Knowledge of a bank account number is sufficient to attempt to debit it. Whether it will appear to succeed or not depends on the bank and a variety of factors.

Knowledge of a bank account number is sufficient to attempt to debit it. Whether it will appear to succeed or not depends on the bank and a variety of factors. Regardless of whether it initially successes, it is (very) reversible. There’s a lot of technical nuance here which I’d ordinarily geek out on but don’t quite have the time to today.