An authorization fee is a per-request charge that a merchant pays each time it asks a card issuer to approve a payment. It may be charged by the payment gateway, the processor or acquirer, and card networks also levy their own small fees on authorisation messages, which acquirers pass on. Unlike percentage-based charges such as interchange, the authorisation fee is usually a flat amount, and it is often applied whether the request is approved or declined, which is why declines and retries carry a cost. Some providers bundle it into a single per-transaction fee, while others list it separately next to a capture fee or a decline fee. Merchants with many small payments, frequent zero-value checks or high retry volumes feel these fees most, and can reduce them by cutting unnecessary authorisations, using card updater services and tuning payment retry logic.