The verdict in three sentences
A secure, PCI-DSS-compliant online payment integration costs a London SME between 2,000 and 8,000 EUR in setup, plus recurring fees of 1.4 to 2.9 % + 0.25 EUR per transaction. The real work is not the pay button but accounting reconciliation, 3D Secure failure handling and confirmation webhooks. Expect 2 to 5 weeks depending on the number of payment methods and how far you automate reconciliation.
What a payment integration actually covers
Many owners underestimate online payments because they only look at the PSP's headline rate. Total cost combines the technical setup (API integration, checkout, error handling), compliance (PCI-DSS SAQ-A minimum, 3D Secure 2 mandated by PSD2) and operations (reconciliation, disputes, refunds). A checkout that loses 15 % of conversion on the 3DS screen costs far more than 0.3 points of fees.
| Item | 2026 range (EUR) | What it includes |
|---|---|---|
| API integration + checkout | 1,500 - 4,500 | Checkout, card tokenisation, 3DS2, return pages |
| Webhooks + reconciliation | 800 - 2,500 | Payment confirmation, order matching |
| PCI-DSS SAQ-A compliance | 300 - 1,200 | Externalised card field, light audit |
| Testing (failures, refunds) | 600 - 2,000 | 3DS declined, timeout, partial refund scenarios |
| Total setup | 2,000 - 8,000 | Depending on payment methods |
Comparing PSPs on real fees
The headline rate hides big gaps by card type (European, non-EU, commercial) and channel. Here is a 2026 order of magnitude for an SME processing 30,000 EUR/month.
| PSP | EU card fee | Fixed fee | Typical setup | When to choose |
|---|---|---|---|---|
| Stripe | 1.5 % | + 0.25 EUR | 2,000 - 6,000 EUR | Rich API, SaaS, international |
| Mollie | 1.8 % | + 0.25 EUR | 1,800 - 5,000 EUR | EU e-commerce, local methods (iDEAL, Bancontact) |
| Adyen | 1.2 % + interchange | + 0.11 EUR | 4,000 - 12,000 EUR | High volume, omnichannel, > 100k/month |
| PayPlug | 1.4 % | + 0.25 EUR | 1,500 - 4,000 EUR | Small business, simplicity |
| GoCardless (SEPA) | 1 % (cap ~2 EUR) | - | 1,500 - 4,000 EUR | Recurring direct debit, B2B |
On 30,000 EUR/month in cards, moving from 2.9 % to 1.5 % saves roughly 420 EUR per month, over 5,000 EUR a year: enough to pay off a careful setup within one season.
Mini case study
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Claire runs a materials trading SME in London, 42 staff, moving its B2B orders online. Target volume: 80,000 EUR/month, 60 % cards and 40 % recurring SEPA direct debit. Old solution: an aggregator at 2.7 % on everything. New architecture: Stripe at 1.5 % + 0.25 EUR on cards, GoCardless at 1 % on direct debit.
Monthly maths: cards 48,000 EUR x (2.7 % - 1.5 %) = 576 EUR saved, direct debit 32,000 EUR x (2.7 % - 1 %) = 544 EUR saved, that is 1,120 EUR/month or 13,440 EUR/year. The full setup (integration, webhooks, automatic reconciliation) cost her 6,500 EUR, paid off in under 6 months. Bonus: automated reconciliation saves her 6 hours/month of accounting entry.
FAQ
How long does an online payment integration take? Expect 2 to 5 weeks: 1 week for a simple checkout, 2 to 3 more if you add recurring SEPA, automatic reconciliation and partial refunds.
Do I need PCI-DSS certification? If you never host the card number (fields delegated to the PSP via iframe/Elements), you fall under the lightest SAQ-A questionnaire, about 300 to 1,200 EUR a year.
Does 3D Secure hurt my sales? A poorly built checkout can lose 10 to 20 % of conversion on the 3DS2 screen; a careful integration with frictionless authentication limits the loss to 2 to 4 %.
Which PSP for selling internationally? Stripe and Adyen cover the most currencies and local methods; expect fees raised by 1 to 2 % on non-EU cards and plan multi-currency from the start.
Can I combine several PSPs? Yes, smart routing (cards with one, SEPA with another) optimises fees and acceptance rates, but adds 800 to 2,000 EUR of unified reconciliation logic.
Let's scope your project. Share your monthly volume, target payment methods and accounting tool: we will quote the integration and the expected fee savings. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
