A Czech company supplying goods or services to a Polish buyer receives an unexpected message from its Warsaw counterpart: invoices must now be issued through a new government platform. No platform access, no payment. This is not a contractual quirk – it is the direct commercial consequence of Poland's mandatory e-invoicing system, the National e-Invoice System (Krajowy System e-Faktur, KSeF), which reshapes how cross-border transactions with Polish entities are documented and settled.
KSeF is Poland's centralised electronic invoicing platform, administered by the National Revenue Administration (Krajowa Administracja Skarbowa, KAS). From 1 February 2026, all Polish VAT-registered taxpayers must issue structured invoices exclusively through KSeF. Czech businesses that invoice Polish counterparts face an immediate compliance decision: adapt their invoicing infrastructure or risk delayed payments, broken supply chains, and potential loss of Polish contracts worth months of revenue.
This alert covers three things. First, what KSeF actually requires and when the obligation bites. Second, which Czech businesses are affected and how seriously. Third, the concrete steps your finance and legal teams should take before the February 2026 deadline.
What has changed under Polish tax law – and when?
KSeF was introduced under Polish tax legislation as a structured XML invoice format transmitted through a government portal operated by the Ministry of Finance (Ministerstwo Finansów). The system assigns each invoice a unique KSeF number, which becomes the legal proof of the transaction for Polish VAT purposes. Without that number, the invoice does not exist in the eyes of Polish tax law.
The mandatory rollout follows a phased schedule. Polish taxpayers whose annual turnover exceeded PLN 200 million in 2024 must comply from 1 February 2026. All remaining Polish VAT payers follow on 1 April 2026. These are hard statutory deadlines – there is no grace period for technical difficulties after the go-live date. The National Court Register (Krajowy Rejestr Sądowy, KRS) records of Polish counterparties will not shield a Czech supplier from the commercial fallout of non-compliant invoicing.
Foreign entities – including Czech companies – are not directly obligated to register in KSeF. The obligation sits with the Polish buyer or the Polish VAT-registered entity in the transaction. However, if a Czech company is VAT-registered in Poland (for example, through a fixed establishment or a Polish branch), it falls squarely within the mandatory scope from the applicable deadline. That distinction matters enormously for structuring decisions. For a detailed breakdown of how penalties are calculated and avoided, see our guide on KSeF penalties calculation and avoidance strategies.
One figure deserves emphasis. Invoices issued outside KSeF after the mandatory date are treated as not issued at all. The Polish buyer loses the right to deduct input VAT on those purchases. That creates immediate financial pressure on your Polish client – and immediate commercial pressure on you.
Which Czech businesses are most exposed?
Exposure depends on two variables: whether the Czech entity holds Polish VAT registration, and how deeply embedded it is in Polish supply chains. Both factors are often underestimated.
Czech manufacturers exporting to Poland under DDP (Delivered Duty Paid) Incoterms frequently trigger Polish VAT registration obligations without realising it. Once registered, they are subject to KSeF from the applicable deadline. The Polish Financial Supervision Authority (Komisja Nadzoru Finansowego, KNF) does not regulate invoicing directly, but financial sector clients in Poland are among the most demanding in requiring KSeF-compliant documentation from their suppliers.
Three categories of Czech business face the sharpest exposure:
- Czech companies with existing Polish VAT registration numbers
- Czech subsidiaries of multinational groups that invoice Polish group entities
- Czech IT and service providers billing Polish clients under framework agreements
For Czech investors evaluating their Polish entity structure, the choice between a branch and a subsidiary carries direct KSeF implications. A branch creates a fixed establishment and likely triggers Polish VAT registration. A subsidiary incorporated as a Polish spółka z ograniczoną odpowiedzialnością (limited liability company, sp. z o.o.) is a Polish taxpayer from day one. Our comparison of sp. z o.o. vs SA – decision matrix for Czech Republic investors addresses these structural trade-offs in detail.
We secured a reclassification of a Czech IT supplier's Polish VAT position for a technology client in the Małopolska region (autumn 2025), removing an inadvertent KSeF obligation that had gone unnoticed for two years. The saving in remediation costs exceeded PLN 400,000.
What should your business do before the deadline?
Time is short. With the first mandatory date at 1 February 2026, Czech businesses with Polish VAT exposure have a narrow window to audit, adapt, and test. Leaving this to January is not a strategy – it is a risk that forfeits contractual relationships built over years.
The immediate action list breaks into four areas:
- VAT registration audit: confirm whether your Czech entity holds or should hold Polish VAT registration
- ERP and billing system update: structured KSeF XML (FA(2) schema) must be generated and transmitted via API or manual upload
- Counterparty mapping: identify all Polish clients and confirm their KSeF go-live dates
- Transfer pricing documentation: if intra-group invoices are affected, update your transfer pricing file to reflect the new invoicing format
IP Box regimes and family foundation structures used by Polish counterparties do not affect KSeF obligations directly. However, a tax advisor Warsaw-based practices frequently see is the assumption that holding income through a family foundation exempts the underlying operating company from KSeF. It does not. The operating entity's invoicing obligations remain unchanged.
Our team assisted a Czech-owned distribution business in Silesia (winter 2025) in completing a full KSeF readiness review within six weeks. The project covered ERP configuration, API integration testing, and staff training – all before the client's largest Polish customer imposed its own internal KSeF compliance deadline. For a parallel perspective on how the same system affects operations in a neighbouring market, our alert on what KSeF means for your business in Slovakia provides useful context.
Polish tax law provides no safe harbour for foreign businesses that miss the deadline because of technical unpreparedness. The irreversible consequence is simple: your Polish buyer cannot deduct VAT, and the commercial relationship deteriorates from there.
What to prepare – KSeF readiness checklist:
- Confirm Polish VAT registration status of all Czech group entities
- Map all invoices currently issued to Polish VAT-registered counterparties
- Engage ERP vendor to implement FA(2) XML schema and KSeF API connection
- Test invoice transmission in the KSeF sandbox environment before 1 January 2026
- Brief finance and accounts-receivable teams on the new workflow
Specific situations require specific assessments. If your Czech business invoices Polish clients and you are uncertain whether KSeF applies to your entity, the window for structured preparation is closing. To receive an expert assessment of your KSeF exposure and a tailored compliance roadmap, contact info@kordeckipartners.com.
Frequently asked questions
Q: Does a Czech company without Polish VAT registration need to use KSeF?
A: No – KSeF is a Polish statutory obligation that applies to Polish VAT-registered taxpayers. A Czech entity that sells to Polish buyers but holds no Polish VAT registration number is not directly required to issue invoices through KSeF. However, if that entity is registered for Polish VAT – even voluntarily – the obligation applies from the mandatory deadline relevant to its turnover threshold.
Q: How long does it take to integrate an ERP system with KSeF?
A: Integration timelines vary. Simple accounting software with an existing KSeF plugin can be configured in two to four weeks. Custom ERP environments or legacy billing systems typically require eight to twelve weeks of development, testing, and user acceptance. Starting in December 2025 for a February 2026 deadline leaves almost no margin for error.
Q: Is KSeF the same as the Czech electronic invoicing system?
A: No. KSeF is a Polish system with no direct equivalent in Czech Republic as of early 2026. The Czech Republic has its own VAT reporting obligations, but mandatory structured e-invoicing through a centralised government portal is a Polish-specific requirement. Czech businesses should not assume that compliance with Czech invoicing rules satisfies Polish KSeF obligations for their Polish-registered entities or transactions.
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.