Company: MYI
Filing Date: 2025-09-02
Form Type: N-14 8C/A
Source: 0001193125-25-193985
Chunk: 45

Company: BLACKROCK MUNIYIELD QUALITY FUND III, INC.
Filing Date: 2025-09-02
Form: N-14 8C/A
Chunk 45
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 delivered to two
or more shareholders of the Funds who share an address, unless the Funds have received instructions to the contrary. This practice is commonly called “householding” and it 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. To request a separate copy of any shareholder document or for instructions as to how to request a separate copy of
these documents or as to how to request a single copy if multiple copies of these documents are received, shareholders should contact the respective Fund at the address and phone number set forth above.

The common shares of BlackRock MuniVest Fund II, Inc. are listed on the NYSE under the ticker symbol “MVT,” the common shares of
BlackRock MuniYield Michigan Quality Fund, inc. are listed on the NYSE under the ticker symbol “MIY,” and the common shares of BlackRock MuniVest Fund, Inc. are listed on the NYSE under the ticker symbol “MVF.” The common
shares of BlackRock MuniYield Quality Fund III, Inc. are listed on the NYSE under the ticker symbol “MYI” and will continue to be so listed after the completion of the Reorganizations.

v

This Joint Proxy Statement/Prospectus serves as a prospectus of the Acquiring Fund in connection with each Issuance. No person has been authorized to give any information or make any representation not contained in this Joint Proxy Statement/Prospectus and, if so given or made, such information or representation must not be relied upon as having been authorized. This Joint Proxy Statement/Prospectus does not constitute an offer to sell or a solicitation of an offer to buy any securities in any jurisdiction in which, or to any person to whom, it is unlawful to make such offer or solicitation. TABLE OF CONTENTS

| SUMMARY                                                                      |     |   1 |
| EXPENSE TABLE FOR COMMON SHAREHOLDERS                                        |     |  15 |
| RISK FACTORS AND SPECIAL CONSIDERATIONS                                      |     |  18 |
| Comparison of Risks                                                          |     |  18 |
| Risks Related to the Reorganizations                                         |     |  18 |
| General Risks of Investing in the Acquiring Fund                             |     |  20 |
| INFORMATION ABOUT THE REORGANIZATIONS                                        |     |  43 |
| Description of the Reorganizations                                           |     |