Guides
KSeF Kit guides
Straight-to-the-point KSeF 2.0 guides — the mandate, structured invoices, corrections and the Stripe integration. No fluff.
Basics
- KSeF Mandatory 2026: Deadlines, Thresholds, Who KSeF is mandatory from 2026. See the deadlines, turnover thresholds, who must issue structured invoices, and what the 5 August 2025 act changed.
- UPO in KSeF — what the receipt confirmation is UPO is proof your invoice reached KSeF. Learn what UPO is, how it differs from the KSeF number, and why you should archive every confirmation.
How it works
- How to Issue a Structured Invoice in KSeF A practical step-by-step: how an FA(3) structured invoice is built, how to send it to KSeF, sign the session, and get your KSeF number and UPO.
- KSeF QR Codes — KOD I, KOD II and Offline Mode QR codes on the KSeF invoice: KOD I for online, KOD I + KOD II for offline24. How they work, where they come from, and why the API never returns them.
- KSeF Correction Invoice (KOR): How to Fix a Filing How to issue a KOR correction invoice in KSeF: reference the original's KSeF number, use the FA(3) format, and handle common correction scenarios.
Selling abroad
- Export Invoices and B2B Sales Abroad in KSeF Does an invoice to a foreign B2B customer go to KSeF? We explain which export sales are covered, which are exempt, and how to file them.
- NBP Exchange Rates on Invoices in KSeF Foreign-currency invoice in KSeF: which NBP rate to use, from which day, and how to avoid VAT conversion errors. One clear rule with an example.
Stripe + KSeF
- Stripe KSeF Integration — Automatic Invoices Connect Stripe to KSeF: every finalized Stripe invoice is filed automatically as FA(3), with the KSeF number and UPO written back to the invoice.
- What Customer Data to Collect in Stripe to File to KSeF Selling worldwide through Stripe, including the EU? See what customer data (country, NIP, EU VAT) to collect so invoices file to KSeF with the right VAT.
- Free KSeF for Stripe — file invoices at no cost Can you file invoices to KSeF for free? Yes — a free production tier for Stripe users, no card required. See what it covers and how to start.