Razorpay integration for Flutter apps.

The app asks your backend to create a Razorpay order for a known amount and receipt. The backend returns the order id and key, the Flutter app opens checkout, and Razorpay returns a payment id and signature. The backend verifies that signature with your key secret before marking the order paid.

Skipping server-side verification — or trusting an amount sent from the app — is the most common way Razorpay integrations get exploited.

Users close apps, lose signal and switch devices mid-payment. Razorpay's webhook will still tell you what happened, including failures, refunds and captured payments that the client never reported.

I implement webhook signature validation, idempotent handlers and a status field that the app reads, so the UI always reflects the server's state.

Razorpay subscriptions cover recurring UPI and card mandates. The backend creates the subscription, stores the mandate id, and listens for charged, halted and cancelled events to decide who still has access.

Entitlement is checked server-side on every protected request, not cached forever in the app.

Refunds can be full or partial, and each one needs a record and a customer notification. Settlement reports should reconcile against your own payment table so finance can close the month without exporting CSVs by hand.

For Indian businesses I also wire GST invoice details into the receipt flow.