Card interchange fees and merchant service charges: understand what is inside the card-processing price

A merchant's card-processing cost is not one single fee. The merchant service charge can include interchange paid through the acquirer to the card issuer, card-scheme and processing costs, and the acquirer's own margin or service charges. Understanding those components makes provider comparisons much more meaningful.

Interchange is paid within the card-payment chain, not directly by the shopper

The Payment Systems Regulator says that for most Visa and Mastercard transactions the merchant's acquirer pays an interchange fee to the cardholder's issuing bank. That cost generally forms part of the merchant service charge paid by the retailer or merchant.

The customer usually sees only the purchase price. Finance sees the cost later in the acquiring statement or net settlement. That is why gross card revenue, acquiring fees and net bank cash should be reconciled separately.

Domestic UK consumer interchange is capped at 0.2 percent debit and 0.3 percent credit where the rules apply

The UK Interchange Fee Regulation currently caps certain domestic consumer debit and prepaid card interchange at 0.2 percent and consumer credit card interchange at 0.3 percent where the merchant, acquirer and issuer are all within the UK and the transaction is in scope.

Those caps do not mean the merchant's total fee is 0.2 or 0.3 percent. The acquirer can charge other components, and commercial, cross-border or other excluded transactions can follow different pricing. Use the cap only to understand one component of the stack.

Merchant service charge includes more than interchange

The PSR describes the merchant service charge as the charge the merchant pays to its card-acquiring provider. It can reflect interchange, card-scheme and processing fees and the acquirer's own commercial pricing.

Statements can also contain terminal rental, authorisation, PCI, gateway, chargeback or other service fees. Build an effective-cost calculation by dividing total acquiring cost by card turnover for the same period, then break out fixed and variable components.

Your card mix determines the effective rate

A merchant serving mostly UK consumers can have a different cost profile from a B2B merchant that accepts many commercial cards or an ecommerce exporter receiving foreign-issued cards. The statutory domestic consumer caps do not eliminate those differences.

When comparing quotes, give providers the same historical card mix. A 0.5 percent headline rate can be meaningless if it applies only to a narrow card category and expensive supplements apply to the transactions the merchant actually receives.

Use three to six months of real statements when renegotiating

Collect card turnover, transaction count, average ticket, domestic versus international mix, debit versus credit, commercial cards, refunds and chargebacks. Ask the new acquirer to price that portfolio rather than a hypothetical merchant profile.

Then compare settlement timing and operational features as well as price. A provider saving £300 per month in fees but delaying £200,000 of weekly cash by an extra day changes working-capital needs. Effective cost includes cash timing and back-office workload.

The PSR continues to work on card-fee competition in 2026

The PSR's 2026 to 2027 work programme says it is continuing action on card fees, including cross-border interchange and remedies relating to domestic scheme and processing fees. Merchants should therefore expect the regulatory picture around some card-price components to continue evolving.

Use current statements and current rules when renegotiating rather than relying on a fee article written several years earlier. Card pricing changes quickly, and the merchant's own transaction mix can change even faster.

Build a monthly card-cost waterfall. Start with gross card turnover, then show interchange-related cost where available, scheme and processing charges, acquirer margin, terminal or gateway charges, refunds, chargeback fees and any FX-related merchant cost. This turns a confusing acquiring statement into an effective percentage management can compare over time.

When negotiating, ask the provider to identify which parts of pricing it controls and which are pass-through. A merchant may be able to negotiate the acquirer margin while statutory interchange or scheme charges remain outside the acquirer's control. That distinction prevents management from expecting a provider switch to eliminate costs that every acquirer must pass through.

Run the same effective-cost calculation before and after any pricing change. If the acquirer reduces its quoted margin but the merchant's card mix shifts toward commercial or international cards, the total percentage can still rise. Separate provider pricing from customer-mix effects so management does not blame or praise the acquirer for costs caused by the sales channel.

For multi-site businesses, compare locations on a like-for-like basis. One site can look expensive because it handles more card-not-present or foreign-issued transactions. Central procurement should use consolidated volume to negotiate, while finance keeps enough detail to understand which transaction types actually drive the cost.