KSeF (National e-Invoicing System) is a groundbreaking solution in the Polish tax system that has fundamentally changed how invoices are issued and circulated in Poland. It is a nationwide IT system run by the Head of KAS (National Revenue Administration) (Article 106nd of the VAT Act), used to issue, receive and store structured invoices. Since 1 February 2026 its use has been mandatory – in stages, with transitional exceptions until 31 December 2026.
KSeF aims not only to simplify the flow of documents between businesses, but also to improve tax control and automate settlements. For businesses, this means adapting accounting systems to new requirements, but also the chance to benefit from digitalised invoicing processes.
The National e-Invoicing System is mandatory for VAT taxpayers – both active and exempt – with a registered office or fixed establishment in Poland, subject to the exceptions in Article 106ga(2) of the VAT Act. The system allows structured invoices to be issued, sent, received and stored in a single electronic format
KSeF is particularly important for accounting offices, which have to handle new processes related to the electronic flow of documents. Choosing the right IT tools is key to providing accounting services smoothly.
KSeF implementation timeline - key dates
The obligation to use the National e-Invoicing System was introduced in stages so that businesses could gradually adapt to the new requirements. The timeline reflects the different scale of business activity (Articles 145l and 145m of the VAT Act).
The first stage started on 1 February 2026 and concerned the largest businesses. The obligation to issue invoices in KSeF then covered taxpayers whose total sales including tax exceeded PLN 200 million in 2024. From the same day, all taxpayers receive structured invoices through KSeF – including those who could still issue their own invoices outside the system.
The first stage of the obligation to issue invoices in KSeF from 1 February 2026 concerned taxpayers with sales (including VAT) above PLN 200 million in 2024. These businesses were the first to use the system at full production scale
The second, much broader stage started on 1 April 2026 and covered all other taxpayers required to issue structured invoices. Until 31 December 2026, the smallest businesses may still issue electronic or paper invoices outside KSeF if the value of sales (including tax) documented with such invoices in a given month does not exceed PLN 10,000 – they lose this right from the invoice with which they exceed the limit (Article 145m). Until the end of 2026, invoices issued using cash registers may also be issued outside KSeF (Article 145n).
Until 31 January 2026 the system was voluntary, which gave businesses the chance to become familiar with its functions in advance. Businesses that use the transitional exceptions can today start issuing invoices in KSeF early in the same way – gradually introducing processes, testing integration with accounting systems and training staff before 1 January 2027.
- Analyse your current invoicing processes
- Choose suitable software integrated with KSeF
- Test the integration with the system
- Train staff to use the new tools
- Introduce data security procedures
- Prepare backups and contingency plans
- Run a pilot test period
Penalties for invoices outside KSeF – from 1 January 2027
An important element of the transitional period is the absence of financial penalties throughout 2026: the penalties under Article 106ni of the VAT Act (up to 100% of the tax shown on an invoice issued outside KSeF, or up to 18.7% of the total amount due on an invoice without VAT) apply from 1 January 2027. The obligation to issue invoices in KSeF itself, however, has applied since 2026, and failing to meet it does not lead to fiscal criminal proceedings (Article 106ni(4)).
Scope of KSeF - who must use the system
The National e-Invoicing System is mandatory for a wide group of taxpayers, but the law also provides important exceptions (Article 106ga(2) of the VAT Act). The main group covered by the obligation are VAT taxpayers, both active and exempt, who conduct business in the Republic of Poland.
However, the legislator provided a number of exceptions to the obligation to use KSeF, which concern specific business and legal situations. The first important exception concerns taxpayers who have neither a registered office nor a fixed establishment in Poland. This rule excludes from the obligation entities that conduct their business outside the country.
Taxpayers with no registered office and no fixed establishment in Poland, as well as invoices under the special VAT schemes, are excluded from the obligation to issue invoices in KSeF. The exclusion also covers invoices for individuals not running a business – such invoices may, however, be issued in KSeF voluntarily and made available to the buyer in an agreed way (Article 106ga(4), Article 106gb(4))
Another exception concerns taxpayers who do not have a registered office in Poland but do have a fixed establishment in the country. In this case, the exclusion applies only if that fixed establishment does not take part in the supply of goods or services to which the invoice relates.
The exclusion also covers invoices issued by taxpayers using the special schemes set out in Section XII, Chapters 7, 7a and 9 of the VAT Act – documenting transactions settled under those schemes. These are: the non-Union scheme for certain services, the scheme for international occasional road passenger transport and the import scheme (distance sales of imported goods).
- Taxpayers without a registered office in Poland (and without a fixed establishment taking part in the sale)
- Entities using special VAT schemes (Chapters 7, 7a and 9)
- Invoices for individuals not running a business
- Taxpayers from other EU countries using the SME scheme exemption in Poland (Article 113a)
- Appropriately documented supplies specified in the regulation issued under Article 106s of the VAT Act
In addition, invoices issued to buyers who are individuals not running a business are excluded from the obligation – the same taxpayer still issues invoices for businesses in KSeF. This exclusion is of practical importance for businesses selling at retail or providing services to individual consumers.
Benefits of early KSeF adoption
To encourage businesses to use the National e-Invoicing System voluntarily before the obligation was introduced, the Ministry of Finance provided a package of incentives. Since 1 February 2026 these benefits are no longer a privilege of voluntary users – they follow from the general rules and apply to invoices issued in KSeF.
One of the most important benefits is not having to store invoices yourself. Invoices sent to KSeF are stored in the system for 10 years from the end of the year in which they were issued (Article 112aa of the VAT Act), which means savings on IT infrastructure and the cost of physically storing documents. This benefit is particularly important for small and medium-sized businesses. Invoices issued outside KSeF (for example to consumers or under the transitional exceptions) must still be stored by the business itself (Article 112a).
Before 1 February 2026, voluntary KSeF users received VAT refunds within 40 days instead of 60 and did not have to store KSeF invoices themselves. Since 1 February 2026, the basic VAT refund period has been 40 days for everyone (Article 87(2)), and KSeF invoices are stored by the system
Another benefit is that invoices from KSeF do not have to be provided in a JPK_FA file at the request of the tax authorities (Article 193a § 1a of the Tax Ordinance Act (Ordynacja podatkowa)). Because invoices are available in KSeF in structured form, the tax authorities have direct access to them, which reduces the need for additional action by the business.
Until 31 January 2026, a particularly attractive incentive was the reduction of the VAT refund period from the standard 60 days to 40 days. Since 1 February 2026, 40 days has been the basic period for all taxpayers, which directly affects the liquidity of businesses, especially those that regularly claim an excess of input VAT over output VAT.
| Benefit | Before KSeF | After KSeF | Saving |
|---|---|---|---|
| VAT refund period | 60 days | 40 days | 20 days |
| Invoice archiving | Business's obligation | In KSeF for 10 years | Lower storage costs |
| Providing JPK_FA | On the tax office's request | Not applicable to KSeF invoices | Time and resources |
| Legal certainty | Disputes about delivery | Single format, receipt date from KSeF | Lower risk of disputes |
The system also offers greater certainty thanks to a single electronic invoice format for all taxpayers. This reduces the risk of a buyer disputing receipt of an invoice – the invoice is received on the day its KSeF number is assigned (Article 106na(3) of the VAT Act). Sending documents in real time also streamlines business processes, especially when issuing corrective invoices (correction notes were abolished from 1 February 2026).
A higher level of automation in invoicing and bookkeeping can shorten the time needed for settlements and reduce the risk of errors when issuing documents. For accounting offices, this means the ability to serve clients more efficiently.
Example: an electronics trading company that adopted KSeF early reduced the time spent handling invoices and put their storage in order. In addition, thanks to the shorter VAT refund period, the company's liquidity improved.
The role of accounting offices in the KSeF ecosystem
Accounting offices play an important role in how the National e-Invoicing System works, even though formal responsibility for issuing invoices correctly and in compliance with the law lies with the taxpayer. Accounting offices support clients in organising the flow of invoices and meeting the new obligations – to the extent the client grants them permissions.
A key part of preparing an accounting office to work with KSeF is having the right IT tools. If the office offers its clients a system for issuing invoices, it should make sure that this tool is fully integrated with the National e-Invoicing System. Such integration allows not only compliant sending of documents, but also their automatic download and archiving.
Accounting offices can work with clients in KSeF under four access models. Each model means a different way of granting permissions to the system (regulation Dz.U. 2025 item 1815, § 3) and a different level of the office's involvement in invoicing
In practice, four models of cooperation between an accounting office and a client in KSeF are used, based on the permissions in the regulation of the Minister of Finance and Economy of 12 December 2025. This allows the way of working to be tailored to the specific business relationship and the preferences of both parties.
In the first model, the client does not give the accounting office any access to KSeF. In this case, the office has no direct view of the invoices in the system and receives them from the client through other channels, for example as XML files downloaded from KSeF, invoice visualisations with a QR code or traditional ways of passing on documents. This model may be preferred by clients who want to keep full control over their data in KSeF. In the second model, the client grants the KSeF permission directly to the accounting office as a designated entity (identified by its NIP (tax identification number), § 3(3) of the regulation). This solution is particularly practical for larger accounting offices that serve many clients and need regular access to documents.
- No-access model - the office receives documents outside KSeF
- Entity access model - permissions for the office based on its NIP
- Personal access model - permissions for the office owner as an individual
- Employee access model - permissions for a selected office employee
The third model grants KSeF access to the owner of the accounting office as an individual. This may suit smaller offices where the owner personally handles clients and wants direct access to their documents.
The fourth model grants access to a selected employee of the accounting office. This option may be the best choice where a specific employee is responsible for a given client and should have direct access to their documents in KSeF.
Technical requirements for accounting systems
Using the National e-Invoicing System effectively requires suitable accounting software that can provide full integration with the government system. Good software should allow structured invoices to be issued and received directly, without external platforms or additional tools.
A key element of such a system is the ability to send sales invoices to KSeF automatically, directly from the accounting program. Once integration is switched on, invoices issued in the system should be passed to KSeF automatically, while the user should be able to use a draft invoice that is sent to the government system only after approval.
Modern accounting systems integrated with KSeF allow purchase invoices to be imported automatically and Official Acknowledgements of Receipt to be downloaded. These processes can be fully automated and run without user intervention
Equally important is the automatic import of purchase invoices from KSeF. The accounting system should allow expenses to be downloaded directly from the KSeF database, ideally automatically, for example once a day at night, without user intervention. This function significantly streamlines the booking of cost documents and reduces the risk of missing invoices.
Another essential function is the ability to download the Official Acknowledgement of Receipt (UPO) directly from the accounting system. After KSeF has processed an invoice, the user should be able to download the UPO, which is formal confirmation that the document was correctly delivered to the government system.
- Direct integration with the KSeF API without additional tools
- Automatic sending of sales invoices to the government system
- Draft invoice function before final approval
- Automatic import of purchase invoices from the KSeF database
- Downloading the UPO as confirmation of delivery
- Support for different structured invoice formats
- Document archiving in line with legal requirements
For accounting offices, a function that lets clients view invoices downloaded from KSeF in a client panel and approve them is particularly important. This lets the accountant easily see which documents have been approved for booking, which significantly improves work organisation and communication with clients. The data such an invoice contains follows the schema described in our article on the KSeF FA(3) structure and changes for businesses.
The system should also offer flexible testing options, such as a free trial period for businesses or special packages for accounting offices, which allow all functions to be tested thoroughly before deciding on permanent implementation.
KSeF 2.0 and the FA(3) structure – integration requirements
Integration with KSeF requires businesses to adapt their IT systems to new technical standards. Understanding the API requirements and the FA(3) data structure is key. Basic technical requirements:
- Compatibility with the KSeF 2.0 API
- Implementation of the FA(3) logical structure
- Data transmission security
- User authentication mechanisms
- Backup and data recovery procedures
- Monitoring and logging of operations
Accounting software vendors prepared their solutions to work with KSeF 2.0 and continue to develop them. Businesses that do not yet issue invoices in KSeF should contact their software vendors to find out about updates and the cost of adapting their systems. Businesses using their own IT solutions must prepare the KSeF integration themselves. This may require hiring additional IT specialists or using external technology companies.
Issuing an invoice in an integrated system
Issuing an invoice in a system integrated with KSeF is designed to be as intuitive as possible and not to require complicated steps from the user. The process consists of several key stages that ensure both legal compliance and ease of use.
The first step is a one-off configuration of the KSeF integration in the accounting program's settings. This requires authentication and authorisation of access to the government platform, but it happens only once, when the system is first configured. After successful integration, all subsequent operations run automatically.
Issuing an invoice in an integrated system requires a one-off configuration of the connection with KSeF. After this configuration, invoices are sent to the government system automatically once the sending option is selected
The invoice itself is issued in the standard way - the user enters all required transaction data, such as buyer details, a description of the goods or services, net and gross amounts and VAT rates. Modern systems also offer automatic completion of data based on previously entered information about trading partners.
The key moment in the process is choosing how to finalise the invoice. The user can save the invoice as a draft, which allows corrections to be made later, or choose to send the document to KSeF straight away. This flexibility is particularly important for complex transactions that may need additional checking before final approval.
Example: a small accounting office serving 50 clients reduced the time spent handling invoices after implementing a system integrated with KSeF. Automating the issuing and receiving of invoices made it possible to shift resources to work of greater value to clients.
A structured invoice is deemed issued on the day it is sent to KSeF (Article 106na(1) of the VAT Act). Once accepted by the system, the invoice receives a KSeF number, which is a unique identifier of the document across the whole system, and the buyer receives it on the day that number is assigned (Article 106na(3)). The number is saved automatically in the accounting system – it is given, among other places, on a corrective invoice and in the JPK_V7 (VAT return with records, SAF-T file).
For accounting offices, the client panel function is particularly important: clients can view invoices downloaded from KSeF and approve them for booking. The accountant is informed which documents have been approved, which allows bookkeeping to be kept systematic and orderly with a lower risk of missing any document.
Offline mode – the deadline for sending an invoice to KSeF
There is no general "24-hour" deadline in the law for registering an invoice – a structured invoice is issued in KSeF. A deadline for sending an invoice issued outside the system later applies only in special situations. In offline mode, the invoice must be sent to KSeF no later than the next working day after the day it was issued (Article 106nda(2)). An invoice issued in offline mode (using the FA(3) template) keeps the issue date shown on the invoice (Article 106nda(10)), but it must be sent to the system within the required deadline. The deadlines for KSeF unavailability and failure are described below, in the section on security.
Businesses must remember to ensure the continuity of their IT systems. A failure of your own system does not release you from your obligations: an invoice issued in offline mode must be sent to KSeF no later than the next working day after the day it was issued (Article 106nda(2))
Security and archiving in KSeF
The National e-Invoicing System was designed with high IT security standards and the legal requirements for storing invoices in mind. Under the law, KSeF ensures the authenticity of origin, integrity of content and legibility of a structured invoice (Article 106m(1) of the VAT Act).
One of the key benefits of KSeF is that the system takes over invoice storage: invoices sent to KSeF are stored there for 10 years from the end of the year in which they were issued (Article 112aa(1)). Businesses therefore do not have to organise their own infrastructure to store these invoices. If the 10 years expire before the tax liability becomes time-barred, the invoice must be stored outside KSeF until the end of the limitation period (Article 112aa(2)).
KSeF stores invoices for 10 years from the end of the year in which they were issued, in line with Article 112aa of the VAT Act. The system reduces the risk of losing documents and gives authorised entities access to invoices throughout that period
Data security in KSeF is based on several levels of protection, including encrypted transmission. Only authenticated entities with the relevant permissions have access to invoices (Article 106nb), and without authentication access is possible only to a specific invoice via a QR code and data identifying it (Article 106gb(3)). Permissions are granted under regulation Dz.U. 2025 item 1815, and tokens can be used only until 31 December 2026.
Particular attention was paid to document integrity: an invoice accepted by KSeF cannot be changed – errors are corrected only with a corrective invoice. Each invoice receives a KSeF number, and its data can be verified in the system, including with the QR code placed on the invoice visualisation (Article 106gb(5)).
The system also has backup and data recovery mechanisms intended to keep documents available even in the event of a technical failure. For a KSeF failure or unavailability, the law provides separate procedures: invoices are then issued using the template and sent to KSeF later – within 7 working days of the end of a failure announced in a communication, or on the next working day after a period of unavailability (Article 106nf(4), Article 106nh(2)).
It is also important for system users that KSeF is subject to the GDPR rules on personal data protection, and that the controller of the data in the system is the Head of KAS (Article 106nd(1)).
The new KSeF e-invoicing system compared with previous invoicing
Alongside simplifying the flow of documents, more effective action against VAT fraud is another important aim of the reform. Centralising invoices in one system allows the tax administration to monitor business turnover better and detect irregularities faster. KSeF is also used to analyse and check the correctness of invoice data (Article 106nd(2)(9)), which makes it easier to compare sales and purchase invoices. Checking an invoice against the template in KSeF helps catch some irregularities already at the time of issue.
| Aspect | Previous system | New KSeF system |
|---|---|---|
| Invoice registration | Voluntary | Mandatory (with the exceptions in Article 106ga(2)) |
| Registration deadline | No set deadline | Issued in KSeF; offline - by the next working day |
| VAT refund | 60 days | 40 days |
| State control | Limited | Ongoing access to invoice data |
| Implementation costs | Minimal | Significant at the start |
| System integration | Optional | Required |
Legal basis of KSeF - the VAT Act and the regulation
Introducing KSeF required the Sejm to pass legislation and the President to sign it. The legislative process has been completed: the provisions of the VAT Act apply (consolidated text Dz.U. 2026 item 1263), introduced by the acts of 16 June 2023 (Dz.U. 2023 item 1598) and 5 August 2025 (Dz.U. 2025 item 1203), together with the regulation on the use of KSeF (Dz.U. 2025 item 1815).
Key legal aspects of the new system:
- The obligation to issue structured invoices in KSeF (Article 106ga)
- Sanctions for failing to meet e-invoicing obligations (Article 106ni, from 1 January 2027)
- Transitional provisions for different groups of businesses (Articles 145l–145n)
- Personal data protection rules
- Rules on access to information in KSeF
- Appeal procedures in the event of disputes
Another important legal aspect is the protection of commercial data and confidential information. KSeF collects detailed information about business transactions, which raises concerns among some businesses about preserving trade secrets. Who has access to invoices, and to what extent, is set out in the rules on permissions (Article 106nb of the VAT Act and regulation Dz.U. 2025 item 1815).
Preparations by the Ministry of Finance and KSeF 2.0
The Ministry of Finance carried out preparations for the full implementation of the National e-Invoicing System. The action plan covered both technical and educational aspects intended to ensure a smooth transition to the new system.
Preparation timeline (according to ksef.podatki.gov.pl):
- June 2025 - publication of the KSeF 2.0 API technical documentation and the target FA(3) logical structure (30 June 2025)
- August 2025 - adoption of the VAT Act amendment of 5 August 2025 (Dz.U. 2025 item 1203)
- September 2025 - launch of open API testing for integrators and businesses (30 September 2025)
- November 2025 - launch of the Certificates and Permissions Module (1 November) and the KSeF 2.0 Taxpayer Application in the test and pre-production environments (3 and 15 November)
The KSeF 2.0 API technical documentation and the FA(3) logical structure were crucial for integrators and accounting software vendors. Publishing these documents in June 2025 gave technology companies about seven months to prepare their solutions
The Ministry ran educational activities for different audiences, including the free training and webinar series "Środy z KSeF" ("KSeF Wednesdays", from 24 September to mid-December 2025). Particular emphasis was placed on supporting accountants and accounting offices, which play a key role in helping businesses implement the changes.
Open API testing, which started on 30 September 2025, made it possible to check the system's functions in practice in near-real conditions, and from 15 October 2025 the pre-production (Demo) environment was available. The smallest businesses that use the transitional exception until the end of 2026 can use free tools from the Ministry of Finance (such as the KSeF 2.0 Taxpayer Application) and the information materials on ksef.podatki.gov.pl.
Example of preparations in a medium-sized trading company: a business selling building materials wholesale with an annual turnover of PLN 50 million started preparing for KSeF back in 2024. The company updated its ERP system, trained its accounting team and ran integration tests in the KSeF test environment. Thanks to its early preparations, implementing KSeF from 1 April 2026 went without major problems.
E-invoicing in other countries
Poland is not the first country to introduce mandatory e-invoicing. Other countries' experience can be a valuable lesson for Polish businesses and regulators.
Examples of e-invoicing systems in other countries:
- Italy - the FatturaPA system has applied to B2B transactions since 2019
- Spain - mandatory B2B e-invoicing is provided for in the Crea y Crece Act of 2022; the dates depend on implementing regulations
- France - since 1 September 2026 all businesses must accept e-invoices, and the obligation to issue them is being phased in until 2027
- Brazil - one of the oldest e-invoicing systems in the world
- Mexico - the comprehensive CFDI system has operated for many years
Other countries' experience shows that the biggest challenges arise in the first months after a system is introduced. Providing appropriate technical and educational support to businesses during that period is key
An analysis of international experience points to several key success factors:
- A sufficiently long preparation period for businesses
- Intensive educational and training activities
- System flexibility allowing integration with different solutions
- Effective technical support in the first months of operation
- Gradual introduction without drastic penalties at the start
