KSeF – Everything You Need to Know About the National e-Invoicing System

The National e-Invoicing System (KSeF) is one of the most significant changes in Poland’s tax system in recent years. While its goal is to simplify and tighten settlements, for many companies it means adjusting internal accounting procedures and document workflows. The introduction of structured invoices also brings new obligations, deadlines, and challenges for accounting offices and finance departments. It’s worth understanding today how it works and what benefits it offers.

KSeF is an IT system created by the Ministry of Finance to standardize invoice circulation, increase data security, and accelerate settlements between companies—all thanks to structured invoices and broad digitization of accounting processes. E-invoices issued under KSeF will coexist with traditional paper invoices and current electronic invoices, but within the next few months they will become the standard solution used in everyday business transactions by most companies. This change means not only a new way of documenting transactions but also full data integration with tax administration, enabling faster verification of settlements and reducing tax fraud. For entrepreneurs, KSeF is both a challenge and an opportunity: it requires implementing new tools and adapting processes, but it also opens the door to automation and greater transparency.

Key Implementation Dates

The obligation to use KSeF is divided into two stages to help smaller companies prepare:

• From February 1, 2026 – mandatory for companies whose 2024 sales exceeded PLN 200 million gross.
• From April 1, 2026 – mandatory for all other businesses.

A transitional period runs until December 31, 2026, during which invoices can still be issued outside KSeF (paper or electronic) if monthly sales with VAT do not exceed PLN 10,000. Voluntary use of KSeF has been possible since January 2022.

How Does KSeF Work in Practice?

The invoicing process under KSeF differs significantly from the traditional model:

• Invoice creation – in an accounting system integrated with KSeF.
• Sending to KSeF – the system automatically transmits the invoice in XML format to the central platform.
• Verification – KSeF checks structure and data accuracy, registers the invoice, assigns an ID, and issues an Official Receipt Confirmation (UPO).
• Access for buyer – once approved, the invoice is available in KSeF for the buyer.
• Download by buyer – the buyer can access and download invoices anytime.

What Is a Structured e-Invoice?

A structured e-invoice is an electronic accounting document issued and transmitted via KSeF in a standardized XML format. Its uniform structure makes data readable for both humans and financial systems, enabling automatic processing. Mandatory fields include seller’s tax ID, issue date, and invoice number—missing any of these results in rejection.

Is Buyer Consent Required?

Until March 31, 2026, issuing a structured invoice requires buyer consent. From April 1, 2026 (or February 1 for large firms), consent is no longer needed—KSeF becomes mandatory for all covered entities.

Why Paper or PDF Invoices Don’t Meet KSeF Requirements

Traditional invoices lack the standardized XML structure required for automated processing. They are also vulnerable to damage, loss, or unauthorized changes. KSeF eliminates these risks by ensuring integrity, security, and durability through a central repository.

Benefits of Implementing KSeF

• Standardization – one invoice template reduces errors and supports automation.
• Faster circulation – invoices reach recipients almost instantly.
• Data automation – eliminates manual data entry.
• Central access – invoices stored for 10 years.
• Faster VAT refunds – 40 days instead of 60 for KSeF users.
• Transparency and security – guarantees invoice authenticity.

nAxiom: Flexible Low-Code Solution

The nAxiom platform is a modern tool supporting companies in preparing for the mandatory implementation of the KSeF (Key Accounting Standards) system. Thanks to process automation, ERP system integration, and high flexibility, companies can effectively streamline their invoice management, billing, and internal control mechanisms. The system provides communication with the KSeF, allowing for automatic sending and receiving of invoices without user intervention, streamlining the entire accounting process. The platform combines advanced data security with intuitive operation, allowing for quick team onboarding and simplifying daily document management. Furthermore, nAxiom records every stage of invoice processing, enables the generation of detailed reports, and sends notifications of status changes, supporting oversight, control, and compliance with audit procedures.

KSeF – From Obligation to Competitive Advantage

Using the KSeF system not only fulfills a regulatory obligation but also provides a real opportunity to streamline financial processes. The modern system paves the way for the automation and digitization of document workflows, allowing for greater control over payments, increased security, and faster operations. Solutions such as the nAxiom platform play a key role in the process of adapting new regulations and the ongoing digitization of accounting processes. This enables the full integration of internal ERP systems with KSeF. This makes implementing electronic invoice workflow simpler and more effective – reducing manual errors, increasing process transparency, and automating the control and approval of cost documents. A feature of the nAxiom platform, developed using low-code technology, is the ability to embed the platform's integration logic with another system as a new step in existing processes, allowing for the adaptation of existing business processes instead of having to create a new, dedicated process.