Invoices for no-code and AI app builders

Your builder makes the app, not the invoice

AI app builders like Lovable, Bolt, Replit or v0 build you an app in hours and connect Stripe. What's missing only shows up when the tax office or your tax advisor (Steuerkanzlei) asks: these tools create a payment, but not an invoice in the sense of German law. There's no structured document under EN 16931, no GoBD archive (GoBD being the German rules for keeping digital records), no VAT logic per country and no DATEV export. Rebuilding all of that yourself is exactly the work you picked a builder to avoid.

Rechnungskit closes that gap with a REST API, at the point where your builder already handles the payment: the server-side function behind your Stripe webhook. One API call turns the sale into a ZUGFeRD invoice with your own number sequence, archived in an audit-proof way and ready for booking in DATEV.

Does your builder fit? An honest overview

It comes down to one question: can your builder make an API call on the server (with a secret key that never reaches the browser) and process Stripe payments through a webhook? If so, the connection works.

• Very well suited, with a dedicated guide: Lovable and Bolt. Both set up edge functions for Stripe, which is the environment the connection needs (Lovable docs, Bolt docs).
• Very well suited: Replit (a real backend plus a secrets store) and v0 by Vercel (Next.js with server-side code, v0 docs). The call goes into your Stripe webhook endpoint.
• Suited with a backend: WeWeb with its own backend or together with Supabase or Xano (WeWeb docs), as well as Bubble (backend workflows) and FlutterFlow (Cloud Functions).
• Needs a layer in between: Framer has no backend for your own server code. There, the call runs through a small serverless function (for example on Cloudflare or Vercel) that you put in between. Softr calls external APIs directly from its workflows on the Professional plan and above; below that you need the same layer in between.
• Probably not needed: builders with their own invoicing feature, such as Wix or Jimdo. Do check whether their documents are EN 16931 e-invoices and how they are archived, though.

The call you add

Whatever builder you use: in the function that processes your Stripe webhook, add a fetch to POST /v1/orders in the success branch. Amounts go in whole cents, the Stripe payment reference goes in paymentRef, and the key comes from the secrets:

// Your builder's backend function, in the Stripe webhook after a successful payment
const res = await fetch('https://api.rechnungskit.de/v1/orders', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${process.env.RECHNUNGSKIT_API_KEY}`,
    'Content-Type': 'application/json',
    'Idempotency-Key': session.id
  },
  body: JSON.stringify({
    orderNo: session.id,
    paymentRef: session.payment_intent, // pi_... from Stripe
    email: session.customer_details?.email,
    billingAddress: {
      name: session.customer_details?.name,
      country_code: session.customer_details?.address?.country, // required for VAT
      postal_code: session.customer_details?.address?.postal_code,
      city: session.customer_details?.address?.city,
      street: session.customer_details?.address?.line1
    },
    items: [{ name: 'Pro plan', quantity: 1, unitGrossCents: 2900, taxRate: 19 }]
  })
})

The invoice isn't created by this call. It's created as soon as the Stripe payment reaches Rechnungskit and matches the order. There is deliberately no paid field.

One-time setup, stated plainly

The code is simple; a few things you set up once:

• Connect Stripe in the dashboard and set it to API (Connections → Connect, with API orders as the sales basis). It's a click, not code.
• Send the country code. Without country_code in the billing address the order is rejected.
• Set an Idempotency-Key. Every POST needs the header; otherwise a duplicate webhook creates two orders.
• Verify the Stripe signature in your builder and retry on 5xx, so no order gets lost.

Show your AI the docs

Rechnungskit publishes a complete OpenAPI 3.1 specification at api.rechnungskit.de/v1/openapi.json. Give it to your builder's AI and ask it to report an order to Rechnungskit in the Stripe webhook after a successful payment. The full reference with working examples is in the API documentation.