When you use a debit card, the merchant sends a confirmation to the Credit Union for an authorization. When the approval is given, the balance in your checking account is reduced or “blocked” by the amount of the purchase. This is known as a pre-authorization hold. The merchant determines the amount of the hold. Greater Alliance CU establishes the length of time the hold remains in place. Typically the hold stays on your account until the funds are transferred to the merchant, or 24 hours.