KSeF for Shopify stores — what to do before 2027
A short guide written for the store owner. Plain language, no statute quotes: what changes in your store, and in what order to sort it out.
Who KSeF applies to
KSeF (Krajowy System e-Faktur, Poland's national e-invoicing system) covers taxpayers registered in Poland who invoice other businesses. If you sell B2B — wholesale, against a tax ID, on deferred payment — it applies to you directly, wherever you personally happen to live.
Consumer sales (B2C) are out of scope: receipts and invoices for private individuals stay outside the system. In practice Shopify stores are mixed, so the problem is not "whether" but splitting one order stream into two — and making sure an order with a tax ID never lands in the wrong one.
The dates that matter
April 2026 — issuing structured invoices becomes mandatory for all VAT taxpayers. The largest sellers (over 200 m zł of sales in 2024) have been issuing through KSeF since 1 February 2026 — and from that date every business receives its purchase invoices in the system. 1 January 2027 — the sanctions in art. 106ni of the VAT act take effect: up to 100% of the VAT on an invoice issued outside KSeF. No financial penalties are imposed between 1 February and 31 December 2026 — but tax-penal liability applies throughout. Until the end of 2026 a taxpayer whose gross sales in a given month stay under 10,000 zł may issue paper or electronic invoices outside KSeF.
The practical conclusion: 2026 exists so you can clean up buyer data with a clear head. The same project done in December is the same project — only with penalties in the background.
What FA(3) and UPO are
FA(3) is the current version of the structured-invoice schema — an XML file with strictly defined fields. "Structured" means PDFs and scans stop being an invoice as far as the system is concerned: what counts is a document in the schema, accepted by KSeF.
UPO (Urzędowe Poświadczenie Odbioru, the official confirmation of receipt) proves KSeF accepted the document, together with the number identifying the invoice. It is your proof of filing — worth keeping on the order, not in a separate folder.
How to issue a KSeF token
For any tool to file invoices on your behalf it needs authorisation in KSeF. The short version: you authenticate in the Ministry of Finance application — with a qualified electronic signature (podpis kwalifikowany), a company seal (pieczęć firmowa), or the Trusted Profile (Profil Zaufany) of an authorised person — grant the invoicing permission, generate a token and paste it into the app's configuration. The token is a secret: treat it like online-banking credentials and never send it by e-mail.
We will publish the full step-by-step instructions, with screenshots, as a separate guide before the app launches.
Direct filing or via Fakturownia
There are two sensible routes. Direct: the invoice is built from the Shopify order and goes straight to KSeF — fewest moving parts, the shortest path from order to UPO, the whole history in one place. Through an accounting system (Fakturownia, inFakt): the document is created where your accountant works and their software handles KSeF — convenient when accounting already issues some invoices by hand.
The choice comes down to one thing: who in your company owns the invoicing process. If it is the store — file directly. If it is accounting — integrate with their system. Both need the same foundation: a complete, valid tax ID on every B2B order.