Account verification, in payments, usually means bank account verification, the process of confirming that a bank account is real, open and able to receive or send money, and that it belongs to the person or business named. That entry describes the methods in detail.
Payment firms, payroll providers, lenders and marketplaces verify accounts before adding them as a funding source or payout destination. Common methods include instant checks through an account information API, name-matching services such as Confirmation of Payee, micro-deposits that the customer confirms, and, in the United States, a zero-dollar ACH prenotification sent through the network before live payments.
The phrase is broader than its bank meaning. In online services it can also mean confirming an email address, phone number or user profile, and in card payments a zero-value authorization is sometimes described as card account verification. When the question is specifically whether the named person owns the account, the narrower term account ownership verification is used.