A digital revolution with barriers. KSeF limitations
The limitations of the KSeF system pose significant challenges in the implementation of the National e-Invoicing System (KSeF) in Poland. KSeF is a key element in the digitalization of tax processes in the country. Its goal is to simplify and standardize the circulation of invoices through the mandatory use of structured invoices. While this concept offers many benefits, its implementation encounters numerous technical and organizational limitations, especially on the side of the Ministry of Finance (MF).
For companies using ERP systems such as SAP, integration with KSeF presents a serious challenge. This article analyzes those limitations and provides practical recommendations for businesses preparing for the mandatory implementation of KSeF.
Key KSeF limitations on the MF side
1. Lack of flexibility for industry-specific needs
KSeF was designed with a standardized invoicing process in mind, which can be a limitation for industries with specific requirements. For instance, companies in the energy, telecommunications, or transport sectors may require additional functionalities, such as handling extensive attachment data.
Although the Ministry of Finance has announced development plans in this area and intends to introduce simple attachments, there is still much work to be done.
2. Technical issues
Implementing such a complex IT system involves risks of errors and technical problems, including:
- KSeF system unavailability during overload or failure.
- Lack of support for offline mode in many cases, which can be problematic for businesses operating in areas with limited internet access.
- Delays in updates and the rollout of new features due to extended decision-making processes within the MF (already visible).
3. Limited API development capabilities
The KSeF API, although a fundamental integration tool, has its limitations:
- The technical documentation and error code descriptions are insufficient.
- Integration with some older ERP systems is complex.
- There is no unified invoice visualization accessible via API.
- API response times may be too long during peak usage periods, creating a domino effect and overloading the system.
4. Time limitations of implementation
For many companies, implementing KSeF means quickly adapting internal processes and IT tools. However, the MF’s implementation schedule has been criticized for:
- Very short transitional periods (e.g., two months between large and small companies).
- No gradual rollout for smaller entities, which may struggle to adapt quickly.
- Not taking into account older entrepreneurs who previously only issued paper invoices.
5. Lack of support for microenterprises
Smaller companies, especially those without advanced IT systems, may face difficulties operating KSeF. While the MF has provided a taxpayer application, its features are limited and do not always meet the needs of such entities.
Integrating KSeF with SAP: Technical and organizational challenges
1. SAP system update requirement
Integration with KSeF requires that the SAP system be properly updated. Older versions may not support necessary functionalities, leading to costly updates or migrations.
2. Security and authentication
Data exchange with KSeF must be secure. SAP must include SSL authentication mechanisms, NIP-number-specific tokens, and ensure proper encryption of transmitted data.
3. Data mapping and invoice structure
KSeF requires invoices to be submitted in a specific XML format, compliant with the FA(3) structure. SAP must be capable of generating invoices in this format, which may require changes to existing processes and data structures. More information on the website of the National e-Invoice System.
4. Handling return messages
After an invoice is submitted to KSeF, the SAP system must be able to handle return messages, such as confirmations or error notices, and retrieve UPO.
This requires implementing appropriate monitoring and error-handling mechanisms, and most importantly, user notifications in cases where the invoice is rejected by KSeF.
5. Staff training
Implementing KSeF entails training staff responsible for operating the SAP system. Employees need to be aware of the new processes and procedures related to issuing and sending invoices.
KSeF system limitations on the MF side – common mistakes and recommendations
Mistakes:
- Lack of proper planning and implementation timeline – many companies underestimate the time required for full SAP-KSeF integration. Implementation in a large organization may take 2–3 months.
- Skipping integration testing – without a sandbox environment, production errors are likely. Unfortunately, many companies don’t refresh their test environments regularly.
- Late implementation of FA(3) structure changes – outdated data mappings result in rejected invoices, or worse, accepted invoices with incorrect data (KSeF only checks the format, not content).
- Insufficient training of finance and IT teams – this leads to misinterpretation of KSeF messages (e.g., code 100 does not mean that the invoice has been accepted, but that its processing has started).
- Not updating ERP systems – older SAP versions may not support KSeF technical requirements (e.g., minimum required SSL protocol level).
Recommendations:
- Phased implementation – start with invoice process analysis and audits, then plan a pilot project.
- Use certified SAP partner tools – ensure compliance with FA(3) specification.
- Testing in KSeF test environment – helps detect errors before going live.
- Regular updates – for both SAP and any intermediary software.
- Ongoing training – boosts the competence of accounting and technical teams.
FA(3) structure – what you need to know
A key aspect of SAP-KSeF integration is compliance with the FA(3) logical structure. This is a new format that replaces earlier versions and introduces major changes:
- More detailed data required in the XML.
- New requirements for buyer and seller identifiers.
- Mandatory fields that did not previously exist (e.g., payment data and delivery terms).
You can find a full description of the changes in our dedicated article:
The latest changes in KSeF – the new FA(3) logical structure
KSeF is undoubtedly the future of Polish e-invoicing, but its successful implementation requires preparation, investment, and expert knowledge.
The limitations of the KSeF system on the Ministry of Finance’s side – such as inflexible APIs, system availability issues, and lack of clear XML visualizations – can generate real costs and risks for business continuity.
If your company uses SAP and is planning to integrate with KSeF – take advantage of the knowledge and experience of Haergi experts. We assist in analysis and full integration, ensuring compliance with legal requirements and process security.
Contact us today to see how we can streamline your KSeF implementation in SAP!
