The interchange fee is a charge paid by the card acquiring payment service provider to the card-issuing payment service provider for every card-based payment transaction.

The interchange fee is a component of merchant fees and, where cardholders are consumers, its caps are legally set (Regulation (EU) 2015/751 of the European Parliament and of the Council of 29 April 2015 on interchange fees for card-based payment transactions).

Presently, in Portugal, for debit-card-based payment transactions, the interchange fee cannot be more than 0.2% of the transaction value. In credit-card-based payment transactions, this fee cannot be more than 0.3% of the transaction value.