1. Why an API instead of another invoice system
If your source data already exists, copying it into another tool is usually the wrong workflow. The API connects to your existing billing logic.
BOFU API
German e-invoicing API for structured invoice data
Your software already has the invoice data. Fakturai gives that workflow a clear API boundary: structured data in, ZUGFeRD / Factur-X output out, technical validation report attached.
It is not a new accounting suite. It is a focused layer for teams that need German e-invoice output from an existing SaaS, ERP, marketplace or back-office system.
Public proof
The proof is a real run against the production API on 2026-11-04 with synthetic data: one request JSON with a Munich buyer, EUR currency, invoice date, due date, service period, one line item and 19 percent VAT. Seller details come from the test account's seller profile.
For the generated invoice in ZUGFeRD / Factur-X EN 16931 format, the technical validation report shows validation_status: passed, KoSIT accept, pdfa_compliant: true, hard_failure_count: 0 and advisory_count: 6. The six advisories come from XRechnung and Peppol rules and are not a rejection reason for B2B.
Note: Technical format validation does not replace the issuer's responsibility for invoice content, tax treatment, or archival.
sample invoice JSON · technical validation report · ZUGFeRD / Factur-X output
2. The technical flow
Your system sends structured invoice data. Fakturai generates ZUGFeRD / Factur-X output and runs a technical format validation.
3. What the proof shows
The proof shows the request, generated PDF, embedded XML and the validation report for exactly this invoice, each with SHA-256. It does not provide tax advice or an archive policy.
4. Where Fakturai fits
SaaS billing, marketplace invoicing, internal ERP flows, agency automation and back-office workflows with an existing invoice data source.
5. Where Fakturai does not fit
Teams looking for a full accounting suite, invoice UI, tax advice, archive strategy or content approval workflow.