A bank generally cannot simply reach into your checking account and grab money to cover an unpaid credit card balance, even if the bank issued both accounts. Federal law specifically limits a credit card issuer’s ability to offset credit card debt against money sitting in a consumer’s deposit account.
That matters when a credit card bill goes unpaid and the checking account happens to sit at the same institution. A missed payment can cause plenty of headaches, but it does not normally give the card issuer a blank check to raid the account. There are, however, some important exceptions that can change the answer.