Preparing for KSeF: Challenges, Process, and the Role of a Partner

KSeF – why is this topic so important? 

The National e-Invoicing System (KSeF) is one of the most significant digitalization challenges in Polish finance in recent years. From February 1, 2026, the obligation to use KSeF will apply to the largest taxpayers (sales exceeding PLN 200 million in 2024), and from April 1, 2026, to all other entrepreneurs. “Digitally excluded” micro-enterprises will be covered by the obligation from January 1, 2027.[1],[2] 

This means that paper invoices and PDFs are becoming a thing of the past. Every sales invoice will have to be sent to the Ministry of Finance’s central system in XML format, compliant with the FA structure. Upon acceptance of the document by KSeF, a KSeF-ID is assigned, which becomes the date of issuance and receipt of the invoice. [3] 

Key challenges related to KSeF implementation 

Although the Ministry of Finance claims that the system will simplify document flow, the reality is much more complex. Implementation deadlines have been postponed several times, which shows the scale of the technical and organizational challenges. This is not a “one-click” task, but a project requiring analysis, configuration, testing, and team preparation. 

Companies must face: 

• Integration with ERP – direct connection to the KSeF API and system adaptation (e.g., Epicor Kinetic, iScala). 
• Process changes – new procedures for authorization, granting permissions, and error handling. 
• Operational risks – inability to restrict access to specific invoices, lack of department differentiation, risk of erroneous or fraudulent invoices in the system. 
• Deadlines – multiple postponements by the Ministry of Finance, illustrating the scale of the problem and uncertainty on the part of entrepreneurs. 
• Responsibility – for data accuracy, regulatory compliance, and security. 

How does KSeF work in practice? 

The system is based on clearly defined technical and procedural rules that entrepreneurs must incorporate into their solutions.Key elements include: 

• Format: invoices in XML structure compliant with the FA schema. 
• Authorization: tokens and security certificates (available from November 2025). 
• Environments: test and production (KSeF 2.0 API available for testing from September 2025). 
• Offline/emergency modes : the ability to issue invoices in case of system failure. [4] 
• Process: every invoice, after being sent to KSeF, receives a unique KSeF-ID, which becomes the date of issuance and receipt of the document. 

Most common mistakes companies make during KSeF implementation 

1. Lack of process analysis before implementation
   
   Many companies focus solely on the technical aspect of integration, ignoring the analysis of current financial procedures. This is a mistake because KSeF affects the entire document flow – from issuing invoices and corrections to reporting. Without mapping processes and identifying critical points, it is easy to fall into chaos and accounting errors.
2. Starting preparations too late
   
   Companies often postpone implementation until the “last minute,” hoping for further deadline extensions. Meanwhile, integration with KSeF requires time for configuration, testing, and team training. Delays can result in billing problems and tax risks.
3. Underestimating the impact on other systems
   
   KSeF does not operate in isolation – its implementation affects ERP, accounting, CRM, warehouse, and reporting systems. Failure to analyze dependencies can lead to disruptions in business processes, e.g., in foreign invoicing or integration with sales systems. Therefore, a holistic approach covering all related areas is necessary.

Why should you start preparing now and choose an experienced partner? 

KSeF implementation is a strategic project that affects the entire finance area of a company. Mistakes can mean chaos in billing, delays, and tax risks. That is why it is worth working with a partner who: 

• knows the specifics of ERP systems (Epicor Kinetic, iScala), 
• has experience in integrating with the KSeF API, 
• provides support in configuration, testing, and production launch. 

 Mindbox is currently carrying out KSeF implementations for over a dozen clients from various industries, which allows us to use best practices and proven scenarios.

We carry out implementations for Epicor Kinetic and iScala systems – we perform full integration with KSeF. 

KSeF implementation process at Mindbox – step by step 

At Mindbox, the process of implementing KSeF into an ERP system is carried out according to a proven, well-organized scheme that guarantees efficiency and minimizes the risk of errors. 

The main stages of implementation are: 

1. Kick-off meeting: analysis of current invoicing processes, collection of document examples. 
2. Installation and configuration: connecting ERP to the KSeF API, field mapping, data and permission configuration. 
3. Modification of existing invoice print templates – adding QR codes for online mode prints (for recipients outside KSeF, e.g., foreign entities) and in emergency mode. 
4. Obtaining access: ZAW-FA submission, granting permissions, preparing the test environment. 
5. Testing: sending a dozen or so invoices in various variants (domestic, foreign, corrective), verifying correctness. 
6. Production launch: switching to the production environment, support in the first steps, monitoring performance. 

KSeF – an obligation that can become an advantage 

Although implementation is difficult, a well-executed project paves the way for: 

• process automation, 
• better control over data, 
• preparation for further technological changes (e.g., integration with analytical tools, automatic reporting). 

In summary – early implementation allows you not only to avoid risks but also to build a competitive advantage – more efficient processes and readiness for further technological changes can become a real asset for the company. 

Enterprises that take preparatory actions now gain time to conduct tests, refine integration, and train their team. It is also an opportunity to optimize internal procedures, automate document flow, and more easily adapt to new legal and business requirements. Thanks to this, the company will not only go through the mandatory changes seamlessly but also gain a foundation for further development and innovation in the future. 

FAQ – most frequently asked questions 

Is KSeF mandatory for everyone?
Yes, from 2026 (with exceptions for micro-enterprises until 2027). 

What are the penalties for not implementing it?
The Ministry announces no penalties until the end of 2026, but sanctions will apply thereafter. 

Does KSeF replace JPK?
Yes, as a result of KSeF implementation, the obligation to submit JPK-FA will disappear, while other JPKs will of course remain, e.g., JPK-V7M (for which a new structure including KSeF-ID will come into effect). 

Does Mindbox implement KSeF only for Epicor and iScala?
Yes, currently the solution is dedicated to clients using these ERP systems. 

Bibliography:  

[1] https://www.podatki.gov.pl/wyjasnienia/obowiazkowy-ksef-odroczony-do-1-lutego-2026-r/

[2] https://www.gov.pl/web/finanse/krajowy-system-e-faktur–plan-wdrozenia

[3] https://ksiegowosc.infor.pl/7472090,ksef-wchodzi-w-zycie-w-2026-r-przewodnik-dla-przedsiebiorcow-i-ksiego.html 

[4] https://krajowysystemefaktur.pl/porady/ksef-nowy-harmonogram-wdrozenia/#