Close Mint Authority is a permission in the Token-2022 standard that allows a designated authority to permanently close a token mint account, destroying it and recovering the SOL rent. Closing a mint permanently disables all token operations for that mint.

Unlike revoking mint authority (which prevents new tokens from being created but leaves the mint account open), closing the mint is a more drastic action that terminates the token entirely. It is irreversible.

The Close Mint Authority extension must be set at token creation and specifies which account has the ability to close the mint. If not set, the mint cannot be closed.