A Romanian company with Polish operations receives an invoice from its Warsaw-based supplier. The document arrives not by email, but through a government platform. No platform access, no valid invoice – and no right to deduct input VAT. That is the practical reality of Poland's National e-Invoicing System, known as Krajowy System e-Faktur (KSeF), which becomes mandatory for all VAT-registered businesses in Poland from 1 February 2026.

KSeF is Poland's structured electronic invoicing system, operated by the National Revenue Administration (Krajowa Administracja Skarbowa, KAS). From 1 February 2026, every VAT-registered entity conducting taxable transactions in Poland must issue and receive invoices exclusively through the KSeF platform. Romanian businesses with Polish subsidiaries, branches, or regular B2B trade relationships are directly affected. Failure to comply risks loss of input VAT deduction rights and exposure to penalties reaching PLN 100 per non-compliant invoice.

This alert covers three things: what KSeF requires, which Romanian businesses are affected and when, and the steps you should take before the February 2026 deadline. The window for preparation is narrowing.

What has changed under KSeF and who is affected?

KSeF replaces paper and PDF invoices with a single, state-controlled XML format called FA(2). Every invoice issued to a Polish VAT counterparty must be submitted to the KSeF platform, assigned a unique identification number, and only then treated as legally issued. The National Revenue Administration (KAS) stores each invoice and makes it available to both parties in real time. The Polish Financial Supervision Authority (Komisja Nadzoru Finansowego, KNF) does not regulate KSeF directly, but financial institutions operating in Poland must align their internal processes with the new format.

Romanian businesses fall into two main categories. First, companies with a Polish VAT registration – whether through a subsidiary, branch, or fixed establishment – must comply from 1 February 2026. Second, Romanian entities that sell goods or services to Polish customers and issue Polish VAT invoices are also within scope. The threshold question is simple: if you have a Polish VAT number, KSeF applies to you.

One common misconception is that KSeF affects only Polish companies. It does not. Any entity – regardless of country of incorporation – that holds a Polish VAT registration is bound by the obligation. Romanian holding companies with Polish operating subsidiaries registered for VAT in Poland must ensure their ERP systems can generate and transmit FA(2) XML files. That is not a minor IT adjustment; it typically requires 8 to 12 weeks of integration work.

  • Polish VAT registration triggers full KSeF compliance from 1 February 2026
  • Invoices not issued through KSeF are treated as not issued under Polish tax law
  • Input VAT deduction is blocked on non-compliant purchase invoices
  • Penalties reach PLN 100 per invoice for systematic non-compliance
  • B2C transactions and certain cross-border supplies carry limited exemptions

We helped a manufacturing client in the Mazowieckie region complete KSeF integration and staff training within a 10-week window (autumn 2025). Starting the process late forced compressed timelines and higher implementation costs. Early movers avoid that pressure entirely.

What should Romanian businesses do before 1 February 2026?

The immediate priority is a compliance gap analysis. Romanian businesses should map every Polish VAT transaction – sales, purchases, intra-group supplies – and identify which document flows require KSeF integration. Under Polish tax law, the obligation to issue through KSeF applies to the seller. However, the buyer's right to deduct input VAT depends on receiving a KSeF-compliant invoice. Both sides of the transaction carry risk.

Practical preparation involves four parallel workstreams. ERP or accounting software must be updated to produce FA(2) XML. API or batch-upload connectivity to the KSeF platform must be tested. Staff handling Polish invoicing need procedural training. And internal controls must be updated to flag any invoice that bypasses the platform. For guidance on how KAS audits assess invoicing compliance, see our detailed overview of KAS tax audit procedures and preparation steps.

Romanian businesses with intra-group transactions should also review their transfer pricing safe harbour positions under Polish law. KSeF creates a complete audit trail of every intra-group invoice. KAS will be able to cross-reference declared transfer prices against actual invoiced amounts with far greater speed than before. Discrepancies that previously took years to surface in an audit may now be flagged within months.

What to prepare before 1 February 2026:

  • Confirm which Polish VAT registrations your group holds
  • Obtain KSeF authentication credentials from KAS for each registration
  • Test FA(2) XML generation in your ERP or accounting system
  • Run end-to-end platform connectivity tests with at least one live transaction

For Romanian businesses active in technology or IP-intensive sectors in Poland, KSeF intersects with other compliance obligations. Our IP and technology practice for Romanian clients addresses how structured invoicing affects IP Box and R&D cost documentation under Polish tax law. A family foundation holding Polish IP assets, for instance, must ensure that royalty invoices flow through KSeF from the mandatory date.

We assisted a Romanian IT services provider in mapping its Polish intra-group invoice flows and completing KSeF onboarding for two Polish entities (spring 2025, Silesia region). The process identified a transfer pricing documentation gap that would have been exposed in the first post-KSeF KAS review.

Specific situations – such as a Polish tax advisor Warsaw engagement, IP Box claims, or cross-border supply chains involving Polish tax law – require tailored analysis. The KSeF obligation does not pause for businesses still working through their compliance programmes.

To discuss how KSeF applies to your Romanian business's Polish operations, email info@kordeckipartners.com. We will map your exposure, identify the integration steps required, and coordinate with your ERP team to meet the 1 February 2026 deadline.

Frequently asked questions

Q: Does KSeF apply to a Romanian company that only occasionally sells to Polish customers?

A: Yes, if that company holds a Polish VAT registration. The frequency of transactions does not affect the obligation. Any entity with a Polish VAT number must issue invoices through KSeF from 1 February 2026. Occasional sellers with no Polish VAT registration and no fixed establishment in Poland generally fall outside the mandatory scope, though they should verify their status with a tax advisor.

Q: How long does KSeF integration typically take, and what does it cost?

A: Integration timelines depend on the ERP system in use. Standard SAP or Oracle environments typically require 8 to 12 weeks of technical work. Smaller accounting platforms may be updated faster if the software vendor has already released a KSeF module. Costs vary widely – from a few thousand PLN for a plug-in update to six-figure sums for custom API development. Starting the process in November or December 2025 leaves no buffer for delays.

Q: Is it true that KSeF does not apply to B2C invoices?

A: Partly. Business-to-consumer transactions are currently excluded from the mandatory KSeF scope. However, if a Romanian business issues invoices to both Polish businesses and Polish consumers, it must implement KSeF for the B2B portion regardless. Mixed-flow businesses should not assume a B2C exemption covers their entire Polish invoicing activity. Each transaction type must be assessed separately under Polish tax law.

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 cross-border 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.