FA(3) validator with auditable sources

Paste a structured invoice XML. Get findings with a quote from the official MF brochure — not a raw parser message.

GitHub Pages is static. The live validator (FastAPI) runs on your machine: python -m fa3check.web → http://127.0.0.1:8000. Below are screenshots from that UI.

fa3-check home: paste XML and validate — Home — paste FA(3) XML, privacy notice next to the field.

Validation result showing SEM-001 with source quote — Result — SEM-001 expanded: what / why / how to fix / source quote.

Rules catalog with brochure quotes — Rules & translations — every entry has a source you can verify without reading code.

Run locally

git clone https://github.com/Iakirmon/ksef-fa3-checker.git
cd ksef-fa3-checker
python3.12 -m venv .venv && .venv/bin/pip install -e ".[dev]"
.venv/bin/python -m fa3check.web

Sample invoices: korpus/zloty/fa3-przyklad-01.xml … -26.xml. Full story: README (English + Polish).

Po polsku

Walidator faktury FA(3) / KSeF. Wklejasz XML, dostajesz zastrzeżenia z cytatem ze źródła MF.

Ta strona na GitHub Pages jest tylko podglądem (screenshoty). Działający walidator odpalasz lokalnie — nic nie wychodzi na zewnątrz.