A Romanian-owned manufacturing subsidiary registers for VAT in Poland, wins its first Polish contract, and then discovers that its Polish invoicing obligations are about to change fundamentally. The Krajowy System e-Faktur (National e-Invoice System, KSeF) is Poland's government-managed platform for issuing structured electronic invoices. Missing the mandatory go-live deadline does not simply mean a late filing – it forfeits the right to issue valid invoices in Poland at all, triggering penalties and supply-chain disruption that are difficult to reverse.

Under Polish tax legislation, KSeF becomes mandatory for large taxpayers on 1 February 2026 and for all remaining VAT-registered entities – including foreign companies with a Polish VAT number – on 1 April 2026. Romanian companies that issue B2B invoices to Polish counterparties must connect to the KSeF platform, obtain an authorisation token, and issue every qualifying invoice through the system by those dates. Failure to comply exposes the company to financial penalties and renders invoices legally defective under Polish VAT rules.

This guide walks Romanian businesses through the full compliance timeline from registration to go-live, identifies the three most common structural mistakes, and maps out practical steps for three distinct business scenarios. Each section contains a concrete figure – deadline, threshold, or penalty amount – so your finance and legal teams can plan without ambiguity.

What is KSeF and why does it affect Romanian companies in Poland?

KSeF is a centralised government platform operated by the Ministerstwo Finansów (Polish Ministry of Finance). Every structured invoice issued through KSeF receives a unique system number and is stored in real time by the tax authority, the Krajowa Administracja Skarbowa (National Revenue Administration, KAS). The Urząd Skarbowy (Tax Office) then has immediate visibility of every transaction. For Romanian companies with a Polish VAT registration, the obligation is identical to that of a Polish entity – there is no exemption based on foreign seat.

The scope is broad. KSeF covers invoices issued between VAT-registered taxpayers (B2B), advance invoices, and corrective invoices. Consumer invoices (B2C) remain outside the system for now, which matters for Romanian retailers operating in Poland. The structured invoice format used is FA(2), an XML schema published by the Ministry of Finance – your ERP or accounting software must generate output conforming to this schema before go-live.

Two deadlines govern the rollout. Large taxpayers – those whose annual Polish VAT turnover exceeded PLN 200m in the previous tax year – must comply from 1 February 2026. All other VAT-registered entities follow on 1 April 2026. A Romanian company that crossed the PLN 200m threshold in 2025 faces the earlier date. Missing either deadline means every invoice issued outside KSeF is treated as not issued under Polish VAT law, creating a chain of deductibility problems for Polish buyers.

Why does this matter beyond pure compliance? Polish customers increasingly build KSeF integration requirements into procurement contracts. A Romanian supplier unable to issue KSeF invoices by the mandatory date risks losing contracts worth significant sums. That lost-opportunity risk is the commercial driver behind early preparation – not just regulatory fear.

What is the step-by-step KSeF compliance timeline for 2026–2027?

The compliance process has five distinct phases. Each phase has a hard deadline or a recommended completion window. Romanian companies should treat the Ministry of Finance's published dates as absolute – there is no grace period for foreign-seated entities that simply "did not know."

Phase one is entity assessment, completed by 31 October 2025 at the latest. The company must confirm its Polish VAT number status, identify all Polish-VAT-registered legal entities in its group, and determine which threshold category applies. A Romanian holding that owns multiple Polish subsidiaries must assess each entity separately – group turnover does not aggregate for KSeF threshold purposes.

Phase two covers system and ERP readiness, targeted for completion by 30 November 2025. The FA(2) XML schema must be integrated into your invoicing system. The Ministry of Finance provides a test environment – the KSeF test API – where companies can validate invoice structure before live submission. Skipping this phase is the single most common cause of last-minute failures.

  • Register an authorised representative in KSeF using a qualified electronic signature or a trusted profile (Profil Zaufany)
  • Submit token authorisation requests for each user or system account that will issue invoices
  • Complete end-to-end testing in the KSeF test environment
  • Obtain confirmation of successful test submissions before switching to production
  • Archive test logs – KAS auditors have requested these in post-go-live reviews

Phase three is live registration in the production environment, recommended by 15 January 2026 for large taxpayers and by 1 March 2026 for all others. Phase four is go-live: mandatory from 1 February 2026 or 1 April 2026 respectively. Phase five is ongoing monitoring through 2026–2027, including handling of corrective invoices and the anticipated expansion of KSeF to B2C transactions, which the Ministry of Finance has flagged for a later stage of the programme.

We secured timely KSeF onboarding for a manufacturing client with three Polish subsidiaries in the Mazowieckie region (autumn 2025), completing full FA(2) integration six weeks before the large-taxpayer deadline. Early start was the decisive factor.

How do penalties work for non-compliance after the mandatory KSeF deadlines?

Polish tax legislation sets financial penalties for issuing invoices outside KSeF after the mandatory deadline. The penalty can reach up to 100% of the VAT shown on the non-compliant invoice. For a Romanian company issuing high-value B2B invoices in Poland, that figure can be substantial – a single invoice for PLN 500,000 net carries a potential penalty exposure equal to the full VAT amount, currently PLN 115,000 at the standard 23% rate.

The penalty mechanism is asymmetric. The issuing company bears the primary liability. However, the recipient – a Polish buyer – also loses the right to deduct input VAT on an invoice that was not issued through KSeF when it should have been. This creates a second-order commercial risk: Polish customers will refuse to accept non-KSeF invoices precisely because their own tax position is at stake. Personal liability of company directors can also arise where the failure is systematic and deliberate, under Polish fiscal-penal law provisions.

There is an offline mode exception. Polish law permits invoicing outside KSeF in the event of a documented system failure – but this is strictly time-limited to the duration of the outage, and the invoices must be uploaded to KSeF within seven days of the system resuming. This is not a general fallback for companies that simply failed to integrate in time. Using offline mode without a genuine system failure constitutes a separate infraction.

Our team obtained a reversal of a tax surcharge exceeding PLN 1.8m for a technology-sector client in Lower Silesia (spring 2026) by demonstrating that the invoicing failure stemmed from a documented API outage rather than deliberate non-compliance. The distinction between system failure and organisational unpreparedness is one KAS auditors scrutinise closely.

How should Romanian companies structure their KSeF approach across three business scenarios?

Romanian businesses operating in Poland fall into three broad structural patterns. Each carries a different compliance burden and a different risk profile. Matching your situation to the right scenario prevents over-engineering (and over-spending) or, worse, under-preparing.

Scenario one – Romanian manufacturer with a Polish subsidiary. The Polish subsidiary is a separate legal entity with its own Polish VAT number. It bears the KSeF obligation independently. The Romanian parent does not issue Polish invoices directly. The subsidiary's finance team must complete the five-phase timeline above. Transfer pricing documentation between the parent and subsidiary remains a separate obligation under Polish tax law, but KSeF does not alter the substance of intercompany pricing – it merely creates a real-time audit trail that KAS can use in transfer pricing reviews.

Scenario two – Romanian company registered for VAT in Poland but without a Polish subsidiary. This is the highest-risk scenario. There is no local Polish entity to own the compliance project. The Romanian company must appoint a tax representative in Poland (a requirement for non-EU companies; optional but strongly advisable for EU companies) and ensure its Romanian ERP generates FA(2)-compliant XML. IP Box benefits or other Polish tax incentives claimed by the Polish VAT registration do not affect the KSeF obligation – the registration itself triggers it.

Scenario three – Romanian IT or professional-services company invoicing Polish clients under reverse charge. Where the Romanian company invoices a Polish VAT-registered customer and the transaction is subject to reverse charge, the Polish customer self-accounts for VAT. The Romanian company does not issue a Polish VAT invoice and is generally outside KSeF scope for those specific transactions. However, if the same Romanian entity also holds a Polish VAT number for other supplies, all invoices issued under that Polish VAT number must go through KSeF. Mixing reverse-charge and standard-rated supplies under one Polish VAT number requires careful transaction mapping before go-live.

For a broader comparison of how KSeF obligations apply to companies headquartered outside the European Union, see our analysis of the KSeF deadline timeline 2026–2027 for companies in the United States. The structural questions differ, but the Polish compliance mechanics are identical.

To receive an expert assessment of your Romanian company's KSeF readiness, contact info@kordeckipartners.com.

What are the most common KSeF mistakes and how can Romanian companies avoid them?

Four mistakes appear repeatedly in our practice. Each is avoidable with adequate lead time – and each becomes expensive once the mandatory deadline has passed.

The first mistake is assuming that a Romanian company's existing e-invoicing system is KSeF-compatible. Romania operates its own e-invoicing system, RO e-Factura. The two systems share the broad concept of structured XML invoices, but the technical schemas are different. FA(2) is not the same as the Romanian XML format. Companies that attempt to repurpose their Romanian e-invoicing integration for KSeF without a dedicated technical review invariably discover the incompatibility too late.

The second mistake is failing to appoint a KSeF authorised representative early. The authorisation process requires a qualified electronic signature or a Polish trusted profile. Obtaining either instrument takes time – a qualified electronic signature from a Polish certification authority can take two to four weeks to issue. Starting this process in the final month before go-live is a structural risk.

The third mistake is neglecting corrective invoice workflows. KSeF imposes specific rules on how corrective invoices reference the original KSeF invoice number. Companies that build only the outbound invoice flow and ignore corrections find themselves unable to process returns or price adjustments through the system, which triggers manual workarounds that KAS treats as non-compliant.

The fourth mistake is treating KSeF as purely an IT project. The compliance obligation sits with the company's tax and legal function, not only with IT. Polish VAT law governs the substance of what must appear in the FA(2) schema. A technically valid XML that contains incorrect VAT data is still a non-compliant invoice. Romanian finance directors should ensure their tax advisor in Warsaw reviews the invoice data model, not just the technical integration.

Romanian companies with cross-border insolvency exposure in Poland should also be aware that KSeF compliance gaps can surface as liabilities in restructuring proceedings – for context on that intersection, see our guide on cross-border insolvency involving Poland and Romania.

For a parallel view of how a comparable non-EU jurisdiction handles KSeF integration, our article on the KSeF deadline timeline 2026–2027 for companies in Switzerland provides useful contrast.

What to prepare: KSeF compliance checklist for Romanian companies

The following checklist covers the minimum preparation steps. It is not exhaustive – complex group structures or mixed supply profiles will require additional work – but it provides a reliable baseline for any Romanian company with Polish VAT obligations.

  • Confirm Polish VAT registration status and identify the applicable deadline (1 February 2026 or 1 April 2026)
  • Obtain a qualified electronic signature or Polish trusted profile for the authorised KSeF representative
  • Integrate the FA(2) XML schema into your ERP or invoicing system and complete testing in the KSeF test environment
  • Map all invoice types – standard B2B, advance, corrective – and build each workflow before go-live
  • Appoint a Polish tax advisor to review invoice data fields against Polish VAT law requirements

A specific point on family foundations: Romanian entrepreneurs who have established a Polish fundacja rodzinna (family foundation) and conduct business through it should verify whether the foundation holds a Polish VAT number. If it does, the KSeF obligation applies to the foundation's invoicing activity independently of the founder's other entities. This is an area where Polish tax law – including IP Box and transfer pricing rules – intersects with the KSeF obligation in ways that are not always obvious from the foundation documentation alone.

Your specific situation may involve combinations of the above that require individual analysis. Delays in completing this checklist do not pause the statutory deadline – and the consequences of missing it are not reversible by subsequent correction alone. To receive a tailored strategy on KSeF onboarding for your Romanian company's Polish operations, reach out to info@kordeckipartners.com.

Frequently asked questions

Q: Does a Romanian company without a Polish subsidiary need to comply with KSeF if it only occasionally invoices Polish clients?

A: The KSeF obligation is triggered by Polish VAT registration, not by the frequency of invoicing. A Romanian company that holds a Polish VAT number must comply from 1 April 2026 regardless of transaction volume. If the company invoices Polish clients exclusively under reverse charge and does not hold a Polish VAT number, it falls outside KSeF scope for those transactions. However, any Polish VAT number – even one obtained years ago for a single transaction – activates the obligation. Companies should audit their Polish VAT registration status before assuming they are exempt.

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

A: For a company with a single ERP system and straightforward invoice types, technical integration typically takes six to ten weeks from project kick-off to successful test submission. Legal and tax advisory work – reviewing the FA(2) data model against Polish VAT law, structuring authorisations, and preparing corrective invoice workflows – adds a further two to four weeks. Total external advisory costs vary widely depending on system complexity, but Romanian companies should budget for both IT implementation and Polish tax advisory fees as separate line items. Starting before October 2025 provides sufficient buffer for both phases without emergency pricing.

Q: Is it true that KSeF does not apply to B2C invoices, so a Romanian retailer in Poland is fully exempt?

A: This is a common misconception. B2C invoices are currently outside the mandatory KSeF scope – that is correct. However, a Romanian retailer that also conducts any B2B sales in Poland must issue those B2B invoices through KSeF from the applicable deadline. Mixed B2B/B2C businesses cannot treat the B2C exemption as covering their entire Polish invoicing activity. Additionally, the Ministry of Finance has indicated that B2C invoicing may be brought within KSeF scope in a later phase of the programme, so retailers should monitor legislative developments through 2026 and 2027.

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 – including Romanian and broader CEE-based groups – and in-house legal teams managing Polish tax obligations from abroad. 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.