Since 1 April 2026 all businesses issue invoices in KSeF. Until the end of the year there is a penalty-free period — the last chance to fine-tune your invoicing calmly.
The National e-Invoicing System (KSeF) is now mandatory. Since 1 February 2026 all businesses receive invoices in KSeF, and since 1 April 2026 the remaining businesses — companies and sole traders, regardless of their VAT status — also issue invoices in the system.
Key dates
- 31 December 2026 — end of the period without financial penalties for KSeF-related errors.
- 1 January 2027 — the obligation to issue invoices in KSeF extends to the smallest businesses (sales documented by invoices of up to PLN 10,000 gross per month).
- 1 January 2027 — the KSeF invoice number must be quoted in transfers between VAT payers.
What to check now
- Whether your invoicing software sends invoices to KSeF automatically.
- Who in your business has permissions to issue and receive invoices in the system.
- How you issue invoices in emergency mode when KSeF is unavailable.
- Whether corrective and advance invoices quote the KSeF number of the original invoice.
The penalty-free period is a good time to make corrections — from January, mistakes will start to cost money. If you're not sure everything works as it should, we'll carry out a short audit of invoicing in your business.
