A Budapest-based manufacturing company invoices its Polish subsidiary weekly. From 1 February 2026, every one of those invoices must pass through Poland's National e-Invoicing System – Krajowy System e-Faktur (KSeF) – or the Polish entity faces financial penalties. The obligation is not optional, and the grace period for large taxpayers has already closed. Hungarian companies with Polish VAT registrations are now inside the mandatory regime.

Poland's mandatory KSeF regime entered force on 1 February 2026 for taxpayers whose 2024 turnover exceeded PLN 200 million. All remaining VAT-registered entities – including foreign companies registered for Polish VAT – join the system on 1 April 2026. Failure to issue structured invoices through KSeF exposes the issuer to a financial penalty of up to 100% of the VAT shown on the non-compliant invoice. The obligation applies regardless of where the issuing company is incorporated.

This alert sets out the two-phase rollout, identifies which Hungarian businesses are caught, and lists the immediate steps required before 1 April 2026. It also flags the 2027 extension that affects invoices issued to consumers and cross-border scenarios outside standard Polish VAT registration.

What changed in Polish tax law – and when?

Poland's KSeF framework was introduced under Polish tax legislation governing structured invoicing. The Ministry of Finance confirmed the revised timeline in mid-2024 after an earlier planned date was postponed. The National Court Register (KRS) and the Polish Financial Supervision Authority (KNF) are not directly involved in KSeF compliance, but the National Revenue Administration (KAS) – Krajowa Administracja Skarbowa – enforces the obligation and conducts audits. KAS has already issued guidance confirming that foreign entities with a Polish VAT number are treated identically to domestic taxpayers for KSeF purposes.

The rollout has two hard deadlines. First: 1 February 2026, for taxpayers whose gross sales in 2024 exceeded PLN 200 million. Second: 1 April 2026, for all other VAT-registered entities. A third phase, covering invoices to private individuals (faktury B2C) and certain cross-border transactions, is scheduled for 1 January 2027. Missing either of the first two dates is not a technical irregularity – it triggers the penalty regime immediately.

One detail catches many foreign advisors off guard. The PLN 200 million threshold is measured against the Polish VAT registration, not the global group turnover. A Hungarian company with modest Polish revenues may still fall into the April 2026 wave rather than the February wave. That distinction matters for planning, but not for the ultimate obligation: both groups must comply.

Which Hungarian companies are affected?

Any Hungarian entity holding a Polish VAT number – whether through a branch, a fixed establishment, or a standalone registration – is inside the KSeF obligation from 1 April 2026. The trigger is the Polish VAT number itself. Hungarian companies that sell goods or services in Poland under the distance-selling rules, those with a fiscal representative in Poland, and those registered following an intra-Community acquisition all qualify. There is no exemption based on the company's country of incorporation.

Three categories of Hungarian business face the most immediate exposure. First, manufacturers and distributors supplying Polish customers on a B2B basis – these companies issue the highest volume of invoices and face the greatest operational disruption. Second, IT and service providers billing Polish entities for ongoing contracts – structured invoices must be generated in the XML FA(2) schema and submitted in real time. Third, Hungarian holding companies that invoice Polish subsidiaries for management fees or transfer pricing-related services – every intercompany charge becomes a KSeF-regulated document.

We secured a correction of a structured-invoice configuration error for a manufacturing client in the Mazowieckie region (autumn 2025), preventing a penalty exposure exceeding PLN 800,000. The error arose because the client's ERP system generated invoices in a legacy XML format that KAS did not accept. Early testing – at least 60 days before the go-live date – is the single most effective risk-reduction measure available.

Hungarian companies operating under the double tax treaty between Poland and Hungary should also review whether their Polish activities create a permanent establishment. A permanent establishment triggers full Polish tax registration, which in turn triggers KSeF obligations independently of any VAT registration.

What must Hungarian companies do before 1 April 2026?

The compliance window is narrow. Companies that have not yet begun KSeF onboarding are already behind the recommended preparation schedule. The Ministry of Finance's own guidance suggests a minimum of 90 days for system integration – which, measured from 1 April 2026, places the start of technical work in early January 2026 at the latest. For companies reading this alert after that date, the priority shifts from orderly preparation to urgent remediation.

Immediate action items, in order of priority:

  • Confirm whether the Hungarian entity holds a Polish VAT number and identify the relevant threshold (PLN 200m for February 2026; all others for April 2026).
  • Obtain or verify KSeF access credentials through the Ministry of Finance's e-invoicing portal – the authorisation process alone can take up to 14 days.
  • Audit the company's invoicing software for FA(2) schema compatibility and submit at least one test invoice before the go-live date.
  • Review all intercompany invoices – management fees, IP licensing, and transfer pricing charges – to confirm they fall within the structured invoice requirement.
  • Appoint a Polish tax advisor with KSeF onboarding experience to manage KAS correspondence and any penalty mitigation filings.

Our team assisted a Hungarian investor's Polish subsidiary in Lower Silesia (spring 2026) in completing emergency KSeF registration and system integration within 18 days, avoiding penalties that would have applied from the first non-compliant invoice. Speed matters, but accuracy matters more – a misconfigured integration can generate hundreds of invalid invoices before the error is detected.

For context on broader Polish-Hungarian business structures, the cross-border insolvency framework between Poland and Hungary illustrates how Polish regulatory obligations extend to foreign-incorporated entities in ways that Hungarian counsel may not anticipate.

The 2027 phase – covering B2C invoices and certain export transactions – requires separate preparation. Companies that complete their April 2026 integration correctly will find the 2027 extension manageable. Those that rush the initial onboarding risk compounding errors across both phases. For a full picture of Polish tax obligations relevant to your structure, see our Polish tax practice overview.

Specific situations require tailored advice. A Hungarian company with a Polish VAT number, intercompany invoicing, and a potential permanent establishment faces overlapping obligations under KSeF, Polish corporate income tax law, and transfer pricing rules. Each layer carries its own penalty regime. Addressing them in isolation – rather than as a single compliance project – forfeits the efficiency gains available from a coordinated approach and leaves residual exposure in each area.

To receive an expert assessment of your company's KSeF readiness and Polish tax exposure, contact info@kordeckipartners.com.

Frequently asked questions

Q: Does KSeF apply to a Hungarian company that only occasionally invoices Polish customers?

A: Yes, if the Hungarian company holds a Polish VAT number. The obligation is tied to VAT registration, not invoice frequency or volume. Even a single invoice issued after 1 April 2026 outside the KSeF system exposes the issuer to a penalty of up to 100% of the VAT on that invoice. Companies that invoice Polish customers infrequently should consider whether their Polish VAT registration remains necessary – but deregistration must be completed before the mandatory date to avoid the obligation.

Q: How long does KSeF technical integration typically take?

A: The Ministry of Finance recommends 90 days for full ERP integration. In practice, companies with modern invoicing systems have completed integration in 30 to 45 days when a dedicated technical team is assigned from day one. The authorisation process with the Ministry of Finance portal takes up to 14 days and must be completed before any test invoices can be submitted. Starting after 1 February 2026 for the April deadline leaves very limited margin for errors.

Q: Does KSeF affect IP Box or family foundation structures involving Polish entities?

A: KSeF governs the form of invoicing, not the underlying tax regime. A Polish entity benefiting from IP Box relief or a fundacja rodzinna (family foundation) that issues B2B invoices must still comply with KSeF from the applicable deadline. The structured invoice requirement applies to the invoicing entity regardless of its tax treatment. A tax advisor Warsaw-based or otherwise familiar with Polish tax law should review whether the entity's invoicing volume and counterparty profile require any structural adjustments before the deadline.

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 KSeF onboarding, VAT compliance, and cross-border tax structuring. 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.