A per-transaction fee is a fixed amount charged for every payment processed, whatever its value. Payment providers commonly combine it with a percentage fee, as in a price of 2.9 per cent plus 30 cents per card transaction, so that the fixed part covers costs that do not vary with size, such as authorisation messages, fraud checks and network charges. Per-transaction fees also appear in other places: card networks and processors charge them to acquirers, banks charge them for ACH or wire transfers, and gateways may add an authorization fee or gateway fee per attempt. The effect depends on ticket size. On a 200 unit sale, a 0.30 fixed fee is 0.15 per cent; on a 2 unit sale it is 15 per cent, which is why low-value merchants often seek small-ticket or micropayment pricing. Merchants comparing offers should calculate their blended transaction cost across realistic transaction sizes.