KSeF Poland 2026: The Complete Guide to Mandatory E-Invoicing

Poland has joined the growing list of EU countries with mandatory e-invoicing — and KSeF (Krajowy System e-Faktur, or the National e-Invoicing System) is the system every Polish business now has to use.

Unlike Germany's decentralised approach or France's PDP-network model, Poland chose the most centralised option possible: every invoice must pass through a government platform and receive a unique reference number before it has any legal standing for VAT purposes.

This guide covers the full picture: what KSeF actually is, who must use it, what the FA_VAT format looks like, the exact deadlines, and what to do if you're reading this having missed the February 2026 date for large businesses.

What Is KSeF?

KSeF — Krajowy System e-Faktur — is a centralised government clearing platform for electronic invoices. Built and operated by the Ministerstwo Finansów (Ministry of Finance), it works like this:

Your accounting software generates a structured FA_VAT XML invoice
The invoice is sent to the KSeF platform via the official API (or the web portal for low volumes)
KSeF validates the invoice against the FA_VAT schema and your business's NIP (tax identification number)
If valid, KSeF assigns a unique KSeF reference number (numer referencyjny KSeF) and timestamps the invoice
The invoice is now legally valid for VAT purposes
The buyer retrieves the invoice from KSeF using the reference number

This is fundamentally different from Germany or France, where invoices go directly between sender and receiver and only the format needs to be compliant. In Poland, the government sits in the middle of every transaction.

Why the Government Sits in the Middle

The reason is VAT gap reduction. Poland has one of the EU's more aggressive approaches to closing the VAT gap (the difference between expected and actually collected VAT). With every invoice passing through KSeF in real time, the tax authority has near-complete visibility into every B2B transaction. Cross-referencing what businesses report on their JPK_VAT declarations against actual invoice data becomes trivial.

For businesses, this is more friction in the short term but comes with genuine benefits: less risk of fraudulent invoices, simpler audits, and eventual elimination of the separate JPK_FA (invoice reporting) obligation.

The Timeline: What Happened and When

Poland's KSeF journey has been rocky. Here's the honest history:

January 2021 — KSeF launches as voluntary The system goes live, but participation is optional. Early adopters gain the benefit of buyers being able to claim VAT immediately without the usual 30-day delay — a real financial incentive.

July 2024 (original mandatory date) — postponed After a Ministry-commissioned cybersecurity audit found critical vulnerabilities in the KSeF platform, the Ministry announced in January 2024 that the July 2024 mandatory date would not proceed. This was a significant public failure and forced a complete security overhaul.

September 2025 — amended KSeF Act passed With remediation complete, the Polish parliament enacted amendments setting a new mandatory timeline:

Date	Who	Requirement
1 February 2026	Large taxpayers (>PLN 200M annual turnover)	Mandatory KSeF for all B2B VAT invoices
1 April 2026	All other VAT-registered businesses	Mandatory KSeF for all B2B VAT invoices

1 February 2026 — mandate live for large taxpayers Large businesses with annual turnover exceeding PLN 200 million began issuing all domestic B2B invoices exclusively through KSeF.

1 April 2026 — full mandate All remaining VAT-registered businesses in Poland must now use KSeF for every domestic B2B invoice.

Who Must Use KSeF?

The mandate applies to every entity registered for VAT in Poland that issues domestic B2B invoices. This includes:

Polish companies of all sizes (sp. z o.o., S.A., spółki osobowe)
Sole traders (jednoosobowa działalność gospodarcza) registered for VAT
Foreign companies with a Polish NIP/VAT number
Tax groups (VAT groups — podatkowe grupy kapitałowe)

What Is Out of Scope?

B2C invoices — invoices to private consumers not registered for VAT
Cross-border invoices — export to non-Polish buyers (though these must still be reported separately)
Intra-EU B2B invoices to customers in other EU member states
Invoices from non-VAT-registered entities (zwolnienie podmiotowe — those below the PLN 200,000/year threshold who chose not to register)
Tickets, parking receipts, simplified invoices for transactions under PLN 450 (€100) in some circumstances

There is also a special offline mode provision: if the KSeF platform is unavailable (an API outage), businesses may issue invoices in an offline KSeF mode using FA_VAT XML and upload them once the platform recovers within the allowed window. Your software must support this fallback.

The FA_VAT Format: What It Actually Is

Every KSeF invoice uses the FA_VAT schema — an XML format published and maintained by the Ministerstwo Finansów. The current schema version is FA(2), which has been required since the voluntary phase and is the only version accepted under the 2026 mandate.

Key characteristics of FA_VAT:

Pure XML (no PDF component — unlike Germany's ZUGFeRD or France's Factur-X)
Based on the Polish tax authority's own schema (not a direct implementation of EN 16931, though structurally influenced by it)
Contains the sender's NIP, buyer's NIP, invoice amount, VAT breakdown, payment terms, and other mandatory fields
Submitted via API using certificate-based authentication (or a signed EPUAP/trusted profile for manual submission)

The full FA(2) XSD schema is published at: https://www.podatki.gov.pl/ksef/

Does FA_VAT Comply with the EU's EN 16931?

This is an important nuance. FA_VAT is not natively EN 16931 compliant — it is a Polish-specific schema. However, the Polish government has published a mapping between FA_VAT and EN 16931 to facilitate interoperability for cross-border scenarios where the counterparty requires an EN 16931 format. For purely domestic Polish B2B invoicing, EN 16931 compliance is not required — FA_VAT through KSeF is the legal standard.

KSeF Authentication: How to Connect

Connecting to KSeF requires authentication. Businesses can use one of three methods:

Qualified electronic seal / signature (pieczęć elektroniczna / podpis kwalifikowany) — the standard method for businesses. A qualified certificate issued by a Polish trust service provider (e.g., Certum, EuroCert, Sigillum).
Trusted Profile (Profil Zaufany) — a government-issued digital identity. Practical for sole traders submitting low volumes manually through the KSeF portal.
API token — for software integration. A token is generated by authenticating with one of the above methods and can then be used programmatically for batch submissions.

In practice, if you're using accounting software (Comarch, InsERT, enova365 etc.), the software handles authentication for you once you configure your certificate or token in its settings.

What Penalties Apply for Non-Compliance?

The KSeF Act specifies meaningful financial penalties:

Up to 100% of VAT shown on the invoice if an invoice is issued outside KSeF when the mandate applies (i.e., you issue a PDF or paper invoice instead of going through KSeF)
Buyers who receive and book a non-KSeF invoice risk having their VAT deduction disallowed — this creates pressure from buyers on sellers to comply
The tax authority may also initiate broader VAT audits if KSeF non-compliance is detected

During the initial transition period (February–June 2026), penalties were announced to be applied with some discretion for first-time technical failures, but the Ministry has stated that deliberate evasion will be pursued.

The KSeF Offline Mode: What Happens When the System Goes Down

The 2024 cybersecurity failure was a wake-up call, and the amended KSeF Act specifically addresses platform availability. The rules for offline mode are:

If the KSeF API is unavailable, you may issue invoices in offline KSeF format — an FA_VAT XML file with a locally generated temporary identifier
These offline invoices must be uploaded to KSeF within 1 business day of the platform becoming available again
Your accounting software must be able to detect the KSeF outage and switch to offline mode automatically

This is not a loophole — it is a safety mechanism. You cannot choose to stay offline. Any good KSeF-compliant software (Comarch, InsERT, enova365) handles this automatically.

Practical Checklist: Getting Compliant

If You Are a Large Business (Already Mandatory)

☑ Your accounting software must be KSeF-integrated with FA(2) schema support
☑ Your IT or finance team must have a valid qualified electronic certificate configured
☑ All purchase invoices from KSeF-eligible suppliers must be retrieved from KSeF (not accepted as PDFs)
☑ Your ERP must handle KSeF reference numbers — storing them, printing them on payment reminders, and matching them in accounts payable
☑ Staff must understand the offline mode procedure

If You Are a Small Business (Mandatory from 1 April 2026)

Update your accounting software — most Polish tools had free updates for KSeF. If your software is not KSeF-ready, switch now
Register with KSeF: log in to https://www.podatki.gov.pl/ksef/ with your Trusted Profile or qualified certificate
Issue a test invoice in the KSeF test environment (środowisko testowe) before going live
Confirm your invoice template includes the mandatory KSeF-required fields (buyer's NIP, correct VAT breakdown structure)
Inform your clients and suppliers that you are now KSeF-mandated

Frequently Asked Questions

Q: Can I still send a PDF invoice to my client? A: No — not for domestic B2B transactions once the mandate applies to you. The PDF has no legal standing as a VAT invoice. Your client cannot claim VAT on a PDF they receive from you. You must issue through KSeF.

Q: Does KSeF replace JPK_VAT reporting? A: Not yet fully. JPK_VAT (SAF-T reporting) remains a separate obligation. However, the Ministry has indicated that JPK_FA (the separate invoice reporting) will eventually be eliminated since KSeF provides equivalent data. Expect further simplification in 2027–2028.

Q: What if my accounting software is not KSeF-ready? A: Switch software. The major Polish platforms (Comarch, InsERT, enova365, WAPRO, Symfonia) all support KSeF. If you're using an international ERP (SAP, Oracle, Microsoft Dynamics), check with your vendor — most have released KSeF connectors or modules.

Q: What about invoices in a foreign currency? A: KSeF handles multi-currency invoices. The FA_VAT schema includes fields for both the invoice currency and the PLN equivalent (required for VAT calculation). Your software handles the conversion.

Q: My client is a foreign company. Do I use KSeF? A: If the transaction is subject to Polish VAT (e.g., services provided in Poland), you generally do still need to issue through KSeF, even for foreign buyers. For export of goods (zero-rated), different rules apply. Consult your tax advisor for cross-border edge cases.

Last updated: April 2026. KSeF regulations are actively evolving — check podatki.gov.pl for the latest schema and regulatory updates.