KSeF in Poland: What is the E-Invoicing Mandate and How Can You Prepare?

Poland's mandatory KSeF e-invoicing mandate starts in 2026. Here’s your roadmap for technical integration, compliance and efficiency gains.

Poland is transforming its invoicing landscape with the introduction of the Krajowy System e-Faktur (KSeF), a mandatory national system for VAT-registered entities in Poland. This guide is your roadmap for practical implementation, including technical requirements and how to prepare your business for a seamless transition to KSeF and the e-invoicing mandate. With SEEBURGER’s extensive experience in global e-invoicing, what begins as a mandate can become a measurable competitive advantage for your business. The SEEBURGER BIS Platform is your cloud-native integration platform for connecting systems and ensuring compliance with KSeF and other country-specific mandates.

Poland plans to introduce B2B e-invoicing in 2026. KSeF is the acronym for Krajowy System e-Faktur – Poland's official national platform for structured electronic invoicing. For companies operating in Poland, KSeF isn't just a regulatory update; it's a fundamental shift in how invoices are issued, received, and processed.

The core function of the KSeF system is to centralize the exchange of invoices. Instead of businesses sending invoices directly to each other, all invoices must first be submitted to the KSeF platform for verification, assignment of a unique identification number (KSeF-ID) and official recording. Starting in 2026, all VAT-registered companies in Poland will be required to exchange invoices exclusively through the centralized KSeF system. This move is designed to curb tax fraud, reduce manual errors, and standardize invoicing nationwide. Understanding the technical requirements, revised timelines, and practical implications is crucial for ensuring compliance and leveraging this change as an opportunity for greater efficiency and process automation.

KSeF positions Poland among a growing list of countries implementing Continuous Transaction Controls (CTCs) to enhance tax transparency and modernize business processes. This CTC model gives Polish tax authorities real-time insight into transactions to support the EU’s ViDA/VAT in the digital age initiative and combat fraud. For businesses, it introduces a standardized process that reduces the potential for errors while opening new avenues for automation in finance and accounting departments.

The mandate applies to:

Businesses in Poland
supplying goods or services (B2B)

Foreign taxpayers
with a permanent establishment in Poland

Public institutions
receiving invoices (B2G)

Private consumer (B2C) transactions are not included in the mandate’s scope.

The rollout of the mandatory KSeF system has undergone several revisions to ensure a stable and well-tested architecture. Following a technical audit and public consultations, the Polish Ministry of Finance has confirmed a new, phased implementation schedule for 2026 and beyond.

The mandatory deadlines have been set as follows:

February 1, 2026	Go-live data for the final production environment. Mandatory for large taxpayers, defined as businesses with an annual turnover exceeding PLN 200 million in 2025.
April 1, 2026	Mandatory for all other taxpayers, including small and medium-sized enterprises.
January 1, 2027	Mandatory for micro-enterprises and entities issuing invoices under PLN 450 with a monthly turnover below PLN 10,000.

This revised timeline provides businesses with more preparation time. Key milestones leading up to the mandate include the public test phase for the new API, which began at the end of September 2025, and the availability of pre-production and certificate modules in November 2025.

Successful implementation of KSeF requires careful attention to several technical building blocks. Whether your organization is a small local business or part of a large European company with a Polish subsidiary, understanding these technical requirements is essential for a smooth e-invoicing process.

Data models and validation

Invoices submitted to KSeF must adhere to a specific XML data structure. The current KSeF schema is FA(3), which replaces the previous FA(2) version. This schema contains over 300 fields, some of which are mandatory while others are conditional based on the transaction. Your ERP system must be able to generate invoices that correctly map to the FA(3) format to avoid rejections.

Authorization and authentication

Access to the KSeF system is restricted to authorized individuals. Initially, access is managed via qualified certificates and KSeF tokens. From January 1, 2027, tokens will be replaced by a new KSeF certificate, which will also support offline scenarios. Clear roles and delegations must be established to ensure every access is traceable and invoice authenticity is guaranteed.

API process and confirmation

Your system will communicate with KSeF through an API. After submitting an e-faktura KSeF, the system confirms receipt with an official message known as a UPO (Urzędowe Poświadczenie Odbioru, an official acknowledgment of receipt) and assigns a unique KSeF-ID. This process must be highly stable, requiring robust integration with comprehensive logging and error-handling mechanisms.

QR code

A uniform QR code is a mandatory component for all electronic invoices under the KSeF mandate. The KSeF-ID is converted into a QR code, which must be included on any human-readable copy of the invoice (like a PDF). This ensures the invoice remains traceable even outside the KSeF platform. QR codes must also be generated in offline mode.

End-to-end synchronization

Outgoing invoices:
The process must be seamless, from extracting ERP data and converting it to the FA(3) format, to transmitting it to KSeF, receiving the UPO and KSeF-ID and generating a QR code. The invoice is stored centrally electronically – a physical or duplicate copy is no longer required by law. The archiving obligation still exists but indicates a successful transmission (e.g. UPO, KSeF ID). The invoice is stored in the KSeF system, which is considered the official archive. Sending the invoice to the customer is not mandatory if the customer has access to KSeF.

Incoming invoices:
Your system must regularly query KSeF for new faktury KSeF (i.e. invoices that are issued and stored in the KSeF platform), retrieve the invoice lists, validate them, enrich the data, and post them to your ERP system automatically.

No system is infallible, and KSeF is no exception. The Polish government has planned for system unavailability, whether due to maintenance, cyber attacks or server outages. Businesses need to establish clear organizational processes to manage offline scenarios and maintain business continuity.

It is important to distinguish between Offline24 and system failure.

Offline24 is a regular fallback mode that allows invoices to be issued when internet access is unavailable or when technical issues prevent immediate submission to KSeF.

In contrast, system failure refers to official unavailability of the KSeF platform as declared by the Ministry of Finance.

In such cases, companies have up to 7 working days to submit the invoice to KSeF after the system is restored.

During a KSeF outage, companies are permitted to:

Issue invoices offline outside the central system.
Add a QR code to these offline invoices.
Record them in KSeF no later than the next business day after the system is restored.

To prepare, companies must have issuer certificates in place to generate QR codes during an outage. It's crucial to define clear internal procedures for switching to offline mode, capturing invoices and linking the later-assigned KSeF-ID back to ERP records.

For domestic B2B transactions in which the customer has a Polish VAT number, the invoice must be successfully submitted to KSeF and a KSeF-ID must be assigned before the invoice is delivered to the customer. This rule applies even in offline scenarios and is essential for compliance with Polish VAT law.

While e-invoicing compliance through integration is the primary driver, the KSeF mandate presents a significant opportunity to automate and streamline accounting processes, particularly for incoming invoices. The goal is touchless booking – the fully automated posting of invoices without any human intervention. Achieving this requires a solid foundation built on data quality and clear processes.

Key enablers include:

Clean supplier master data

Accurate supplier names, details, and bank information are essential for the system to correctly route invoices.

Pre-defined account assignments

Including cost centers or project codes in purchase orders enables automatic carryover, reducing the burden on accounting teams.

Accurate tax logic

Up-to-date VAT rates and correct tax codes prevent automated postings from failing.

Clear references

Including purchase order numbers or contract IDs on invoices allows for automatic matching.

By focusing on these areas, businesses can turn the challenge of KSeF into an advantage and realize significant efficiency gains.

Integrating KSeF into your existing system landscape is a complex challenge, especially when your ERP system produces data in a different format than the FA(3) KSeF structure. This is where a strategic partner like SEEBURGER makes a difference.

The SEEBURGER BIS Platform is an AI-assisted platform for secure, scalable integration that simplifies complexity and accelerates automation. Our experience in global e-invoicing and Peppol integration services makes us the ideal partner for your KSeF journey.

SEEBURGER BIS offers a centralized, cloud-native integration platform for managing inbound and outbound invoices.

Here’s how BIS can ensure that you comply with all KSeF requirements:

Our solution integrates flawlessly with any ERP landscape, including SAP S/4HANA, bridging the gap between your internal processes and the KSeF technical requirements. We handle the complex mapping from your ERP format to the FA(3) structure, absorbing future changes without disrupting your systems.

We manage the entire API communication process, including session management, transmitting invoices, collecting the UPO confirmation and generating the mandatory QR code. Our solution features robust logging, retries and error-handling to ensure stability even during KSeF outages.

SEEBURGER enables end-to-end synchronization for both incoming and outgoing invoices. We help you establish automated workflows and achieve touchless booking, turning regulatory compliance into operational excellence.

From KSeF consulting to implementation and beyond, our experts provide guidance and best practices to reduce your time-to-value and ensure success. We stay ahead of regulatory changes, so you don't have to.

The KSeF mandate is coming soon in 2026. With SEEBURGER Consulting Services as your trusted partner, you can prepare in advance and approach the deadline with confidence that your operations will be more efficient and compliant than ever before.