Payment Gateway Ecommerce: How to Choose and Integrate
A payment gateway for ecommerce authorises card and wallet payments on an online store, applies strong customer authentication under PSD2, and settles the funds to a SEPA bank account. The pricing model, not the brand, is what moves the bill: on 40,000 euro per month in card volume, the difference between a 1.5% flat structure and interchange++ pricing can exceed 200 euro per month. This guide compares fee models, integration paths and security requirements for online stores in 2026.
How an Ecommerce Payment Gateway Works
The flow at checkout has five steps: the store sends a tokenized payment request to the gateway; the gateway triggers 3D Secure 2 authentication (strong customer authentication has been mandatory in the EEA under PSD2 since 2019); the issuer approves or declines; the gateway captures the funds; and the money settles to the merchant's bank account.
Two numbers matter when comparing providers: the authentication rate on 3DS challenges, and the payout time. RoxPay settles within 48 hours to any SEPA bank and processes on PCI DSS Level 1 certified infrastructure, so card data never touches the store's own servers.
Payment Gateway Fees: Flat Rate vs IC++
Flat rate structures: Stripe charges 1.5% + EUR 0.25 on European cards; PayPal bills 3.4% + EUR 0.35 on checkout transactions. Easy to read, but every card is billed the same regardless of its real cost.
Interchange++ (IC++): the gateway passes through the actual interchange of each card (capped at 0.2% for consumer debit and 0.3% for consumer credit in the EU under Regulation 2015/751), adds scheme fees, and charges a fixed markup.
RoxPay: €0.15 + 0.35% to 0.85% (IC++). On 40,000 euro per month with a majority of EU debit cards, total processing cost typically lands between 0.5% and 0.7% including the fixed fee, against 1.5% or more on flat structures: a difference of several hundred euro per month at this volume. For the fee-by-fee method, see the [payment gateway fees comparison](/en/resources/payment-gateway-fees-comparison).
Integration Options: Plugins, SDK and API
Cart plugins: WooCommerce, PrestaShop and Magento all have maintained gateway plugins; a store on one of these carts can go live without custom code. Platform-specific details are covered in the [Magento payment gateway guide](/en/resources/magento-payment-gateway) and the [PrestaShop payment gateway guide](/en/resources/prestashop-payment-gateway).
Hosted fields and redirects: the fastest compliant path, because the card data is collected on infrastructure certified at PCI DSS Level 1, keeping the store in the lightest PCI scope.
REST API with sandbox: for custom checkouts, marketplaces and subscription businesses. Test the full lifecycle in sandbox (authorisation, capture, partial refund, recurring charge) before pointing the production keys, and check webhook reliability and SDK coverage for your stack (PHP, Node, Python) in the technical comparison, not as an afterthought. The end-to-end steps are in the [ecommerce payment integration guide](/en/resources/ecommerce-payment-integration-guide).
Cross-Border Payments and Currency
An online store selling across the EU faces two extra cost drivers: cross-border scheme fees on cards issued outside the acquirer's region, and currency conversion. A [cross-border payment gateway](/en/resources/cross-border-payment-gateway) setup should state both explicitly.
Practical rules: settle in EUR to a SEPA account to avoid conversion on payout; decide whether to price in the customer's currency (higher conversion, some FX cost) or in the store's own currency (no FX cost, slightly lower conversion abroad); and check that Amex and international schemes are included in the standard range, because refusing them loses the whole basket.
Returns also carry cost on cross-border orders: on a partial refund the card schemes do not always return the full original interchange, so every reversed transaction shows a small net cost. Budget for it in the margin model instead of discovering it in the first statement.
Recurring Payments and Subscription Billing
Stores billing on a schedule face a second SCA layer: the first transaction requires strong customer authentication, while subsequent merchant-initiated transactions (card-on-file renewals) can use issuer-accepted exemptions. Failures concentrate exactly on renewal day, which is why the payment method matters as much as the gateway: cards decline on expired numbers and closed accounts, while SEPA direct debit keeps collecting after a card expires.
Cost example: a subscription shop with 3,000 monthly renewals of 39 euro loses 117,000 euro of recurring revenue if 10% of renewals fail and are never recovered; every point of recovery rate is worth 1,170 euro per month here. RoxPay supports recurring billing by card with stored credentials and by [SEPA direct debit for recurring payments](/en/resources/sepa-direct-debit-recurring-payments), with dunning flows configured from the dashboard.
Security, SCA and Chargebacks
3D Secure 2 shifts fraud liability from the merchant to the issuer on authenticated transactions, so enable it on all EU cards; the exemption thresholds (low-value and low-risk transactions) are decided by the issuer, not the store.
PCI scope: with hosted fields or a redirect the store qualifies for SAQ A, the lightest self-assessment; a fully integrated API checkout brings more scope responsibility, which is why the [3D Secure payment gateway](/en/resources/3d-secure-payment-gateway) configuration matters as much as the fee.
Chargebacks: each card scheme runs its own dispute window (typically 120 days from the transaction for most reason codes). Friendly-fraud is the category online stores meet most often; the response process is covered in the [chargeback dispute management guide](/en/resources/chargeback-dispute-management-ecommerce).
Perguntas frequentes
What is the best payment gateway for an online store?
Judge four things: the pricing model (IC++ beats flat rate above roughly 10,000 euro per month), integration effort for your cart, payout time to your bank, and technical support quality. A store on WooCommerce with 15,000 euro per month in card volume will usually pay less on IC++ pricing with a plugin than on a flat-rate provider with the same plugin.
How long do payment gateway payouts take?
RoxPay settles within 48 hours to any SEPA bank account. Many providers work on T+2 to T+5 schedules, which ties up working capital: on 40,000 euro per month, every extra day of payout delay holds roughly 1,300 euro out of the account. Confirm the payout calendar before signing.
Does my online store need PCI DSS certification?
The store itself does not if card data is collected on the provider's certified infrastructure: with hosted fields or a redirect the merchant completes the short SAQ A self-assessment. Full PCI DSS certification (Level 1) is held by the processor, which is what a compliant ecommerce payment gateway must be able to prove.
Can I change payment gateway without rebuilding my store?
Yes, if the checkout is integrated through a plugin or an API abstraction: switching providers means new credentials and re-testing the payment lifecycle, not a new store. Stores with deeply customised checkouts should budget a development sprint for the migration.
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