Adding "pay now" to an app or website looks simple from the outside. In practice, the button is the easy part. What makes or breaks a payment integration is everything that happens when things don't go to plan.
1. Choose the right gateway
Compare fees, but also payout times, supported cards and wallets, currencies, and how well the gateway is known by your customers. A cheaper gateway that customers don't trust will cost you more in abandoned checkouts.
2. Design the unhappy paths first
Declined cards, 3-D Secure challenges, timeouts, double clicks, partial refunds, chargebacks. Each one needs a clear message for the customer and a clear record for your team. We design these flows before the happy path, because that's where trust is won or lost.
3. Reconciliation
Every payment, refund and settlement should match between your system, the gateway and your bank. If your finance team is matching them by hand in a spreadsheet, that's a sign the integration isn't finished.
4. Test properly in the sandbox
Use the gateway's test cards to run every scenario: success, decline, insufficient funds, refunds and webhooks arriving late or twice. Then run a small number of real transactions before full launch.
5. Go live with monitoring
After launch, watch success rates, failed payments and webhook errors closely for the first few weeks. Small problems caught early save a lot of support tickets later.
How long does it take?
A standard integration often takes one to three weeks, depending on the gateway, the platform and how much testing the provider requires before approving go-live.