Accepting credit cards costs the same headline percentage as debit at most UK providers, because they blend the two. What changes your effective rate is the mix: consumer credit is capped higher than debit, and commercial and overseas cards are outside the caps entirely and surcharged accordingly.
Model the mix, not the headline
Take your last twelve months and split it four ways: UK consumer debit, UK consumer credit, commercial, and non UK. Apply each provider's published rate for each category. A business with a fifth of its takings on commercial cards will get a different ranking from one with none, and the headline percentage will have told it nothing.
American Express, decided separately
Most providers price American Express above their headline rate, and some acquire it separately. Zettle is unusual on this shelf in printing one flat rate for major cards including American Express. Whether to accept it at all is a commercial decision about your customers rather than a technical one, since the same terminal takes it.
What you cannot do about it
Surcharging consumer debit and credit cards is banned in the UK, so passing the cost to the customer is not an option for the cards that make up most of your takings. That is why American surcharging vocabulary, convenience fees and card fee notices, does not apply here and why the answer is choosing the right rate rather than recovering it.
Questions people ask about accepting credit card payments
Does accepting credit cards cost more than debit?
Underneath, yes, because UK interchange is capped higher for consumer credit. Most providers blend the two into one advertised percentage, so the difference only shows if the provider prices them separately.
Can I add a surcharge for credit cards in the UK?
Not for consumer cards. Surcharging consumer debit and credit cards is banned in the UK, which is why the American practice of a card fee at the till does not exist here.
Should I accept American Express?
It depends on your customers. Most providers price it above their headline rate; Zettle prints one flat rate covering it. The terminal takes it either way, so this is a margin decision rather than a hardware one.