How to Integrate Stripe Payments in Your SaaS MVP

Stripe is the industry standard for SaaS payments in 2026. The documentation is excellent, but there are a dozen decisions to make and gotchas to avoid. This guide walks you through the full integration — from Stripe setup to handling edge cases.

What You'll Build

• Subscription checkout flow via Stripe Checkout
• Webhook handler to sync payment status to your database
• Customer billing portal for self-service subscription management
• Gating features behind active subscription status

Step 1: Stripe Account and Products Setup

1. Create a Stripe account at stripe.com
2. Go to Products → Add Product
3. Create your subscription plan (e.g., 'Pro Plan — $49/month')
4. Note the Price ID (looks like price_1abc123...) — you'll need this
5. Get your API keys from Developers → API Keys

Step 2: Create a Checkout Session

When a user clicks 'Upgrade', create a Stripe Checkout Session on your backend and redirect them to it. Never create checkout sessions on the frontend — this exposes your secret key.

Backend (Supabase Edge Function or Node.js)

• Receive the user's ID and desired plan from the frontend
• Create or retrieve the Stripe Customer for this user
• Create a Checkout Session with the Price ID and customer
• Set success_url and cancel_url for redirect after payment
• Return the session URL to the frontend
• Frontend redirects user to session URL

Step 3: Handle Webhooks (Critical)

Webhooks are the most important part of the integration and the most commonly done wrong. Stripe sends events to your server when things happen (payment succeeded, subscription cancelled, etc.). You MUST listen to these to keep your database in sync.

Webhook Events You Must Handle

• checkout.session.completed — user just paid, activate their account
• customer.subscription.updated — plan changed or trial ended
• customer.subscription.deleted — subscription cancelled, revoke access
• invoice.payment_failed — notify user their payment failed
• invoice.payment_succeeded — renewal payment successful

Webhook Security

Always verify the webhook signature using your Stripe Webhook Secret. Never trust webhook payloads without verification — anyone could send fake events to your endpoint.

Step 4: Billing Portal

Instead of building your own subscription management UI (cancel, upgrade, change card), use Stripe's Customer Portal. It's a hosted page that handles everything. Users can cancel, change plans, update payment methods, and download invoices — for free.

1. Enable Customer Portal in Stripe Dashboard → Settings → Billing
2. Configure allowed actions (cancel, upgrade, downgrade)
3. Create a portal session on your backend when user clicks 'Manage Billing'
4. Redirect user to the portal URL

Step 5: Gate Features Behind Subscription Status

Store the user's subscription status in your database (synced via webhooks). Check this status before allowing access to paid features. Never rely on the frontend to hide features — always check on the backend.

Common Mistakes to Avoid

• Activating accounts after checkout.session.completed without webhook verification
• Not handling failed payments — users get locked out without notice
• Building billing UI from scratch instead of using the Customer Portal
• Not testing with Stripe's test card numbers before going live
• Using your secret key on the frontend (massive security risk)
• Not setting up idempotency — handling the same webhook event twice

Testing Before Go-Live

• Use test API keys (sk_test_...) and test card: 4242 4242 4242 4242
• Test payment failure: card 4000 0000 0000 0002
• Use Stripe CLI to forward webhooks to localhost: stripe listen --forward-to localhost:3000/webhook
• Test every webhook event type before launch