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KSeF – What It Is and What the National e-Invoicing System Is Used For?

ByMateusz

The National e-Invoicing System is a revolution in invoicing that moves Polish business into the digital era. The circulation of documents is meant to be faster and easier, but the change is also intended to tighten the tax system. KSeF (this is the common abbreviation for the system) will change the process of issuing, receiving and storing invoices. It applies to all entrepreneurs, regardless of whether they run a sole proprietorship or a company. What is KSeF, how does it work, and when will your business have to use it? Get ready for the change with Solpoint!

Key take aways: TL;DR:

  • What is KSeF?
  • (National e-Invoice System) is a nationwide, centralised system for issuing, receiving, sending and archiving structured (XML) invoices. It replaces paper and PDF invoices with a single, standard format supported by the tax authorities. It is a government server – a central state platform through which sales invoices between businesses are processed.
  • Why was it introduced?
  • To digitise invoicing, streamline document circulation, increase tax control and reduce VAT fraud.
  • How does it work?
  • The invoice is sent to the KSeF government server → it receives a unique number → it is automatically stored in the system (for 10 years) → the recipient downloads it from KSeF.
  • When will it become mandatory?
    • from 1 February 2026 – large companies. Therefore, from that date, you must have an account to receive invoices, e.g. from petrol stations or Ikea;
    • from 1 April 2026 – other businesses, as issuers
    • from 1 January 2027 – the smallest
    • (receiving invoices via KSeF will be mandatory for everyone from February 2026)
  • Access to the system:
  • Via tokens and, ultimately, KSeF certificates, with the possibility of granting authorisations, e.g. to accounting offices.
  • Benefits:
  • no paper archiving, easier audits, potentially faster VAT refunds.
  • Challenges:
  • the need to integrate systems, change accounting processes and prepare companies technically.

Table of Contents

What is KSeF?
How does the National e-Invoicing System work?
What does the KSeF number mean?
What is a token in KSeF?
KSeF certificate – what is it and what is it used for?
KSeF from when – key dates and obligations
Failures, i.e. extraordinary modes in KSeF
Penalties in KSeF
KSeF – advantages and difficulties
How to prepare for KSeF – step by step
Summary
FAQ – the most frequently asked questions about what KSeF is

From this article you will learn:

what KSeF is and what it is supposed to be used for
KSeF – what it means for your business
how the National e-Invoicing System works
what the number and token in KSeF are
what a KSeF certificate is
from when KSeF will be mandatory

What is KSeF?

According to the Polish VAT Act, the National e-Invoicing System (KSeF) is a tool for issuing, receiving and sending structured invoices, i.e. e-invoices. It will cover all entrepreneurs in Poland – both sole proprietorships and companies. After an invoice is sent to the National e-Invoicing System, it receives a unique identification number in KSeF. From that moment, an ordinary electronic document is considered a so-called structured invoice – however, it must meet certain requirements. The government’s basic tool for handling KSeF is the Taxpayer Application.

Thanks to KSeF, the generated e-invoice is sent immediately not only to the contractor (there will no longer be a need to exchange invoices with each other), but also to the tax authority. The Ministry of Finance introduced this solution to speed up the circulation of documents, tighten the system and minimize the number of tax crimes. When mandatory KSeF enters into force, the tax authorities will know not only in which shop we made a purchase and for what amount, but also exactly what we bought – i.e. what items are listed on the invoice.

Apart from tightening the system, KSeF is intended, among other things, to:
facilitate the exchange of invoices between entrepreneurs (an e-document cannot be lost or deleted)
standardize invoicing processes
speed up VAT refunds (from 60 to 40 days)
facilitate the archiving of invoices (they will be stored in KSeF for 10 years)

Logging in to KSeF

Already today you can log in to KSeF, as well as to the test environment of the KSeF 2.0 Taxpayer Application. You do not need to register – all entrepreneurs have access to KSeF, and a sole proprietor can log in simply using a Trusted Profile (Profil Zaufany). In the case of companies, it will first be necessary to submit a ZAW-FA notification in order to grant one of the shareholders the role of “administrator” of the company’s account in KSeF, who will log in for the first time and then will be able to grant permissions to other people in the company.

Structured invoice – what is it and what are its features?

The structured invoice mentioned above, i.e. an e-invoice, is a document issued in accordance with the applicable schema (schema) provided by the Ministry of Finance. The schema ensures uniformity of all documents and their easy reading by accounting software.

A structured invoice differs from classic documents in several elements:
it is saved in XML format
it has all fields required by the Ministry of Finance
it is marked with a KSeF number

Which invoices will be in KSeF and which will be outside?

Although KSeF applies to all entrepreneurs in Poland, it does not cover all accounting documents – some will be excluded from the digital circulation.

Outside the National e-Invoicing System will remain simplified invoices, invoices under special procedures (OSS, IOSS) or transport documents. Adding invoices to KSeF will be voluntary in the case of invoices for private individuals (consumers) and RR invoices.

Private individuals do not have access to KSeF, so they will not be able to receive an invoice from the National e-Invoicing System. Therefore, entrepreneurs will have to provide consumers with a visualization of the invoice, e.g. in the form of a PDF downloaded from an application made available by Solpoint or the Taxpayer Application. However, sending such an invoice to KSeF will be voluntary. It is still worth considering adding such documents to KSeF as well, in order to standardize accounting.

In the case of foreign contractors, the situation is different – an invoice for a foreign contractor must be sent to KSeF obligatorily. However, foreign companies do not have access to the National e-Invoicing System, so it will be necessary to send them a visualization of the document, e.g. in the form of a PDF.

KSeF – what does it mean for your company?

The National e-Invoicing System is a revolution for Polish companies. The solution eliminates traditional paper invoices and PDFs, moving the entire settlement process into the digital space – one, central invoice system. Already from 1 February 2026, every entrepreneur will be obliged to receive invoices through KSeF. Mandatory sending of invoices to KSeF.

How to use KSeF? For example, through the government website – the Taxpayer Application. However, it is quite a basic tool with limited capabilities. Especially with a larger number of documents and more complicated accounting, using it may prove very difficult. Each time, you will also have to log in to the government solution using a Trusted Profile, while to the Saldeo application you can log in conveniently, e.g. using biometrics. Basic tools (the KSeF Taxpayer Application or e-mikrofirma for sole proprietors) do not inform about new documents, and issuing an invoice itself is time-consuming. Therefore, it is worth using integrated accounting software.

How does the National e-Invoicing System work?

The National e-Invoicing System is a platform for issuing and receiving invoices electronically. KSeF is also described as a central repository storing information from invoices – the system is like a big box for documents. You can “put” invoices there (by sending an appropriate XML file) and also “take them out” freely – i.e. make them available to your contractors and tax authorities. Invoices in KSeF will be archived for at least 10 years, which removes this obligation from the entrepreneur.

What does the KSeF number mean?

KSeF is a system based on IT solutions. That is why the KSeF number is so important in the National e-Invoicing System. Below we explain what this unique number is and what its significance is in KSeF.

KSeF number – what is it?

The KSeF number is a unique number, an identifier, assigned to each invoice in the National e-Invoicing System. It is considered that an invoice has been delivered to KSeF and, at the same time, by default received by the contractor, at the moment the KSeF number is assigned to it by the system. The number consists of a total of 5 parts separated by hyphens:
the seller’s NIP (tax ID)
the date the invoice is sent (YYYYMMDD)
the first technical part (6 characters)
the second technical part (6 characters)
the checksum (2 characters)

What is a token in KSeF?

An authorization token is the current method of logging in to the National e-Invoicing System. This unique number consisting of 40 characters is assigned to a specific entity. When logging in to the system, you can generate different types of tokens with different scopes of permissions (viewing invoices, issuing them, or both). Ultimately, tokens will be replaced by more secure KSeF certificates, which can already be generated from 1 November 2025.

KSeF tokens are valid only until the end of 2026. During this time they will function in parallel with KSeF certificates, which we describe later in the text. From 1 January 2027, of the two solutions only KSeF certificates will remain.

What is a token used for? A token is used for API, i.e. the programming interface of a selected application, to establish a connection with KSeF. In very simple terms, this means that thanks to the token and the API you can integrate your accounting or invoicing software with the KSeF database. In this way you will issue invoices, receive documents, etc. Soon tokens will be replaced by KSeF certificates.

At Solpoint, the API works automatically in the background of the application and you do not have to worry about the correct transmission of information.

The KSeF authorization token should be treated as a confidential password to the system. Importantly, when using it, no additional user action is required to send an invoice or download it in KSeF. A person who has a generated token can perform various operations on behalf of the taxpayer.

A KSeF token can be generated on the ministry’s website by logging in to the National e-Invoicing System. It is not mandatory – the taxpayer decides whether they want to use it. As a rule, tokens do not have an expiry date unless they are revoked by the user.

In 2027, tokens will be completely replaced by KSeF certificates.

KSeF certificate – what is it and what is it used for?

A KSeF certificate is another method of confirming identity in the e-invoicing system, which ultimately will be the basic and main form of authentication for sole proprietorships. It is a special cryptographic file that works in the background of an application and confirms the identity of your business. It can be compared to a kind of company seal in the digital world. A KSeF certificate is also necessary, among other things, when issuing invoices in special modes: offline24, offline (system unavailability) and emergency mode. We will describe them later in the article.

From 1 January 2027, certificates will become the only method of authentication in KSeF, thus eliminating the use of tokens.

How to obtain a KSeF certificate? It can be generated from 1 November 2025 directly on the KSeF portal – in the Certificates and Permissions Module (MCU). The granted KSeF certificate will be valid for 2 years.

KSeF from when – key dates and obligations

KSeF, i.e. a real revolution in invoices, is a change that will apply to all entrepreneurs, but it will be introduced in stages. Check from when KSeF will become an inseparable part of your business.

From when will KSeF apply to your company?

KSeF – what is it and from when will the solution become mandatory? According to the act adopted by the Sejm, mandatory issuing of e-invoices within KSeF will start to apply:
from 1 February 2026 – for large companies with turnover above PLN 200 million
from 1 April 2026 – for other entrepreneurs
from 1 January 2027 – for the smallest companies (sales value up to PLN 10,000 per month)

The obligation to receive invoices in KSeF will apply to all entrepreneurs already from 1 February 2026.

Mandatory receiving of invoices in KSeF – from February 2026

Perhaps your company does not have to rush with the National e-Invoicing System, because in terms of issuing invoices it will apply to you only from April 2026 or even January 2027. However, this does not exempt you from receiving invoices via KSeF from February 2026.

A good illustration is the example of fuel stations. Large companies with turnover above PLN 200 million must issue KSeF invoices already from February 2026. This means that these documents will appear in the system immediately and you are obliged to receive them from KSeF – e.g. in the Taxpayer Application or Saldeo. An invoice for electricity, phone or internet? From February 2026 it will also be waiting for the entrepreneur online – in the KSeF system.

It is worth emphasizing the advantages of such a solution. If only the NIP, which is the most important element in the KSeF system, is correctly provided on the invoice – no document will be missed, because it will always be waiting in “our KSeF”. There is no need to send invoices to contractors anymore – they will also find the e-invoices issued to their NIP in “their KSeF”. The accountant? They also have access to your invoices automatically, if you grant them the appropriate permissions in the system.

The end of paper forms, collective PDF bills and other forms of settlements and sending them by email or post is why it is better to prepare in advance for using KSeF.

The SaldeoSmart application will automatically download all your invoices from KSeF and notify you about them!

Date of issuing an e-invoice

The National e-Invoicing System introduces new rules related to the invoice issue date. As a rule, a structured invoice (e-invoice) is considered issued at the moment it is sent to the system, i.e. precisely at the moment the KSeF number is assigned. Not when you issue it locally in your software or save it in draft versions, but only after it is sent to KSeF and receives the KSeF number. The exception will be invoices issued in offline modes. We write about them in the next paragraph.

Therefore, you will not issue invoices retroactively or with delay. The issue date will not be able to be earlier than the date when the document is created and transmitted to KSeF. The exception are extraordinary modes in KSeF.

You can still indicate the sale date – this rule does not change. The invoice must be issued no later than on the 15th day of the month following the month in which the delivery of goods or provision of services took place.

Failures, i.e. extraordinary modes in KSeF

As in any system, KSeF also provides certain exceptions to the rule. Internet outage, technical break in KSeF or other random events? You can issue invoices in one of three emergency modes. These documents will be treated differently than in the case of standard invoicing in KSeF:
Offline mode (KSeF unavailability) – a mode intended to be used in the event of service works in KSeF announced in communications. The invoice issue date in offline mode will be the date indicated by you on the document.
Offline24 mode – this mode allows you to issue an invoice outside KSeF if, for example, you have an internet problem. You edit the document according to the structured invoice template and then you have one business day to send everything to KSeF.
Emergency mode – a mode intended in the event of a KSeF failure. If such an event is announced, you can issue an invoice outside the system, according to the applicable structure, and you have 7 days after the failure is removed to send the document to KSeF. The issue date will be the date indicated by you on the invoice.

In the event of a total failure (e.g. if there is a serious threat to the country or its infrastructure), it is possible to issue paper or electronic invoices without the obligation to send them to KSeF.

Penalties in KSeF

Failure to comply with KSeF obligations may be associated with certain penalties. Their amount varies. The maximum may even reach 100% of the VAT from a given invoice or 18.7% of the value of the entire invoice if it was issued by an entrepreneur who is not an active VAT taxpayer. In practice, the amount of penalties will depend, among other things, on the scale of the offense and demonstrating good faith by the taxpayer.

In the National e-Invoicing System, penalties are imposed in three situations:
failure to issue a structured invoice using KSeF
issuing an invoice that is not compliant with the template when the system is unavailable or has a failure
failure to send to KSeF within the designated time an invoice issued outside the system, e.g. during a failure or in offline mode

The application of penalties for non-compliance with obligations related to KSeF is to be postponed until the end of 2026.

KSeF – advantages and difficulties

The new e-invoicing system is not only the advantages resulting from automation and easier access to invoices. It is also numerous challenges that Polish companies are already facing today.

Advantages of KSeF: automation, faster settlements, data consistency

Among the advantages of KSeF, the new Ministry of Finance platform, it is worth mentioning above all automation, which results from using the tool. You no longer have to send an invoice by post or email – it is enough that you issue it in the KSeF system. Your contractor will receive it without any problem.

Other advantages of the National e-Invoicing System for entrepreneurs:
saving your time
full digitization of the invoicing process
easier tax settlements and fewer formal errors
access to cost invoices immediately after they are issued
faster VAT refund – 40, not 60 days
less bureaucracy

Difficulties of KSeF: new tools, integration, security

Like any novelty, KSeF raises some doubts and at the beginning may cause problems. What may prove to be the main difficulty for companies here? Certainly the transition to a digital model. Digitization currently applies to an increasing number of processes related to running a business. People who do not feel comfortable in such an environment or are used to handling matters offline may have trouble switching to KSeF.

Potential difficulties and obstacles for entrepreneurs:
the need to adapt business processes
possible system failures
complicated regulations regarding KSeF
high penalties for failure to comply with the new regulations
risk of cybercrime

How to prepare for KSeF – step by step

It is worth implementing digitization with KSeF step by step. Check how to prepare your company for the new solutions related to the National e-Invoicing System:
Step 1. Integrate Saldeo with KSeF
By 1 February 2026, integrate Saldeo with KSeF by authorizing it with a token from the Ministry of Finance website.

Detailed instructions in the video below:

Summary

The National e-Invoicing System (KSeF) is an innovative tool introduced in Poland to digitize accounting processes, and also to tighten the tax system and fight VAT fraud more effectively. KSeF enables issuing, receiving and sending structured invoices in electronic form. The system is also intended to speed up and facilitate the circulation of invoices between entrepreneurs.

Invoices sent to KSeF receive a unique identification number, and the authorization token provides secure access to the system. New regulations regarding mandatory use of KSeF will be implemented in stages from 2026 to 2027, depending on the size of the enterprise.

The benefits of implementing KSeF include automation of processes, time savings and a faster VAT refund, but it also poses challenges related to system integration and data security. Accounting software such as Saldeo is already ready for the upcoming changes!

FAQ – the most frequently asked questions about what KSeF is

What does KSeF mean?

KSeF, i.e. the National e-Invoicing System, is a digital platform that enables generating, sending and receiving structured electronic invoices. The solution was introduced to tighten the tax system and reduce VAT fraud, as well as to speed up tax refunds.

What is the KSeF number and the authorization token?

The KSeF number is a unique identifier of each invoice in the system. It consists of several parts related to the seller’s NIP and the date of sending the document. The authorization token is a 40-character key used for secure login to the system and integration with accounting software.

When does KSeF enter into force?

The National e-Invoicing System (KSeF) will become mandatory for different groups of entrepreneurs in stages:
from 1 February 2026 for large companies with turnover above PLN 200 million per year
from 1 April 2026 for other entrepreneurs
from 1 January 2027 for the smallest companies whose sales value does not exceed PLN 10,000 per month

In addition, from 1 February 2026 all entrepreneurs will be obliged to receive invoices within KSeF.

Do I have to issue all invoices via KSeF?

Yes, when KSeF becomes mandatory, all invoices will have to be issued through this system. From the moment this obligation is implemented, it will be the only acceptable way of issuing invoices for enterprises covered by the regulations.