KSeF by 2026: the roll-out of electronic invoicing in Poland – what do you need to know?

The National e-Invoice System (KSeF) is a key project of the Ministry of Finance, which, from 1 February 2026, will introduce an obligation for the largest enterprises to issue structured invoices, and from 1 April 2026 will extend to all VAT taxpayers. The system aims to streamline and make economic transactions more secure through the electronic circulation of invoices, the elimination of errors and the acceleration of tax settlements. The implementation of KSeF is not only a technological change, but above all a reorganisation of business and tax processes within companies.

KSeF 2026 implementation timetable

In response to initial technical problems and numerous public consultations, the Ministry of Finance has adopted a phased approach to the implementation of KSeF, divided into two key phases:

1. 1 February 2026 – the obligation applies to businesses whose turnover in 2024 exceeded PLN 200 million (approximately 5,000 entities).
2. 1 April 2026 – the requirement extends to all other entities, including VAT-registered and VAT-exempt businesses, regardless of size.

In addition, transitional periods will remain in place until the end of 2026, including the option to issue invoices from cash registers and a deferral of the obligation to include the KSeF number in bank transfer references until 1 January 2027. On the same day, penalties for non-compliance with the new requirements will come into force.

Modern architecture and functionalities of the KSeF 2.0 system

The production version of KSeF 2.0, operational from 1 February 2026, introduces fundamental changes to the invoicing model:

• Structured invoice – a document in XML format, compliant with the new FA(3) structure, replacing the previous FA(2). It enables automatic verification of data accuracy and integration with accounting systems and JPK reporting.
• Offline24 mode – a permanent, voluntary option to issue invoices offline with a QR code, which must be submitted to KSeF by the end of the next working day, thereby ensuring the continuity of business processes even in the event of system failures.
• Invoice issuer certificate – a new authorisation token valid for 2 years, enabling the authentication and digital signing of invoices, particularly in offline modes.
• Invoice attachments – the introduction of the ability to send structured XML attachments (up to 3 MB), subject to approval by the National Revenue Administration (KAS), which meets the needs of the energy and telecommunications sectors.
• Multi-layered QR code system – enables verification of the authenticity and integrity of invoice visualisations outside the KSeF, in both online and offline modes.

System integration prior to implementation

From 30 September 2025, the KSeF 2.0 API will be available for integration testing, and from November 2025, a test version of the KSeF 2.0 Taxpayer Application will be made available. This will enable businesses and integrators to familiarise themselves with the system’s functionalities in practice and prepare their IT environments for a smooth transition to mandatory electronic invoicing.

Organisational and technical challenges of KSeF implementation

The implementation of KSeF is a complex process requiring cooperation between the accounts, IT, internal audit and management departments. Key issues include:

• Adapting accounting systems to the new FA(3) format and KSeF API support, including updating or replacing software.
• Organisation of document workflows – defining the roles responsible for issuing, approving and accessing invoices in KSeF.
• Managing permissions and security – granting access to users, managing certificates and tokens, and verifying security procedures.
• Implementation of the offline24 mode – developing contingency procedures and ensuring invoices are sent on time.
• Team training – preparing staff to use the new tools and processes.

It is also important to collaborate with the accountancy firm, which cannot always take full responsibility for ensuring invoices comply with KSeF requirements; therefore, the business owner must maintain oversight of the process.

Who is exempt from KSeF?

Despite the broad scope of the obligation, the legislator has provided for exemptions, including for:

• Passenger transport services involving ticket documentation and motorway tolls.
• Selected financial and insurance services, which are subject to separate regulations.
• Specific cases of cross-border self-invoicing where identification using a Polish tax identification number (NIP) is not possible.

For micro-enterprises (with turnover of up to 10,000 zł per month), the obligation will be deferred until the end of 2026, giving them time to adapt.

Benefits of implementing KSeF

The introduction of KSeF brings tangible operational and tax benefits:

• A reduction in the standard VAT refund period from 60 to 40 days.
• Automation and streamlining of invoice processing, eliminating errors and redundancies.
• Standardisation of invoice formats and easier integration with ERP systems.
• Reduced archiving costs and the elimination of the need to submit invoices to the authorities during audits.
• Enhanced data security and greater transparency in tax settlements.
• Strengthening businesses’ market position through compliance with current legislation.

For businesses preparing for KSeF 2026

Preparations for the implementation of KSeF should begin now to avoid time pressure and the risk of errors. The implementation of KSeF is not only a legal requirement but also an opportunity for the digital transformation of accounting and business processes, enhancing the efficiency and security of a company’s operations.

KSeF 2026 is a strategic initiative that will change the way Polish companies issue, send and store invoices. A new, phased implementation strategy and extensive public consultation have enabled the development of solutions tailored to business and technical realities. Businesses that take preparatory action today will avoid chaos and the risk of penalties, whilst also reaping tangible benefits from the automation and security of their accounting processes. Comprehensive system integration, well-thought-out process organisation and awareness of the new legal requirements are the foundations of success in the KSeF era.

Frequently asked questions

When will KSeF become mandatory for businesses?

The obligation to issue invoices via the National e-Invoice System (KSeF) will be introduced in stages from 1 February 2026 for the largest companies with a turnover exceeding 200 million PLN in 2025. From 1 April 2026, this obligation will be extended to all other businesses, both those registered for VAT and those exempt from it.

What are the main benefits of using KSeF?

KSeF saves time by automating the invoicing process, enhances the security of financial data through the centralised storage of invoices, and improves transparency and control over tax documentation. Furthermore, it facilitates integration with accounting systems and reduces the risk of errors in invoices.

Will it be possible to issue invoices in offline mode?

Yes, KSeF introduces the ‘offline24’ mode, which allows invoices to be issued without being sent to the system immediately. An invoice issued in offline mode must be sent to KSeF by the next working day at the latest, which ensures business continuity even in the event of technical issues or a lack of internet access.

What tools does the Ministry of Finance provide for using KSeF?

The Ministry of Finance offers free applications, such as the KSeF Taxpayer App and the KSeF Mobile App, which allow users to issue, view and manage invoices within the system. In addition, the KSeF 2.0 API documentation is available, which enables integration with financial and accounting systems.

Will it be compulsory to issue consumer invoices via KSeF?

No, issuing invoices to consumers via KSeF will remain voluntary. The Ministry of Finance allows them to be issued via the system, with the aim of simplifying the process, but does not oblige businesses to use KSeF for this purpose.

What are the key changes regarding the invoice issue date in KSeF?

For invoices issued via KSeF, the date of issue is deemed to be the day the invoice is sent to the system, rather than the day it is created in the accounting software. For tax purposes, the date on which the invoice is assigned a KSeF number is the binding date, which may result in two different dates appearing on the document.

What support can businesses receive during the implementation of KSeF?

Businesses can take advantage of free training sessions organised by the National Tax Administration, the National Tax Information helpline dedicated to KSeF, and support from tax office staff. In addition, consultations and educational materials are available, as well as assistance from experts and firms specialising in KSeF system implementations.