A Spanish company with a Polish subsidiary receives an email from its Warsaw-based accountant in early 2026: "KSeF goes live in April – you need to act now." The finance director in Madrid has never heard of KSeF. The subsidiary's invoicing software is not connected to any government platform. The clock is already running.

KSeF – the Krajowy System e-Faktur (National e-Invoice System) – is Poland's mandatory structured invoicing platform, administered by the National Revenue Administration (KAS). From 1 February 2026, large taxpayers with annual VAT turnover above PLN 200 million are required to issue all B2B invoices exclusively through KSeF. The obligation extends to all remaining VAT-registered businesses from 1 April 2026. Spanish parent companies with Polish subsidiaries fall within scope from that date. Non-compliance triggers financial penalties and disrupts VAT settlement cycles.

This alert explains what changed, which Spanish-owned entities are affected, and what your finance and legal teams must do before the April deadline. Three action items stand out: system integration, staff training, and a compliance review of existing invoice workflows.

What has changed under Polish tax law – and when?

Polish tax legislation introduced KSeF as a phased mandatory requirement. The National Court Register (KRS) and the National Revenue Administration (KAS) are the two primary state bodies your Polish subsidiary will interact with during onboarding. The Polish Financial Supervision Authority (KNF) is not directly involved in KSeF, but regulated entities under its oversight must still comply with the invoicing rules.

The phased rollout works as follows. Large taxpayers – those whose annual VAT turnover exceeded PLN 200 million in 2024 – became obligated from 1 February 2026. All other VAT-registered businesses in Poland, including subsidiaries of Spanish groups, face the hard deadline of 1 April 2026. After that date, issuing a VAT invoice outside KSeF is treated as a failure to issue an invoice at all. That classification carries penalties of up to 100% of the VAT shown on the non-compliant document.

The system works through structured XML files in the FA(2) schema. Every invoice receives a unique KSeF number assigned by the Ministry of Finance platform within seconds of upload. That number becomes the legal reference for the document. Buyers can verify invoices in real time. The 60-day deemed-receipt rule means that if a buyer does not confirm receipt through KSeF, the invoice is still treated as received 60 days after issue – which affects payment terms and VAT deduction timing.

  • Mandatory from 1 February 2026 for large taxpayers (PLN 200m+ turnover)
  • Mandatory from 1 April 2026 for all remaining VAT-registered entities
  • Penalty: up to 100% of VAT on each non-compliant invoice
  • 60-day deemed-receipt rule affects buyer-side VAT deduction
  • Invoices issued outside KSeF after the deadline have no legal standing

Spanish groups that consolidated their Polish operations under a single VAT number should check whether that entity crossed the PLN 200 million threshold. If it did, the February deadline already applies. Missing it forfeits the right to issue valid invoices and precludes VAT recovery on related purchases – an irreversible consequence for ongoing supply chains.

Who is affected among Spanish-owned entities in Poland?

The obligation attaches to the Polish entity, not the Spanish parent. However, the practical burden falls on group finance teams, ERP administrators, and tax advisors in both countries. Any Spanish company that holds a Polish subsidiary registered for VAT – whether a spółka z ograniczoną odpowiedzialnością (private limited liability company, sp. z o.o.) or a branch – is within scope from 1 April 2026 at the latest.

We assisted a manufacturing client operating from the Mazowieckie region in completing its KSeF integration and staff authorisation process ahead of the April 2026 deadline (winter 2026). The entity had 14 active ERP modules issuing invoices across three product lines. Consolidating those into a single KSeF-compliant output required six weeks of technical work and one formal amendment to the company's VAT registration data held by KAS.

Foreign investors sometimes assume that their Polish subsidiary can continue using PDF invoices sent by email. That assumption is incorrect after 1 April 2026. The only exception covers invoices issued to private individuals (B2C) and certain cross-border transactions where the foreign buyer is not registered for VAT in Poland. B2B transactions between two Polish VAT numbers – or between a Polish entity and a foreign entity registered for Polish VAT – must go through KSeF without exception. This directly affects Spanish companies that are themselves registered for Polish VAT due to distance selling or local warehousing arrangements.

Transfer pricing documentation and IP Box calculations are not directly altered by KSeF. However, the invoice data flowing through KSeF will be visible to KAS in real time. That visibility increases the risk of audit triggers for intercompany transactions. A tax advisor Warsaw-based teams should review intercompany pricing before the system goes live. Polish tax law already requires contemporaneous transfer pricing documentation; KSeF adds a new layer of transactional transparency.

We also helped a technology services group based in Małopolska restructure its intercompany invoicing model in preparation for KSeF (spring 2026). The group had relied on a family foundation structure for IP holding purposes. After KSeF onboarding, the invoice flows between the foundation and its operating subsidiary required reclassification to ensure the correct VAT treatment was applied at the point of KSeF upload.

What must your business do before 1 April 2026?

Three steps are non-negotiable. First, your Polish subsidiary must obtain a KSeF authorisation token from KAS. This token allows the ERP system or accounting software to connect to the government API. The application is submitted electronically and typically processed within 3 business days. Second, the entity's invoice template must be converted to the FA(2) XML schema. Third, at least one employee must be designated as the KSeF system administrator with full authorisation rights.

The broader compliance review should also address the following items before the deadline:

  • Verify that all VAT registration data in KAS matches the current KRS entry
  • Confirm that your ERP vendor has released a KSeF-certified integration module
  • Review contracts with Polish customers that reference "invoice date" – KSeF issue date now governs
  • Check whether any Polish VAT registration held by the Spanish parent triggers a separate KSeF obligation

Spanish groups with Polish operations under a double tax treaty arrangement – including those relying on the Poland-Spain tax treaty, which shares structural features with the double tax treaty framework analysed in our US treaty guide – should also assess whether the KSeF data stream affects their permanent establishment position. KAS can now cross-reference invoice volumes against declared PE thresholds automatically.

For subsidiaries already subject to a compliance programme, KSeF integration should be treated as a mandatory update to existing internal controls. Our compliance programme design guide for Spain subsidiaries in Poland sets out the governance framework that supports this update. Groups operating across multiple EU jurisdictions should also note that the KSeF timeline differs from Spain's own SII (Suministro Inmediato de Información) system – the two platforms do not interconnect, and invoice data must be reported separately to each authority. For a comparison with the Swiss rollout schedule, see our KSeF deadline timeline for companies in Switzerland.

The window to act is narrow. Businesses that delay integration past mid-March 2026 risk running out of time to test the API connection before the live date. A failed test environment is not an excuse recognised by KAS for late compliance.

Specific circumstances of your Polish subsidiary require individual assessment. Missing the 1 April 2026 deadline precludes valid invoice issuance and triggers penalties that cannot be reversed retroactively.

If your Spanish group holds a Polish VAT-registered entity – regardless of size or sector – contact our team now for a KSeF readiness review: info@kordeckipartners.com.

Frequently asked questions

Q: Does KSeF apply to a Spanish company that is only registered for Polish VAT but has no Polish legal entity?

A: Yes, in certain circumstances. A foreign entity registered for VAT in Poland – for example, due to local warehousing or distance selling above the PLN 42,000 threshold – may be required to use KSeF for its Polish VAT invoices. The obligation depends on the nature of the transactions and whether the counterparty is a Polish VAT payer. A tax advisor should assess the specific registration profile before the April deadline.

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

A: Technical onboarding – from API token application to a tested live connection – typically takes between three and eight weeks, depending on the ERP system in use. ERP vendors charge separately for certified integration modules; costs vary widely. Legal and tax advisory fees for a compliance review and authorisation setup typically range from PLN 5,000 to PLN 20,000 for a mid-size subsidiary. Starting in January 2026 is the minimum safe timeline for an April go-live.

Q: Can a Spanish parent company manage KSeF authorisations on behalf of its Polish subsidiary?

A: No. KSeF authorisations are granted by KAS to individuals or entities identified by their Polish tax identification number (NIP). The Spanish parent cannot hold a KSeF token directly. The Polish subsidiary must designate authorised persons – typically its management board members or a designated tax representative – who each receive individual access credentials. This is a common misconception among foreign groups that centralise finance functions abroad.

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 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.