Company: MYI
Filing Date: 2025-09-05
Form Type: 424B3
Source: 0001193125-25-196285
Chunk: 430

Company: BLACKROCK MUNIYIELD QUALITY FUND III, INC.
Filing Date: 2025-09-05
Form: 424B3
Chunk 430
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. Good intrinsic capacity for timely payment of financial commitments. |

| F3 | Fair Short-Term Credit Quality. The intrinsic capacity for timely payment of financial commitments is 
 adequate.                                                                                             |

| B | Speculative Short-Term Credit Quality. Minimal capacity for timely payment of financial commitments, plus 
 heightened vulnerability to near term adverse changes in financial and economic conditions.               |

| C | High Short-Term Default Risk. Default is a real possibility. |

| RD | Restricted Default. Indicates an entity that has defaulted on one or more of its financial commitments, 
 although it continues to meet other financial obligations. Typically applicable to entity ratings only. |

| D | Default. Indicates a broad-based default event for an entity, or the default of a short-term obligation. |

A-8

APPENDIX B

| Applies to the following types of Funds                                             
 registered under the 1940 Act:  Index Equity Mutual Funds and Exchange-Traded Funds 
 Open-End Active and Fixed Income Index Mutual Funds and Exchange-Traded Funds       
 Money Market Funds  Closed-End Funds  Other                                         |

Objective and Scope Set forth below is the Closed-EndFund Proxy Voting Policy. Policy / Document Requirements and Statements The Boards of Trustees/Directors (the “Directors”) of the closed-endfunds advised by BlackRock Advisors, LLC (“BlackRock”), (the “Funds”) have the responsibility for the oversight of voting proxies relating to portfolio securities of the Funds, and have determined that it is in the best interests of the Funds and their shareholders to delegate the responsibility to vote proxies to BlackRock as part of BlackRock’s authority to manage, acquire and dispose of account assets, all as contemplated by the Funds’ respective investment management agreements. BlackRock has adopted the BlackRock Active Investment Stewardship Global Engagement and Voting Guidelines (as from time to time amended, the “Guidelines”) governing proxy voting by accounts managed by BlackRock. BlackRock will cast votes on behalf of each of the Funds covered by this policy on specific proxy issues in respect of securities held by each such Fund (or may refrain from voting) in accordance with the Guidelines; provided, however, that in the case of underlying closed-endfunds (including business development companies and other similarly-situated asset pools) held by the Funds that have, or are proposing to adopt, a classified board structure, BlackRock will typically (a) vote in favor of proposals to adopt classification and against proposals to eliminate classification, and (b