Guide
E-invoicing in Poland: KSeF and FA(3)
Poland’s KSeF explained: rollout stages, the FA(3) invoice structure, access permissions and evidence to retain after submitting an invoice file.
KSeF is an invoicing system, not merely a format selected from a dropdown. Working with a Polish customer requires understanding the mandate’s scope, the issuer’s permissions and the document that the software actually submits. A PDF sent by email does not demonstrate that an invoice entered KSeF.
Prepare FA(3) and access rights
The official documentation identifies FA(3) as the structure used by KSeF 2.0. Ask your provider to confirm the supported version and demonstrate a complete transaction in the test environment. Check the permissions granted to the person or service sending and receiving invoices. Successful authentication does not establish that the account has every permission required for that particular business. Document who can renew credentials and who investigates a failed submission.
Retain usable evidence
Link the commercial invoice number to the reference assigned by the system and to the responses received. Plan reconciliation between exported documents and documents actually accepted. For offline procedures or an outage, follow the corresponding KSeF documentation rather than inventing a deadline. KlarFakt does not validate FA(3) or submit invoices to KSeF. Its EN 16931 checks cannot replace Poland’s national checks.
Position checked on 6 October 2026
KSeF is phased in: large businesses in February 2026, others in April. A temporary exemption through 2026 depends on a monthly PLN 10,000 invoiced-sales threshold.
Follow one invoice through to receipt
Start with one representative test invoice and the delivery channel agreed with its recipient. Record separately whether the file passed technical checks, whether transmission was accepted and whether the customer matched it to the underlying transaction. These are three different outcomes. Assign an owner to each failure and retain the original file alongside the responses. Also try a correction and a resend so that the process cannot silently create duplicate entries. A successful local validation report replaces neither a required transmission service nor an assessment of the transaction’s tax treatment. The linked country profile records the reviewed scope and unresolved points.
Sources and next steps
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No legal advice. Dates and obligations follow the official publications cited in the text; where a date is not final, the text says so.