When you swipe a debit (check) card as credit at a gas pump a message is sent through Visa to your financial institution asking for $1 preauthorization. This is a status check that Visa/MC has approved and guarantees payment to the merchant up to $75. Your financial institution checks the account and sends a message back to the pump with an approval (valid account) or a decline (invalid account). Once preauthorized, you can begin filling your tank. Since banks do not know how much gas you will be pumping, the bank places a limit (hold) on the account for the amount they determine to be sufficient to guarantee payment for the gasoline purchase. The merchant settles all transactions once a day with their processor and the issuing bank receives within 1-2 days. The bank can hold funds against the account until the actual amount is received from the merchant which can take up to 3 days.
When you swipe a debit (check) card as debit at a pump and enter your pin number (on-line debit), a message is sent through a network to your financial institution for a preauthorization amount between $75-$100 depending on the price of gas. The bank checks the account and sends a message back to the pump with an approval (funds available) or a decline (funds not available). Once preauthorized, the pump is set to this amount and you can begin filling your tank. As soon as your financial institution receives this request, there is a temporary hold on the account by the retailer. This hold is supposed to last only as long as you pump gas into your car. When you return the pump handle, a message is sent back to your financial institution immediately that completes the transaction and records the actual amount of the purchase. This amount should replace the preauthorized amount. Each debit network has rules on the amount of time the issuing bank can hold the preauthorization, which is normally 2-3 hours.
QT has no control over the amount of time a preauthorization is held on a customer account by their financial institution.