The banking term for spending beyond the available funds in a deposit account is an overdraft.
An overdraft occurs when a payment, withdrawal, or transaction causes an account balance to fall below zero or otherwise exceed the funds available under the bank’s rules. Depending on the account and the bank, the transaction may be paid, declined, or covered through an arranged overdraft facility or linked account.
An arranged overdraft is agreed in advance and may have an interest rate or fee. An unarranged overdraft occurs without that prior agreement, although exact terminology and consumer protections differ among countries. The cost is not automatically the same as the cost of a credit card or personal loan.
Overdraft protection can connect a checking account to savings, a credit line, or another funding source. That service may reduce declined payments, but it can still involve fees or interest. Customers should distinguish the account balance shown by a bank from the available balance, which may reflect pending transactions and holds.