last year?

(based on a hypothetical $10,000 investment)

Fund name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
BATS: Series P Portfolio	$0(a)	0.00%(b)

​(a)	Rounds to less than $1.
​(b)	Rounds to less than 0.01%.

How did the Fund perform last year?

• For the reporting period ended March 31, 2025, the Fund returned 6.75%.
• For the same period, the Bloomberg U.S. Aggregate Bond Index returned 4.88% and the Bloomberg U.S. Treasury 7-10 Year Bond Index returned 4.65%.

What contributed to performance?

Allocations to cash and cash-like securities made the largest contribution to Fund performance. The Fund held cash as collateral in conjunction with its investments in U.S. Treasury futures and interest rate swaps.

The use and cost of derivatives will result in a negative contribution to returns when interest rates fall; however, the Fund’s strategy is designed to offset these costs by holding shares of BlackRock Allocation Target Shares: Series S Portfolio (“Series S Portfolio”), a short-term proprietary fund. The use of derivatives is necessary to achieve the Fund’s objective and should therefore be evaluated in a portfolio context and not as a standalone strategy. The Fund’s use of derivatives contributed to results.

The Fund’s position in the Series S Portfolio also contributed positively.

What detracted from performance?

At a time of positive performance for the Fund, no aspects of its positioning stood out as meaningful detractors. However, certain individual securities in BlackRock Allocation Target Shares Series S posted negative absolute returns during the reporting period.

The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.

Fund performance

Cumulative performance: April 1, 2015 through March 31, 2025

Initial investment of $10,000

See “Average annual total returns” for additional information on fund performance.

Average annual total returns

	1 Year		5 Years		10 Years
BATS: Series P Portfolio	6.75	%	8.17	%	2.56	%
Bloomberg U.S. Aggregate Bond Index	4.88		(0.40	)	1.46
Bloomberg U.S. Treasury 7-10 Year Bond Index	4.65		(2.52	)	0.87
Bloomberg U.S. Bellwether 10 Year Swap Index	4.24		(3.37	)	0.68

Key Fund statistics

Net Assets	$3,481,645
Number of Portfolio Holdings	16
Net Investment Advisory Fees	$0
Portfolio Turnover Rate	134%

The Fund has added the Bloomberg U.S. Aggregate Bond Index in response to new regulatory requirements.

The Fund's 1 Year annual total return was impacted by a third-party payment for an operating event. Excluding the payment, the Fund's 1 Year annual total return would have been 6.34%.

Past performance is not an indication of future results. Performance results may include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles. Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. Visit blackrock.com for more recent performance information.

What did the Fund invest in?

(as of March 31, 2025)

Portfolio composition

Investment Type	Percent of Total Investments
Fixed-Income Funds	21.0	%
Short-Term Securities	79.0	%

Additional information

If you wish to view additional information about the Fund, including but not limited to financial statements, the Fund’s prospectus, and proxy voting policies and procedures, please visit blackrock.com/fundreports. For proxy voting records, visit blackrock.com/proxyrecords.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Fund at (800) 441-7762.

The Fund is not sponsored, endorsed, issued, sold, or promoted by Bloomberg Index Services Limited and its affiliates, nor does this company make any representation regarding the advisability of investing in the Fund. BlackRock is not affiliated with the company listed above.

©2025 BlackRock, Inc. or its affiliates. All rights reserved. BLACKROCK is a registered trademark of BlackRock, Inc. or its affiliates. All other trademarks are those of their respective owners.

BATS: Series P Portfolio

Annual Shareholder Report — March 31, 2025

BATPX-03/25-AR

BATS: Series S Portfolio

BRASX

Annual Shareholder Report — March 31, 2025

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This annual shareholder report contains important information about BATS: Series S Portfolio (the “Fund”) for the period of April 1, 2024 to March 31, 2025. You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.

What were the Fund costs for the last year?

(based on a hypothetical $10,000 investment)

Fund name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
BATS: Series S Portfolio	$0(a)	0.00%(b)

​(a)	Rounds to less than $1.
​(b)	Rounds to less than 0.01%.

How did the Fund perform last year?

• For the reporting period ended March 31, 2025, the Fund returned 6.31%.
• For the same period, the Bloomberg U.S. Aggregate Bond Index returned 4.88% and the ICE BofA 1-3 Year U.S. Treasury Index returned 5.43%.

What contributed to performance?

The Fund’s allocation to investment-grade corporate bonds made the largest contribution to absolute performance. Allocations to asset-backed securities, U.S. Treasuries, agency residential mortgage-backed securities, and commercial mortgage-backed securities positively impacted returns, as well.

What detracted from performance?

At a time of positive performance for the Fund, no aspects of its positioning stood out as meaningful detractors. However, certain individual securities posted negative absolute returns in the period.

The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.

Fund performance

Cumulative performance: April 1, 2015 through March 31, 2025

Initial investment of $10,000

See “Average annual total returns” for additional information on fund performance.

Average annual total returns

	1 Year		5 Years		10 Years
BATS: Series S Portfolio	6.31	%	3.26	%	2.62	%
Bloomberg U.S. Aggregate Bond Index	4.88		(0.40	)	1.46
ICE BofA 1-3 Year U.S. Treasury Index	5.43		1.16		1.50

Key Fund statistics

Net Assets	$364,929,043
Number of Portfolio Holdings	666
Net Investment Advisory Fees	$0
Portfolio Turnover Rate	162%

The Fund has added the Bloomberg U.S. Aggregate Bond Index in response to new regulatory requirements.

An index that is a subset of ICE BofA US Treasury Index including all securities with a remaining term to final maturity less than 3 years. On December 1, 2023, the Fund began to compare its performance to the standard pricing time of the ICE BofA 1-3 Year U.S. Treasury Index (the “Index”). Index data prior to March 1, 2021 is for the Index’s standard pricing time of 3pm. Index data from March 1, 2021 through November 30, 2023 is for a custom 4pm pricing variant of the Index. Index returns beginning on December 1, 2023 reflect the Index’s new standard pricing time of 4pm. The change of the Index’s standard pricing time from 3pm to 4pm resulted in the discontinuation of the custom 4pm pricing variant used from March 1, 2021 through November 30, 2023.

Past performance is not an indication of future results. Performance results may include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles. Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. Visit blackrock.com for more recent performance information.

What did the Fund invest in?

(as of March 31, 2025)

Portfolio composition

Investment Type	Percent of Total Investments(a)
Corporate Bonds	33.5	%
Asset-Backed Securities	24.0	%
U.S. Treasury Obligations	16.9	%
Non-Agency Mortgage-Backed Securities	14.2	%
U.S. Government Sponsored Agency Securities	11.0	%
Foreign Government Obligations	0.4	%

Credit quality allocation

Credit Rating(b)	Percent of Total Investments
AAA/Aaa(c)	61.4	%
AA/Aa	1.7	%
A	12.9	%
BBB/Baa	19.0	%
N/R	5.0	%

​(a)	Excludes short-term securities, short investments and options, if any.
​(b)	For purposes of this report, credit quality ratings shown above reflect the highest rating assigned by either S&P Global Ratings or Moody’s Investors Service, Inc. if ratings differ. These rating agencies are independent, nationally recognized statistical rating organizations and are widely used. Investment grade ratings are credit ratings of BBB/Baa or higher. Below investment grade ratings are credit ratings of BB/Ba or lower. Investments designated N/R are not rated by either rating agency. Unrated investments do not necessarily indicate low credit quality. Credit quality ratings are subject to change.
​(c)	The investment adviser evaluates the credit quality of unrated investments based upon certain factors including, but not limited to, credit ratings for similar investments and financial analysis of sectors, individual investments and/or issuers. Using this approach, the investment adviser has deemed unrated U.S. Government Sponsored Agency Securities and U.S. Treasury Obligations to be of similar credit quality as investments rated AAA/Aaa.

Additional information

If you wish to view additional information about the Fund, including but not limited to financial statements, the Fund’s prospectus, and proxy voting policies and procedures, please visit blackrock.com/fundreports. For proxy voting records, visit blackrock.com/proxyrecords.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Fund at (800) 441-7762.

The Fund is not sponsored, endorsed, issued, sold, or promoted by Bloomberg Index Services Limited, ICE Data Indices, LLC, and their respective affiliates, nor do these companies make any representation regarding the advisability of investing in the Fund. BlackRock is not affiliated with the companies listed above.

©2025 BlackRock, Inc. or its affiliates. All rights reserved. BLACKROCK is a registered trademark of BlackRock, Inc. or its affiliates. All other trademarks are those of their respective owners.

BATS: Series S Portfolio

Annual Shareholder Report — March 31, 2025

BRASX-03/25-AR

BATS: Series V Portfolio

BATVX

Annual Shareholder Report — March 31, 2025

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This annual shareholder report contains important information about BATS: Series V Portfolio (the “Fund”) for the period of April 1, 2024 to March 31, 2025. You can find additional information about the Fund at blackrock.com/fundreports. You can also request this information by contacting us at (800) 441‑7762.

What were the Fund costs for the last year?

(based on a hypothetical $10,000 investment)

Fund name	Costs of a $10,000 investment	Costs paid as a percentage of a $10,000 investment
BATS: Series V Portfolio	$0(a)	0.00%(b)

​(a)	Rounds to less than $1.
​(b)	Rounds to less than 0.01%.

How did the Fund perform last year?

• For the reporting period ended March 31, 2025, the Fund returned 3.23%.
• For the same period, the Bloomberg Municipal Bond Index returned 1.22% and the SIFMA Municipal Swap Index returned 3.21%.

What contributed to performance?

The Fund maintained high levels of liquidity while providing an attractive yield primarily through its holdings of variable rate demand notes (“VRDNs”). The Fund also opportunistically laddered maturities in holdings of attractive municipal commercial paper and select fixed-rate, tax-backed local credits, through both municipal notes and bonds. The Fund maintained its bias for daily and weekly reset VRDNs while also holding select longer-dated commercial paper and municipal notes. The Fund’s weighted average maturity (“WAM”) of 29 days remained longer than the benchmark WAM of 7 days, as the Fund took advantage of opportunities presented by interest rate volatility to purchase fixed-rate securities when their yields appeared attractive relative to expected VRDN yields.

What detracted from performance?

There were no material detractors from the Fund’s performance during the reporting period.

The views expressed reflect the opinions of BlackRock as of the date of this report and are subject to change based on changes in market, economic or other conditions. These views are not intended to be a forecast of future events and are no guarantee of future results.

Fund performance

Cumulative performance: May 5, 2021 through March 31, 2025

Initial investment of $10,000

See “Average annual total returns” for additional information on fund performance.

Average annual total returns

	1 Year		Since Fund Inception
BATS: Series V Portfolio	3.23	%	2.17	%
Bloomberg Municipal Bond Index	1.22		(0.24	)
SIFMA Municipal Swap Index	3.21		2.19

Key Fund statistics

Net Assets	$125,127,991
Number of Portfolio Holdings	81
Net Investment Advisory Fees	$0
Portfolio Turnover Rate	233%

The Fund commenced operations on May 5, 2021.

The Fund has added the Bloomberg Municipal Bond Index in response to new regulatory requirements.

Past performance is not an indication of future results. Performance results may include adjustments made for financial reporting purposes in accordance with U.S. generally accepted accounting principles. Performance results do not reflect the deduction of taxes that a shareholder would pay on fund distributions or on the redemption or sale of fund shares. Visit blackrock.com for more recent performance information.

What did the Fund invest in?

(as of March 31, 2025)

Sector allocation

Sector	Percent of Total Investments
Housing	26.5	%
County/City/Special District/School District	25.1	%
Health Care	19.3	%
Education	15.8	%
Utilities	12.5	%
Transportation	0.8	%

Additional information

If you wish to view additional information about the Fund, including but not limited to financial statements, the Fund’s prospectus, and proxy voting policies and procedures, please visit blackrock.com/fundreports. For proxy voting records, visit blackrock.com/proxyrecords.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Fund at (800) 441-7762.

The Fund is not sponsored, endorsed, issued, sold, or promoted by Bloomberg Index Services Limited and its affiliates, nor does this company make any representation regarding the advisability of investing in the Fund. BlackRock is not affiliated with the company listed above.

©2025 BlackRock, Inc. or its affiliates. All rights reserved. BLACKROCK is a registered trademark of BlackRock, Inc. or its affiliates.

BATS: Series V Portfolio

Annual Shareholder Report — March 31, 2025

BATVX-03/25-AR

(b) Not Applicable

Lorenzo A. Flores

Catherine A. Lynch

Arthur P. Steinmetz

Under applicable securities laws, a person determined to be an audit committee financial expert will not be deemed an “expert” for any purpose, including without limitation for the purposes of Section 11 of the Securities Act of 1933, as a result of being designated or identified as an audit committee financial expert. The designation or identification of a person as an audit committee financial expert does not impose on such person any duties, obligations, or liabilities greater than the duties, obligations, and liabilities imposed on such person as a member of the audit committee and board of trustees in the absence of such designation or identification. The designation or identification of a person as an audit committee financial expert does not affect the duties, obligations, or liability of any other member of the audit committee or board of trustees.

The following table presents fees billed by Deloitte & Touche LLP (“D&T”) in each of the last two fiscal years for the services rendered to the Fund:

The following table presents fees billed by D&T that were required to be approved by the registrant’s audit committee (the “Committee”) for services that relate directly to the operations or financial reporting of the Fund and that are rendered on behalf of BlackRock Advisors, LLC (the “Investment Adviser” or “BlackRock”) and entities controlling, controlled by, or under common control with BlackRock (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser) that provide ongoing services to the Fund (“Affiliated Service Providers”):

2

¹ The nature of the services includes assurance and related services reasonably related to the performance of the audit or review of financial statements not included in Audit Fees, including accounting consultations, agreed-upon procedure reports, attestation reports, comfort letters, out-of-pocket expenses and internal control reviews not required by regulators.

² The nature of the services includes tax compliance and/or tax preparation, including services relating to the filing or amendment of federal, state or local income tax returns, regulated investment company qualification reviews, taxable income and tax distribution calculations.

³ Non-audit fees of $2,149,000 and $2,149,000 for the current fiscal year and previous fiscal year, respectively, were paid to the Fund’s principal accountant in their entirety by BlackRock, in connection with services provided to the Affiliated Service Providers of the Fund and of certain other funds sponsored and advised by BlackRock or its affiliates for a service organization review and an accounting research tool subscription. These amounts represent aggregate fees paid by BlackRock and were not allocated on a per fund basis.

(e)(1) Audit Committee Pre-Approval Policies and Procedures:

The Committee has adopted policies and procedures with regard to the pre-approval of services. Audit, audit-related and tax compliance services provided to the registrant on an annual basis require specific pre-approval by the Committee. The Committee also must approve other non-audit services provided to the registrant and those non-audit services provided to the Investment Adviser and Affiliated Service Providers that relate directly to the operations and the financial reporting of the registrant. Certain of these non-audit services that the Committee believes are (a) consistent with the SEC’s auditor independence rules and (b) routine and recurring services that will not impair the independence of the independent accountants may be approved by the Committee without consideration on a specific case-by-case basis (“general pre-approval”). The term of any general pre-approval is 12 months from the date of the pre-approval, unless the Committee provides for a different period. Tax or other non-audit services provided to the registrant which have a direct impact on the operations or financial reporting of the registrant will only be deemed pre-approved provided that any individual project does not exceed $10,000 attributable to the registrant or $50,000 per project. For this purpose, multiple projects will be aggregated to determine if they exceed the previously mentioned cost levels.

Any proposed services exceeding the pre-approved cost levels will require specific pre-approval by the Committee, as will any other services not subject to general pre-approval (e.g., unanticipated but permissible services). The Committee is informed of each service approved subject to general pre-approval at the next regularly scheduled in-person board meeting. At this meeting, an analysis of such services is presented to the Committee for ratification. The Committee may delegate to the Committee Chairman the authority to approve the provision of and fees for any specific engagement of permitted non-audit services, including services exceeding pre-approved cost levels.

(e)(2) None of the services described in each of Items 4(b) through (d) were approved by the Committee pursuant to the de minimis exception in paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X.

(f) Not Applicable

(g) The aggregate non-audit fees, defined as the sum of the fees shown under “Audit-Related Fees,” “Tax Fees” and “All Other Fees,” paid to the accountant for services rendered by the accountant to the registrant, the Investment Adviser and the Affiliated Service Providers were:

3

Additionally, the amounts billed by D&T in connection with services provided to the Affiliated Service Providers of the Fund and of other funds sponsored or advised by BlackRock or its affiliates during the current and previous fiscal years for a service organization review and an accounting research tool subscription were:

These amounts represent aggregate fees paid by BlackRock and were not allocated on a per fund basis.

(h) The Committee has considered and determined that the provision of non-audit services that were rendered to the Investment Adviser and the Affiliated Service Providers that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant’s independence.

(i) – Not Applicable

(j) – Not Applicable

(a) The registrant’s Schedule of Investments is included as part of the Financial Statement and Financial Highlights for Open-End Management Investment Companies filed under Item 7 of this Form.

(b) Not Applicable due to no such divestments during the semi-annual period covered since the previous Form N-CSR filing.

(a) The registrant’s Financial Statements are attached herewith.

(b) The registrant’s Financial Highlights are attached herewith.

BlackRock Allocation Target Shares

Table of Contents

The Benefits and Risks of Leveraging

The Funds may utilize leverage to seek to enhance returns and net asset value (“NAV”). However, there is no guarantee that these objectives can be achieved in all interest rate environments.

Series E Portfolio may leverage its assets through the use of proceeds received in tender option bond (“TOB”) transactions, as described in the Notes to Financial Statements. In a TOB Trust transaction, the Fund transfers municipal bonds or other municipal securities into a special purpose entity (a “TOB Trust”). TOB investments generally provide the Fund with economic benefits in periods of declining short-term interest rates but expose the Fund to risks during periods of rising short-term interest rates. Additionally, fluctuations in the market value of municipal bonds deposited into a TOB Trust may adversely affect the Fund’s NAV per share.

In general, the concept of leveraging is based on the premise that the financing cost of leverage, which is based on short-term interest rates, is normally lower than the income earned by each Fund on its longer-term portfolio investments purchased with the proceeds from leverage. To the extent that the total assets of each Fund (including the assets obtained from leverage) are invested in higher-yielding portfolio investments, each Fund’s shareholders benefit from the incremental net income.

The interest earned on securities purchased with the proceeds from leverage is distributed to each Fund’s shareholders, and the value of these portfolio holdings is reflected in each Fund’s per share NAV. However, in order to benefit shareholders, the return on assets purchased with leverage proceeds must exceed the ongoing costs associated with the leverage. If interest and other ongoing costs of leverage exceed a Fund’s return on assets purchased with leverage proceeds, income to shareholders is lower than if the Funds had not used leverage.

Furthermore, the value of each Fund’s portfolio investments generally varies inversely with the direction of long-term interest rates, although other factors can also influence the value of portfolio investments. As a result, changes in interest rates can influence each Fund’s NAV positively or negatively in addition to the impact on each Fund’s performance from leverage. Changes in the direction of interest rates are difficult to predict accurately, and there is no assurance that a Fund’s leveraging strategy will be successful.

The use of leverage also generally causes greater changes in each Fund’s NAV and dividend rates than comparable portfolios without leverage. In a declining market, leverage is likely to cause a greater decline in the NAV of a Fund’s shares than if the Fund were not leveraged. In addition, each Fund may be required to sell portfolio securities at inopportune times or at distressed values in order to comply with regulatory requirements applicable to the use of leverage or as required by the terms of the leverage instruments, which may cause the Funds to incur losses. The use of leverage may limit a Fund’s ability to invest in certain types of securities or use certain types of hedging strategies. Each Fund incurs expenses in connection with the use of leverage, all of which are borne by each Fund’s shareholders and may reduce income.

Derivative Financial Instruments

The Funds may invest in various derivative financial instruments. These instruments are used to obtain exposure to a security, commodity, index, market, and/or other assets without owning or taking physical custody of securities, commodities and/or other referenced assets or to manage market, equity, credit, interest rate, foreign currency exchange rate, commodity and/or other risks. Derivative financial instruments may give rise to a form of economic leverage and involve risks, including the imperfect correlation between the value of a derivative financial instrument and the underlying asset, possible default of the counterparty to the transaction or illiquidity of the instrument. Pursuant to Rule 18f-4 under the 1940 Act, among other things, the Funds must either use derivative financial instruments with embedded leverage in a limited manner or comply with an outer limit on fund leverage risk based on value-at-risk. The Funds’ successful use of a derivative financial instrument depends on the investment adviser’s ability to predict pertinent market movements accurately, which cannot be assured. The use of these instruments may result in losses greater than if they had not been used, may limit the amount of appreciation a Fund can realize on an investment and/or may result in lower distributions paid to shareholders. The Funds’ investments in these instruments, if any, are discussed in detail in the Notes to Financial Statements.