The National e-Invoice System (KSeF) is changing the way invoicing works in Poland. This guide covers everything you need to do so the 1 July 2026 deadline does not catch you off guard.
An invoice issued outside KSeF has no legal validity (with limited exceptions).
Cancellation is impossible — only corrections through KSeF.
Full transaction visibility for the Tax Authority — end of off-the-books invoices.
Elimination of paper invoices in B2B trade.
The National e-Invoice System (KSeF — Krajowy System e-Faktur) is the Polish Ministry of Finance's central platform for issuing, receiving, and storing structured invoices (XML format — FA(2) schema). Every B2B invoice passes through the MF server, receives a unique KSeF number, and is stored there for 10 years.
Key consequences:
2. Who is obligated
From 1 July 2026
All active VAT payers
Sole traders (JDG), limited companies (sp. z o.o.), partnerships
Foreign entities with a fixed place of business in Poland
From 1 January 2027
VAT-exempt taxpayers (flat-rate, small businesses)
Cost invoices from consumers
Who is NOT covered: B2C invoices (for consumers) — can still be issued traditionally. Voluntary use is allowed.
3. 2026 Timeline — implementation calendar
By 31 March 2026 — deadline to select a KSeF provider and sign a contract.
By 31 May 2026 — final testing, generating tokens, team training.
1 July 2026 — obligation starts. First day of issuing invoices only through KSeF.
By 31 July 2026 — first VAT settlement with KSeF invoices (JPK_V7M).
4. How to prepare — checklist
Audit your current invoicing process — which systems issue invoices, who approves them, what integrations are in use.
Choose a KSeF provider — if you use Comarch, wFirma, iFirma or Subiekt, check their readiness. If you have custom ERP, you need an integrator.
Generate tokens — for every person authorised to issue invoices.
Emergency procedure — written instructions for when KSeF is unavailable.
Team training — minimum 2 hours for every invoice-issuing staff member.
Testing — issue test invoices for 2–3 weeks before go-live.
5. KSeF authorisation token
The token expires after 1 year — remember to renew it!
A token generated by the CEO does not work for the accountant unless she has the relevant permissions.
The token is sensitive data — never send it by email or Slack.
The KSeF token is a unique string that identifies the company in the system. It is generated in the MF panel via Profil Zaufany (Trusted Profile) or a qualified electronic signature.
Most common mistakes:
6. Corrective invoices in KSeF
A correction issued through KSeF does not require the buyer's acceptance — it is deemed delivered at the moment the KSeF number is assigned. This significantly simplifies document flow and speeds up bookkeeping.
Three types of corrections: data change, value change, cancellation (zeroing).
7. Outages and offline mode
An offline invoice has the issuance date from the moment it was created.
You must upload it to KSeF within 14 days of the outage ending.
The KSeF number is assigned only after the offline invoice is accepted.
The MF has provided an offline (emergency) mode for situations where the KSeF system is unavailable or your company has no internet access:
8. Penalties for failing to implement KSeF
Issuing an invoice outside KSeF (when obligatory): penalty up to 100% of the VAT amount on the invoice.
Failure to meet statutory issuance deadlines: criminal fine.
Loss of the right to deduct VAT by the buyer from an invoice issued in violation of KSeF.
9. Frequently asked questions
When does KSeF become mandatory?
From 1 July 2026 for all active VAT taxpayers. For VAT-exempt taxpayers the obligation starts on 1 January 2027.
Are invoices issued outside KSeF invalid?
Yes. After 1 July 2026 an invoice issued outside KSeF (except B2C and outages) is treated as not issued, which means the buyer loses the right to deduct VAT.
What about invoices for natural persons (B2C)?
Invoices for consumers can still be issued traditionally — KSeF is optional for B2C.
How long does it take to get a KSeF number?
The system assigns a KSeF number immediately (within seconds). The issue date = send date; the receipt date for the buyer = the date the KSeF number was assigned.
What if the system goes down mid-month?
An offline mode is provided — you can issue invoices offline (for up to 14 days) and submit them to KSeF once it is restored.
Do I need special software?
Yes — your ERP/accounting programme must have KSeF integration. Most popular systems (Comarch, wFirma, iFirma, Subiekt) already do.
How much does KSeF implementation with Danexis cost?
For our accounting clients — implementation and training FREE. For external companies — from PLN 800 net for the full package (token + integration + team training).