The Card Schemes charge a fee to the acquirer for using their network to process a transaction, this is known as a 'Scheme Fee'. Scheme Fees are typically lower than Interchange (at least for Domestic and Intra-regional traffic).

As with all transactional costs, they can be made up of a percentage of the value of transaction and/or a per-item charge, as well as have minimum and maximum absolute values applied.

The below shows the average % and per-item Scheme Fees for UK merchants, for various categories of transaction.

Fees are indicative only. The Scheme Fees applied to your statements may vary.

Visa scheme fees

Domestic: Merchant and Issuer are in the same country
Intra-UK-EEA: Merchant is in the UK and Issuer is in the European Economic Area (EEA), and vice versa, except transactions in and out of Turkey, Israel and Switzerland which will attract Inter-Regional rates.
Intra-Regional: Both Merchant and Issuer are in the European Economic Area (EEA), except transactions in and out of Turkey, Israel and Switzerland which will attract Inter-Regional rates.
Inter-Regional: Merchant is in Europe and Issuer is in other regions

As of 16 October 2021, the UK is no longer considered as part of the European Economic Area.

Mastercard scheme fees

Domestic: Merchant and Issuer are in the same country
Intra-SEPA EUR: Both merchant & Issuer are in SEPA and transaction currency is EUR
Intra-SEPA NEUR: Both merchant & Issuer are in SEPA and transaction currency is not EUR
Intra-Non SEPA: Both or one of the party are outside SEPA region
Inter-Regional: Merchant is in Europe and Issuer is in other regions

Amex scheme fees