KSeF: what your invoicing software needs to support

KSeF — the Krajowy System e-Faktur, Poland's national e-invoicing system — is often described as a new way to send invoices. That undersells the change. Under KSeF an invoice is issued at the moment the Ministry of Finance's system accepts it and assigns it a number. The PDF your customer receives stops being the invoice and becomes a visualisation of one. Software that treats KSeF as an export button will fail you at exactly the wrong moment.

This is the checklist to hold a vendor to, whether you are choosing new invoicing software or deciding whether the software you have will survive the transition.

The capability checklist

1. Structured invoices in the current FA schema, validated before sending. Not "we can generate XML" — the specific, current schema, with client-side validation that tells you which field is wrong rather than returning a rejection code from the ministry.
2. All the authorisation paths your business actually uses. A KSeF token for the system-to-system connection, a qualified electronic seal or signature for a company, and the paper route for granting rights where the electronic one is not available. If you use an accounting office, it needs delegated rights, not your credentials.
3. Capturing and storing the KSeF number and the UPO. The reference number is your proof that the invoice exists. It has to land back on the invoice record, be searchable, and appear on the visualisation you send the customer.
4. Receiving inbound invoices, not just sending. Your suppliers' invoices arrive in the system whether or not you collect them. Software that only pushes outbound leaves you reconciling by hand.
5. Offline handling. There are defined modes for issuing when the system is unreachable, with the invoice queued and submitted once it is back. Ask specifically what happens to the numbering and the customer copy in that window, and whether the visualisation carries the required QR code.
6. Attachments and non-standard content. The structured format does not carry arbitrary PDFs. Ask how the vendor handles attachments, and how anything that does not fit a schema field — long descriptions, delivery notes — is preserved.
7. Corrections and credit notes through the same path. A correcting invoice is a KSeF document too, and it must reference the original's number.
8. Export and archive on the way out. You need the structured files and the numbers, not a report. Ask for the format before you need it.

Authorisation is the part teams underestimate

The technical integration is usually the vendor's problem. Rights management is yours. Decide early who in the company may issue in the company's name, whether your accounting office gets its own delegated access, and what happens when the person holding the qualified signature is on holiday. A token pasted into a shared document is the failure mode to avoid; ask whether the software stores tokens per user, with an audit trail of who issued what.

Questions that expose a thin integration

• "Show me an invoice being rejected." A good product explains the error in Polish, in the invoice form, next to the field.
• "What happens if the system is unavailable for four hours during our invoicing run?"
• "Where do I see my supplier invoices that arrived through KSeF but not by email?"
• "Can my accounting office work in this without using my login?"
• "How do I find an invoice by its KSeF number six months from now?"

On the timetable

The mandatory rollout is phased by taxpayer size, with a further deferral for the smallest issuers, and the schedule has been amended more than once. Do not plan from a date in an article — including this one. Check the Ministry of Finance KSeF pages for the current position, and ask your vendor in writing which phase they consider you to be in and when their support for it goes live.

What does not move is the preparation: the data cleanup, the rights decisions and the test invoices are the same work regardless of which month the obligation starts for you.

What does not change

KSeF changes the form and the route of an invoice, not the substance of VAT. Rates, the moment a tax obligation arises, and what belongs on an invoice stay where they were. If a vendor sells KSeF support as a rewrite of your accounting, be suspicious. If a vendor sells it as a checkbox, be more suspicious.

Polish invoicing tools have had the longest to get this right: compare ifirma, Fakturownia and enova365 on the checklist above rather than on price alone.