Payment Gateway Providers in the UK: Merchant Comparison

Having UK customers and being eligible for a UK merchant arrangement are different things. Square's UK terms limit use to business purposes in the UK and specify a UK legal resident or a company authorised to do business there. Mollie lists UK-based companies among its supported business locations and requires an IBAN or UK bank account to sign up. Neither statement establishes acceptance of every ownership structure, activity or bank destination. [4][5]

Send each candidate the same short brief: legal entity, ownership, trading website, goods or services, fulfilment period, customer countries and expected processing. Include the activities that complicate the case rather than waiting for underwriting to discover them. Stripe distinguishes prohibited activities from restricted categories requiring additional due diligence; a supported location does not override those conditions. [8] Where a required activity is excluded, remove that arrangement from the shortlist. Where acceptance is unclear, obtain a written answer before paying for implementation.

Ask which company signs the agreement, which provides the regulated payment service and whether another party supplies the gateway technology. Record their responsibilities separately if the proposal involves several entities. A website address or a sales representative's identity cannot answer all three questions.

The FCA advises users of payment providers to find the operating company's name and check its status and relevant permissions on the Financial Services Register. Its firm-checking guidance also explains why matching contact details matters when avoiding impersonation. [6][7] This is a due-diligence step, not a statement that any named provider has been independently cleared here. The FCA separately explains that non-bank payment-provider balances do not have FSCS protection and that safeguarding differs by institution type. [6] Ask how your actual funds flow is protected; do not treat a gateway logo, directory badge or authorisation reference as a bank-deposit guarantee.

For standard UK cards, Stripe publishes 1.5% plus 20p; its premium UK bucket is 2.8% plus 20p. Square's online products use a UK-card tariff of 1.4% plus 25p. Mollie's Visa and Mastercard table separates UK consumer cards at 1.20% plus 20p from UK commercial cards at 2.90% plus 20p. [1][2][3]

Those labels matter. Ask each provider to map a sample of your transactions to its own charge categories. Do not classify cards from the customer's delivery address, or assume every card issued in Britain attracts the lowest price.

Channel differences can be just as costly. Square's fee schedule lists 2.5% for Invoices, Virtual Terminal and Card on File, rather than the online-checkout tariff used below. [2] A business collecting invoices or charging saved cards should price that workflow explicitly. If the quote includes a separate billing service, store subscription or fraud product, add its charges before comparing the final bill.

Suppose a purchase falls into Stripe's standard UK bucket, Square's UK online bucket and Mollie's UK consumer Visa or Mastercard bucket. At £20, the processing charges are 50p, 53p and 44p respectively. At £100 they are £1.70, £1.65 and £1.40. These are arithmetic examples using the published tariffs, not test transactions or offers to a particular merchant. [1][2][3]

For Stripe versus Square, the extra 5p fixed charge on Square is offset by a percentage charge 0.1 percentage points lower when the basket reaches £50: £0.05 divided by 0.001. Both then cost 95p. Below that point Stripe's stated standard-card tariff is lower; above it Square's UK online tariff is lower. This crossover says nothing about premium cards, refunds or operational fit.

Use your distribution of orders, not just a rounded average. A merchant with many small baskets and a few very large orders should calculate both transaction counts and sales value by tariff category.

Suppose there are 2,000 successful £20 orders each month: £40,000 in total. If all qualify for the lower UK buckets above, processing charges are £1,000 at Stripe, £1,060 at Square and £880 at Mollie. Now assume 400 of those payments instead attract Stripe's premium UK tariff and Mollie's UK commercial tariff, while Square's stated UK online rate continues to apply. All cards remain UK-issued, all transactions stay in the same online channel and no currency conversion occurs.

Stripe becomes £1,104: £32,000 × 1.5%, plus £8,000 × 2.8%, plus 2,000 × 20p. Mollie becomes £1,016; Square remains £1,060. The Stripe–Square order reverses without changing sales or order count. These assumed classifications must be checked against real provider reporting; they are not a claim that every provider categorises every card identically.

All totals are processing-only, before other applicable charges and taxes. Mollie's lower figure in these scenarios does not establish the lowest complete cost or the best merchant fit.

Overseas cards need a separate quote. Square's product pricing page shows 2.5% plus 25p for non-UK online cards, while its fee-schedule footnote describes an additional 1.5% international charge applying across card-not-present and API transactions. The relationship between that footnote and the displayed non-UK online rate needs clarification. [2][9] Do not quietly choose the lower reading or add charges together and present the result as a confirmed account price.

Mollie's itemised pricing section lists fees after five monthly payouts for merchants below its stated annual volume threshold, while its FAQ says daily payouts carry no extra fee. [3] Ask for the rule applicable to your account and payout frequency. These uncertainties are why neither foreign-card processing nor payout charges appear in the worked totals.

Request a dated schedule identifying product, card categories, extra charges and exceptions. Attach that schedule to the proposal you evaluate. A low-cost scenario should remain provisional wherever an unresolved fee could change the decision.

A checkout demonstration should answer your operational questions, not just show a successful payment. Ask a developer and a finance colleague to follow the same order through authorisation, capture, partial refund and the payout report. Include a timeout: how will the shop discover whether payment succeeded, and how will it avoid charging again while the outcome is unknown?

For subscriptions, ask how customers give consent, update payment details and cancel, and which charges apply to the renewal route. For delayed delivery, demonstrate how long an authorisation can remain valid and what happens when fulfilment slips. These are acceptance tests to request, not claims that the three providers support identical features.

Then give finance a sample payout containing sales, fees and a refund. Require a trace back to individual orders. An integration that saves a few pounds in processing but creates a recurring reconciliation task may be the more expensive operational choice. Estimate that work before migration.

A small-basket UK retailer should investigate fixed transaction charges and how the store handles refunds. A business selling larger baskets should recalculate the percentage component rather than carry over the small-basket result. A company with substantial commercial-card volume needs the actual tariff mix; a subscription business needs renewal behaviour and customer continuity demonstrated before treating any checkout price as decisive.

Cash availability can be a separate constraint. Request the time from capture to available balance, payout dispatch and bank receipt, alongside any reserve or review conditions. Ask for a worked first month that includes a weekend and a refund. Do not turn a chosen payout frequency into a promise that every sale will be available then.

Finally, price the change itself: implementation, staff training, reporting changes, credential migration and termination obligations. A working current arrangement with a modestly higher transaction bill can be preferable when a replacement's migration risk or cash terms remain unresolved. Set a deadline for obtaining those answers rather than letting an incomplete comparison drift into a contract.