N-2 - $ / shares

6 Months Ended

Jun. 30, 2025

Dec. 31, 2024

Cover [Abstract]

Entity Central Index Key

0001160864

Amendment Flag

false

Document Type

N-CSRS

Entity Registrant Name

BlackRock Core Bond Trust

General Description of Registrant [Abstract]

Investment Objectives and Practices [Text Block]

Investment Objective

BlackRock Core Bond Trust’s (BHK) (the “Trust”) investment objective is to provide current income and capital appreciation. The Trust seeks to achieve its investment objective by investing, under normal market conditions, at least 75% of its managed assets in bonds that are investment grade quality at the time of investment. Under normal market conditions, the Trust intends to invest its assets primarily in a diversified portfolio of investment grade bonds, which may include, but are not limited to, corporate bonds, U.S. government and agency securities and mortgage-related securities. The Trust may invest up to 25% of its total managed assets in bonds that, at the time of investment, are rated Ba/BB or below by Moody’s Investors Service, Inc. (“Moody’s”), S&P Global Ratings ("S&P"), Fitch Ratings (“Fitch”) or another nationally recognized rating agency or bonds that are unrated but judged to be of comparable quality by the investment adviser. The Trust may invest up to 10% of its total managed assets in bonds issued in foreign currencies. The Trust may invest directly in such securities or synthetically through the use of derivatives.

No assurance can be given that the Trust’s investment objective will be achieved.

Risk Factors [Table Text Block]

10.

PRINCIPAL RISKS

In the normal course of business, the Trusts invest in securities or other instruments and may enter into certain transactions, and such activities subject each Trust to various risks, including among others, fluctuations in the market (market risk) or failure of an issuer to meet all of its obligations. The value of securities or other instruments may also be affected by various factors, including, without limitation: (i) the general economy; (ii) the overall market as well as local, regional or global political and/or social instability; (iii) regulation, taxation, tariffs or international tax treaties between various countries; or (iv) currency, interest rate and price fluctuations. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Trusts and their investments.

Illiquidity Risk: Each Trust may invest without limitation in illiquid or less liquid investments or investments in which no secondary market is readily available or which are otherwise illiquid, including private placement securities. A Trust may not be able to readily dispose of such investments at prices that approximate those at which a Trust could sell such investments if they were more widely traded and, as a result of such illiquidity, a Trust may have to sell other investments or engage in borrowing transactions if necessary to raise funds to meet its obligations. Limited liquidity can also affect the market price of investments, thereby adversely affecting a Trust’s NAV and ability to make dividend distributions. Privately issued debt securities are often of below investment grade quality, frequently are unrated and present many of the same risks as investing in below investment grade public debt securities.

Market Risk: Each Trust may be exposed to prepayment risk, which is the risk that borrowers may exercise their option to prepay principal earlier than scheduled during periods of declining interest rates, which would force each Trust to reinvest in lower yielding securities. Each Trust may also be exposed to reinvestment risk, which is the risk that income from each Trust’s portfolio will decline if each Trust invests the proceeds from matured, traded or called fixed-income securities at market interest rates that are below each Trust portfolio’s current earnings rate.

Municipal securities are subject to the risk that litigation, legislation or other political events, local business or economic conditions, credit rating downgrades, or the bankruptcy of the issuer could have a significant effect on an issuer’s ability to make payments of principal and/or interest or otherwise affect the value of such securities. Municipal securities can be significantly affected by political or economic changes, including changes made in the law after issuance of the securities, as well as uncertainties in the municipal market related to, taxation, legislative changes or the rights of municipal security holders, including in connection with an issuer insolvency. Municipal securities backed by current or anticipated revenues from a specific project or specific assets can be negatively affected by the discontinuance of the tax benefits supporting the project or assets or the inability to collect revenues for the project or from the assets. Municipal securities may be less liquid than taxable bonds, and there may be less publicly available information on the financial condition of municipal security issuers than for issuers of other securities.

Valuation Risk: The market values of equities, such as common stocks and preferred securities or equity related investments, such as futures and options, may decline due to general market conditions which are not specifically related to a particular company. They may also decline due to factors which affect a particular industry or industries. A Trust may invest in illiquid investments. An illiquid investment is any investment that a Trust reasonably expects cannot be sold or disposed of in current market conditions in seven calendar days or less without the sale or disposition significantly changing the market value of the investment. A Trust may experience difficulty in selling illiquid investments in a timely manner at the price that it believes the investments are worth. Prices may fluctuate widely over short or extended periods in response to company, market or economic news. Markets also tend to move in cycles, with periods of rising and falling prices. This volatility may cause each Trust’s NAV to experience significant increases or decreases over short periods of time. If there is a general decline in the securities and other markets, the NAV of a Trust may lose value, regardless of the individual results of the securities and other instruments in which a Trust invests. A Trust’s ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third-party service providers.

The price a Trust could receive upon the sale of any particular portfolio investment may differ from a Trust’s valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair valuation technique or a price provided by an independent pricing service. Changes to significant unobservable inputs and

assumptions (i.e., publicly traded company multiples, growth rate, time to exit) due to the lack of observable inputs may significantly impact the resulting fair value and therefore a Trust’s results of operations. As a result, the price received upon the sale of an investment may be less than the value ascribed by a Trust, and a Trust could realize a greater than expected loss or lesser than expected gain upon the sale of the investment.

Counterparty Credit Risk: The Trusts may be exposed to counterparty credit risk, or the risk that an entity may fail to or be unable to perform on its commitments related to unsettled or open transactions, including making timely interest and/or principal payments or otherwise honoring its obligations. The Trusts manage counterparty credit risk by entering into transactions only with counterparties that the Manager believes have the financial resources to honor their obligations and by monitoring the financial stability of those counterparties. Financial assets, which potentially expose the Trusts to market, issuer and counterparty credit risks, consist principally of financial instruments and receivables due from counterparties. The extent of the Trusts’ exposure to market, issuer and counterparty credit risks with respect to these financial assets is approximately their value recorded in the Statements of Assets and Liabilities, less any collateral held by the Trusts.

A derivative contract may suffer a mark-to-market loss if the value of the contract decreases due to an unfavorable change in the market rates or values of the underlying instrument. Losses can also occur if the counterparty does not perform under the contract.

For OTC options purchased, each Trust bears the risk of loss in the amount of the premiums paid plus the positive change in market values net of any collateral held by the Trusts should the counterparty fail to perform under the contracts. Options written by the Trusts do not typically give rise to counterparty credit risk, as options written generally obligate the Trusts, and not the counterparty, to perform. The Trusts may be exposed to counterparty credit risk with respect to options written to the extent each Trust deposits collateral with its counterparty to a written option.

With exchange-traded options purchased and exchange-traded futures and centrally cleared swaps, there is less counterparty credit risk to the Trusts since the exchange or clearinghouse, as counterparty to such instruments, guarantees against a possible default. The clearinghouse stands between the buyer and the seller of the contract; therefore, credit risk is limited to failure of the clearinghouse. While offset rights may exist under applicable law, a Trust does not have a contractual right of offset against a clearing broker or clearinghouse in the event of a default (including the bankruptcy or insolvency). Additionally, credit risk exists in exchange-traded futures and centrally cleared swaps with respect to initial and variation margin that is held in a clearing broker’s customer accounts. While clearing brokers are required to segregate customer margin from their own assets, in the event that a clearing broker becomes insolvent or goes into bankruptcy and at that time there is a shortfall in the aggregate amount of margin held by the clearing broker for all its clients, typically the shortfall would be allocated on a pro rata basis across all the clearing broker’s customers, potentially resulting in losses to the Trusts.

Geographic/Asset Class Risk: A diversified portfolio, where this is appropriate and consistent with a fund’s objectives, minimizes the risk that a price change of a particular investment will have a material impact on the NAV of a fund. The investment concentrations within each Trust’s portfolio are disclosed in its Schedule of Investments.

The Trusts invest a significant portion of their assets in high yield securities. High yield securities that are rated below investment-grade (commonly referred to as “junk bonds”) or are unrated may be deemed speculative, involve greater levels of risk than higher-rated securities of similar maturity and are more likely to default. High yield securities may be issued by less creditworthy issuers, and issuers of high yield securities may be unable to meet their interest or principal payment obligations. High yield securities are subject to extreme price fluctuations, may be less liquid than higher rated fixed-income securities, even under normal economic conditions, and frequently have redemption features.

The Trusts invest a significant portion of their assets in fixed-income securities and/or use derivatives tied to the fixed-income markets. Changes in market interest rates or economic conditions may affect the value and/or liquidity of such investments. Interest rate risk is the risk that prices of bonds and other fixed-income securities will decrease as interest rates rise and increase as interest rates fall. The Trusts may be subject to a greater risk of rising interest rates during a period of historically low interest rates. Changing interest rates may have unpredictable effects on markets, may result in heightened market volatility, and could negatively impact the Trusts’ performance.

The Trusts invest a significant portion of their assets in securities of issuers located in the United States. A decrease in imports or exports, changes in trade regulations, inflation and/or an economic recession in the United States may have a material adverse effect on the U.S. economy and the securities listed on U.S. exchanges. Proposed and adopted policy and legislative changes in the United States may also have a significant effect on U.S. markets generally, as well as on the value of certain securities. Governmental agencies project that the United States will continue to maintain elevated public debt levels for the foreseeable future which may constrain future economic growth. Circumstances could arise that could prevent the timely payment of interest or principal on U.S. government debt, such as reaching the legislative “debt ceiling.” Such non-payment would result in substantial negative consequences for the U.S. economy and the global financial system. If U.S. relations with certain countries deteriorate, it could adversely affect issuers that rely on the United States for trade. The United States has also experienced increased internal unrest and discord. If these trends were to continue, they may have an adverse impact on the U.S. economy and the issuers in which the Trusts invest.

Certain Trusts invest a significant portion of their assets in securities backed by commercial or residential mortgage loans or in issuers that hold mortgage and other asset-backed securities. When a fund concentrates its investments in this manner, it assumes a greater risk of prepayment or payment extension by securities issuers. Changes in economic conditions, including delinquencies and/or defaults on assets underlying these securities, can affect the value, income and/or liquidity of such positions. Investment percentages in these securities are presented in the Schedules of Investments.

Share Price [Table Text Block]

Market Price and Net Asset Value Per Share Summary

	06/30/25	12/31/24	Change	High	Low
Closing Market Price	$ 9.72	$ 10.46	(7.07 )%	$ 11.00	$ 9.50
Net Asset Value	10.06	10.30	(2.33 )	10.59	9.91

Capital Stock, Long-Term Debt, and Other Securities [Abstract]

Capital Stock [Table Text Block]

11.

CAPITAL SHARE TRANSACTIONS

BHK, BTZ and BGT is authorized to issue an unlimited number of shares, par value $0.001, all of which were initially classified as Common Shares. HYT is authorized to issue 250 million shares, par value $0.10, all of which were initially classified as Common Shares. The Board is authorized, however, to reclassify any unissued Common Shares to Preferred Shares without the approval of Common Shareholders.

Common Shares

As of the close of business on May 27, 2025, BHK issued transferrable rights to its Common Shareholders of record, entitling the holders of those rights to subscribe for shares of BHK’s common stock (the “Offer”). Shareholders received one right for each outstanding Common Share owned on the record date. The rights entitled their holders to purchase one new Common Share for every three rights held (1-for-3). The Offer expired on June 18, 2025. BHK received from the Offer gross proceeds of $166,476,836 for the issuance of 18,056,056 Common Shares. The rights offering resulted in $(0.14) or (1.41)% NAV dilution since the Common Shares were issued below BHK’s NAV. BHK received the entire proceeds from the shares issued under the Offer since the Manager agreed to pay for all expenses (including sales commissions) related to the Offer.

For the periods shown, shares issued and outstanding increased by the following amounts as a result of dividend reinvestment:

	Six Months Ended	Year Ended
Trust Name	06/30/25	12/31/24
BHK	47,771	109,695
HYT	622,491	1,085,559
BGT	43,040	65,437

For the six months ended June 30, 2025, and the year ended December 31, 2024, shares issued and outstanding remained constant for BTZ.

BHK, HYT and BGT have filed a prospectus with the SEC allowing them to issue an additional 15,000,000, 45,000,000 and 11,000,000 Common Shares, respectively, through an equity shelf program (a “Shelf Offering”). Under the Shelf Offering, BHK, HYT and BGT, subject to market conditions, may raise additional equity capital from time to time in varying amounts and utilizing various offering methods at a net price at or above each Trust’s NAV per Common Share (calculated within 48 hours of pricing). As of period end June 30, 2025, 15,000,000, 29,238,378 and 5,784,848 Common Shares, respectively, remain available for issuance under the Shelf Offering. During the period ended June 30, 2025, BHK, HYT and BGT issued 0, 5,963,899 and 2,074,747 shares, respectively, under the Shelf Offering. See Additional Information - Shelf Offering Program for additional information.

Initial costs incurred by BHK, HYT and BGT in connection with their Shelf Offerings are recorded as “Deferred offering costs” in the Statements of Assets and Liabilities. As shares are sold, a portion of the costs attributable to the shares sold will be charged against paid-in-capital. Any remaining deferred charges at the end of the Shelf Offering period will be charged to expense.

Outstanding Securities [Table Text Block]

BHK, BTZ and BGT is authorized to issue an unlimited number of shares, par value $0.001, all of which were initially classified as Common Shares.

Illiquidity Risk [Member]

General Description of Registrant [Abstract]

Risk [Text Block]

Market Risk [Member]

General Description of Registrant [Abstract]

Risk [Text Block]