Build on Rieck

Invoicing, payments, reminders and debt collection as an API. Your UI, your system of record — our engine, our compliance.

Get started in 5 minutes API reference OpenAPI spec

curl -X POST https://app.rieck.nu/api/v1/invoices?issue=true&send=true \
  -H "Authorization: Bearer $RIECK_API_KEY" \
  -H "Idempotency-Key: order-2041" \
  -d '{
    "customer": { "type": "company", "name": "Acme ApS", "cvr": "12345678",
                  "email": "ap@acme.example" },
    "lines": [{ "description": "Consulting", "quantity": 10, "unitPriceOere": 95000 }]
  }'

One call: customer (find-or-create) → invoice → sequential number + locked PDF → sent. Unpaid? The reminder engine and debt collection take it from there — lawfully.

What makes it different

The whole chain, one API

Most billing APIs stop when the invoice is overdue. Here the same resource flows through §9b-compliant reminders into real debt collection — POST /invoices/{id}/collect is one call, not a hand-off to another vendor.

Compliance is enforced, not documented

Statutory reminder fees, four-eyes approval on dunning flows, immutable issued invoices, unbroken number series — the database enforces the floor. You configure aggressiveness; you cannot configure your way into a lawsuit.

Idempotent by contract

Every mutating call requires an Idempotency-Key. Same key, same payload — same response, replayed. Payments book on your key. Retry fearlessly.

Events you can trust

Signed webhooks (standardwebhooks) with replay, plus a pull feed (GET /v1/events?since=) in the exact delivery shape — downtime never costs you data.

Start here

Get started in 5 minutes Key, first call, conventions.

Integration cookbook Webshop, accounting system, own ERP, payment links only.

TypeScript SDK @rieck/api — typed errors, retries, webhook verification.

Webhooks Signature verification, event catalogue, replay.