Guide

Quick Start

Convert your first invoice with the EInvoiceAPI in under 2 minutes.

1. Create a free account

Head to console.aethar.dev/register and sign up with your email. You'll get instant access to the Free tier — 100 requests per day, no credit card required.

2. Generate an API key

In the Aethar Console, open the API Keys page and click Create key. Copy the key value — it's shown only once. Keys start with the prefix ei_ for EInvoiceAPI.

Keep your key secret. Treat it like a password. Never commit it to git or embed it in client-side code.

3. Make your first request

Convert an EN 16931 invoice JSON to Peppol BIS 3.0 XML:

curl -X POST "https://einvoice.aethar.dev/api/v1/convert" \
  -H "X-API-Key: ei_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{"invoice":{"invoice_number":"2026-001","issue_date":"2026-04-11","supplier":{"name":"Aethar Systems GmbH","vat_id":"DE000000000"},"customer":{"name":"Acme GmbH","vat_id":"DE000000001"},"line_items":[{"description":"Consulting","quantity":1,"unit_price":1000}],"currency":"EUR"},"target_format":"peppol_bis_3","output":"json"}'

You should see a 200 response with a download_url pointing at the generated XML.

4. Next steps

Browse the full endpoint reference in the left sidebar. Every endpoint has a runnable code sample in curl, Python, and Node.js.

For production workloads, check the Rate Limits and Errors guides to handle non-200 responses gracefully.