# Build Payment Gateway Integration in Lovable

- Tool: Lovable Prompts
- Last updated: June 2026

## TL;DR

Paste the starter prompt below into Lovable Build mode and get a complete Stripe integration — checkout, customer portal, and a webhook handler that actually works in Deno. The two gotchas that break every other guide: you must read the request body with req.text() not req.json(), and you must call constructEventAsync not constructEvent. Both are non-negotiable in Deno Edge Functions. A documented build ran this entire flow in under 10 credits in one session.

## Frequently asked questions

### Can I test Stripe in the Lovable preview without deploying?

Yes — Lovable preview URLs are publicly accessible HTTPS URLs, which means Stripe can send webhook callbacks to them. Register your preview URL as a webhook endpoint in Stripe Dashboard (Developers → Webhooks → Add endpoint), select the events you want, and copy the signing secret to Cloud Secrets. You can complete a full test checkout cycle (including webhook processing) without deploying to a custom domain. Just remember to create a separate webhook endpoint when you deploy to production — preview and production have different URLs and need different signing secrets.

### Why does my webhook fail with 'Webhook signature verification failed'?

Almost always because you read the request body with await req.json() instead of await req.text(). JSON parsing re-serializes the bytes in potentially different order or encoding than the original request body that Stripe signed. The constructEventAsync function needs the exact raw bytes as Stripe sent them. Fix: change every occurrence of await req.json() to await req.text() in stripe-webhook/index.ts, and only parse the event data from the already-verified event object that constructEventAsync returns.

### Should I use Stripe, Paddle, or Lemon Squeezy?

Use Stripe if you're primarily selling in the US or UK, want full control over your pricing and customer data, and can handle sales tax compliance yourself (or you're below the registration thresholds in most jurisdictions). Use Paddle or Lemon Squeezy if you sell globally and want zero tax headaches in exchange for a ~2-3% higher fee — both are Merchant of Record services that collect and remit VAT and sales tax on your behalf, which removes a significant compliance burden. Lemon Squeezy is friendlier for solopreneurs and simple digital goods; Paddle handles more complex scenarios like B2B invoicing and seat-based pricing. This prompt kit is built around Stripe but the same constructEventAsync + raw-body webhook pattern applies to Paddle's webhooks.

### How do I handle sales tax and VAT?

With Stripe, you are responsible for calculating, collecting, and remitting sales tax (US) and VAT (EU/UK). Stripe Tax ($0.50/transaction where enabled) can calculate tax automatically and generate reports, but you still file and remit yourself. If this sounds painful, switch to Paddle or Lemon Squeezy (Merchant of Record) — they handle all tax compliance globally for ~5% + 50¢ per transaction. For most early-stage founders under $100K revenue, you're likely below the registration thresholds in most US states and EU member states — consult a tax professional about your specific situation.

### What if my Stripe secret key leaks?

Act immediately: go to Stripe Dashboard → Developers → API keys → Roll the secret key. This generates a new secret key and invalidates the old one within minutes — any requests using the old key will fail. Update STRIPE_SECRET_KEY in Cloud Secrets with the new value. If the leaked key was live mode, also review your Stripe Dashboard → Events log for any suspicious charges made in the window between the leak and the roll. Report unauthorized charges to Stripe's fraud team.

### Can I switch from test mode to live mode without rebuilding?

Yes — it's a configuration change, not a rebuild. Update STRIPE_SECRET_KEY in Cloud Secrets from sk_test_... to sk_live_... Create a new webhook endpoint in Stripe Dashboard (Live mode) pointing at your production URL, and update STRIPE_WEBHOOK_SECRET to the new signing secret. Update the price_ids in Pricing.tsx to live-mode Price IDs. Test with a real $1 charge on your own card and refund immediately. The code and database schema are identical between test and live modes — only the keys and price IDs change.

### Can RapidDev set up Stripe Connect for marketplace payouts?

If your build outgrows this prompt kit and you need custom architecture, RapidDev builds production-grade Lovable apps at $13K-$25K — book a free 30-minute consultation at rapidevelopers.com.

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Source: https://www.rapidevelopers.com/lovable-prompts/lovable-prompts-for-building-payment-gateway-integration
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