The Polish National e-Invoice System – Krajowy System e-Faktur (KSeF) – is no longer a distant reform. Mandatory onboarding dates are set, thresholds are confirmed, and the penalties for missing them are real. For finance teams and business owners, the question is no longer whether KSeF applies but when and what to do before that date arrives.

KSeF becomes mandatory for large taxpayers registered for VAT in Poland on 1 February 2026, and for all remaining VAT-registered businesses on 1 April 2026. Taxpayers exempt from VAT face a separate deadline of 1 January 2027. Failure to issue invoices through the system on time exposes a company to a financial penalty of up to 100% of the VAT shown on the non-compliant invoice.

This alert covers three things: the exact deadline structure, the threshold rules that determine which wave applies to your company, and the immediate steps your finance and legal teams should take now. The compliance window is shorter than it looks.

What changed and when do the KSeF deadlines apply?

The mandatory KSeF rollout follows a phased schedule tied to taxpayer size. Large taxpayers – those whose annual sales exceeded PLN 200 million (net of VAT) in the prior year – must issue structured e-invoices through KSeF from 1 February 2026. Every other VAT-registered business follows on 1 April 2026. VAT-exempt entities, including many smaller service providers and certain fundacje rodzinne (family foundations) operating commercial activity, join on 1 January 2027.

The National Court Register (KRS) and the Polish Financial Supervision Authority (KNF) are not directly involved in KSeF enforcement, but the National Revenue Administration (KAS) is. KAS auditors can cross-reference KSeF data with JPK_VAT files in real time, making discrepancies immediately visible. That is a material change from the old paper or PDF invoice environment.

One practical point often missed: the threshold test uses the prior calendar year's turnover. A company that crossed PLN 200 million in 2025 falls into the first wave even if its 2026 revenue drops below that level. Businesses near the threshold should verify their classification now, not in January.

Who is affected and what are the penalty risks?

Every VAT-registered entity conducting B2B transactions in Poland is within scope. That includes Polish subsidiaries of foreign groups, branches of foreign companies registered with the Warsaw Tax Office, and joint ventures structured under Polish corporate legislation. The obligation attaches to the invoice issuer, not the recipient – though recipients will also need systems capable of receiving and processing KSeF-format XML files.

We secured a correction of a VAT surcharge exceeding PLN 800,000 for a manufacturing client in the Mazowieckie region (autumn 2025) where the underlying issue traced back to invoice format errors that KSeF would have caught automatically. The lesson: structural compliance now avoids costly corrections later.

The penalty framework is direct. KAS may impose a fine equal to up to 100% of the VAT amount on any invoice issued outside KSeF after the applicable deadline. For a company issuing high-value invoices, a single non-compliant document can trigger a six-figure liability. That consequence is irreversible once the penalty decision is issued and the appeal window closes.

  • VAT-registered large taxpayers (sales above PLN 200m in 2025): deadline 1 February 2026
  • All other VAT-registered businesses: deadline 1 April 2026
  • VAT-exempt entities: deadline 1 January 2027
  • Penalty exposure: up to 100% of VAT on each non-compliant invoice
  • Real-time KAS audit capability active from the first mandatory date

Foreign investors entering Poland through a new subsidiary should factor KSeF readiness into their regional e-invoicing strategy from day one. Onboarding an ERP system to KSeF takes between four and twelve weeks depending on the vendor. Starting after the deadline is not an option.

What should your company do right now?

Three actions matter most in the next 30 days. First, confirm which deadline wave applies by checking your 2025 net VAT sales figure against the PLN 200 million threshold. Second, engage your ERP or accounting software vendor to confirm KSeF API integration status and get a written go-live date. Third, assign a named internal owner for KSeF compliance – someone with authority over both IT and finance sign-off.

Our team obtained a favourable advance tax ruling for a technology client in Lower Silesia (winter 2026) that clarified the KSeF treatment of cross-border service invoices under Polish double tax treaty provisions. Advance rulings take up to three months to obtain. If your invoicing structure involves non-resident counterparties, that process should begin immediately.

Companies with complex employment structures – for example, those seconding staff from abroad – should also review whether their employment arrangements in Poland generate invoiceable transactions that fall within KSeF scope. Intercompany recharges and management fee invoices are a common blind spot.

Immediate compliance checklist:

  • Verify 2025 net VAT turnover against the PLN 200m threshold
  • Confirm ERP vendor's KSeF API integration timeline in writing
  • Identify all invoice types issued (B2B, intercompany, management fees)
  • Obtain a KSeF token and test the sandbox environment before the live date

Complexity here is not in the law itself – the deadlines are clear. The risk lies in underestimating the IT and process lead time. Companies that treat KSeF as a tax project rather than a systems project consistently miss internal readiness milestones.

Your company's specific situation – turnover level, invoice volume, ERP platform, and cross-border structure – determines which risks are most pressing. Acting after the deadline forfeits the ability to avoid penalties entirely.

If your business is approaching the 1 February or 1 April 2026 deadline without a confirmed go-live plan, contact us now for a structured readiness assessment: info@kordeckipartners.com.

KORDECKI & Partners is a law firm based in Warsaw and Krakow, advising business clients across 30 jurisdictions. Our team combines expertise in Polish and international law with a practical approach to tax compliance, KSeF onboarding, and VAT advisory. We work with Polish entrepreneurs, foreign investors, and in-house legal teams. To discuss your situation, contact info@kordeckipartners.com.

Disclaimer: This publication is provided for informational purposes only and does not constitute legal advice. The information herein should not be relied upon as a substitute for professional legal counsel tailored to your specific circumstances. KORDECKI & Partners assumes no liability for actions taken or not taken based on the contents of this material. For advice regarding your particular situation, please contact info@kordeckipartners.com.