Integration with the National e‑Invoicing System (KSeF) in banking: a practical approach to attachment handling

Business context

The National e‑Invoicing System (KSeF) is designed to enable the centralized preparation, transmission, receipt, and storage of electronic invoices, simplifying document workflows and increasing transparency in tax settlements. However, the system supports only structured text data and does not allow the transmission of supplementary files.

As a result, many organizations needed an additional solution to complement KSeF. In practice, this meant creating tools that not only support attachments but also eliminate issues caused by the lack of standardization, such as manual file transfers or the risk of documentation errors. Consdata supported one of the banks in addressing these challenges by using the Eximee low-code development platform to build a solution that efficiently extended KSeF’s capabilities and streamlined the entire attachment‑handling process.

Project execution

The project began with a detailed analysis of regulatory and technical requirements related to attachment handling in KSeF. The team had to consider both the limitations of the government system and the needs of users who work with supplementary documents on a day-to-day basis.

Based on this analysis, the integration architecture was designed. It included mechanisms for sending and receiving attachments, as well as backend verification of invoice numbers and gross amounts through communication with the government API. This connection enables the retrieval of invoice data from KSeF. As a result, bank customers gained the ability to attach files both to invoices already present in KSeF and to those being submitted to the system for the first time. Additionally, a key stage of the project was the introduction of a simple, no‑login form for adding attachments. Built on the Eximee platform, it allowed the team to quickly deliver an intuitive interface and flexible document‑handling processes.

All processes were designed to ensure data security and consistency while maintaining ease of use. Development was performed internally by the bank, while Consdata, as the technology partner, supported the project in the area of business analysis.

Challenges

The project involved several organizational, regulatory, and technological challenges.

• Organizational challenges were primarily associated with preparing employees for the new way of handling invoices with attachments. This required training and updates to operational procedures to ensure smooth, compliant daily work with documents.
• Regulatory challenges stemmed from the need to align the solution with the requirements of the Ministry of Finance, which define the formats, data scope, and methods of transmitting information to KSeF. Ensuring full compliance was essential for the system to operate without risks or irregularities.
• Technological challenges proved to be the most complex. They included ensuring the security of transmitted files, supporting multiple attachment types, validating and archiving them, and integrating with KSeF services to verify invoice data. All these components had to be combined into a coherent, stable, and intuitive process.

Each of these areas required precision and close cooperation between teams responsible for business processes, security, and system development.

Benefits

The most significant improvement resulting from the implemented project is the bank’s ability to maintain a complete document workflow: invoices and all related files are now stored within one unified system. This makes accounting and tax processes more transparent and reduces the risk of missing documentation.

Full document availability also increases transparency for tax authorities, which can verify data completeness more quickly and easily. This, in turn, reduces the number of inquiries and corrections, improving communication between institutions.

From the customer perspective, everyday tasks have become simpler. Customers can attach files—such as scans, specifications, itemized lists, or transaction confirmations—without switching between different tools, and the no‑login form makes the entire process fast, intuitive, and accessible even to external users.

Conclusions and future implications

Although the integration with KSeF for attachment handling was initially only intended to meet immediate regulatory requirements, it has also become an important step toward broader digitalization of financial processes. Full digital document workflow now includes not only invoices but also all supporting materials essential for accurate transaction settlement.

The implemented solution paves the way for further enhancements, such as advanced attachment archiving, search, or reporting—features that can significantly improve the work of accounting and operations teams. Importantly, this functionality addresses real customer needs, providing access to all supplementary documents within one organized system.

As a result, the bank can now offer more comprehensive and user‑friendly services than standard KSeF integration alone, strengthening its position as an institution actively supporting the digital transformation of financial processes.