The amendment to the law regarding the National e-Invoicing System (KSeF) introduces significant changes, including the new FA(3) structure, aimed at simplifying the implementation of mandatory electronic invoicing. These changes stem from public consultations conducted by the Ministry of Finance with entrepreneurs between February and July 2024, which aimed to identify key technical and business needs and challenges.
In the first article, we outlined the most important aspects of the mandatory KSeF. In this article, we focus specifically on the differences in the new FA(3) invoice structure, which now includes the option of attaching invoice attachments, and the impact this will have on SAP systems.
The New FA(3) Structure – Invoice Attachment
One of the key technical changes in the new FA(3) structure is the expansion of the FA(3) invoice schema to include a new, optional “Attachment” node. This feature responds primarily to requests from utility providers (electricity, gas), telecommunications, and fuel suppliers who need to send detailed data about the services provided.
The new “Attachment” node allows detailed information to be added to invoices, such as unit prices, quantities of goods/services, energy or gas consumption data, and specifics regarding individual utility pickup points.
The attachment structure is designed to be universal, allowing taxpayers to adapt it to the specifics of their industry by defining the content of individual fields themselves.
Attachments will consist of data blocks. Each taxpayer can decide whether to use this functionality, as including attachments will be voluntary.
Implementing Attachments in the New FA(3) Structure – Technical Aspects
Sending attachments to KSeF will require prior notification via the KSeF API. This notification will be automatically verified, speeding up the activation of the feature. To ensure data quality, attachments must meet specific technical standards. This means that integrating this feature will require changes to taxpayers’ invoicing software, including SAP. Unfortunately, not every file type will be allowed as an attachment.
This is essentially the biggest structural difference between FA(2) and FA(3). More details about attachments in KSeF can be found in our article on the concept of e-invoice attachments in KSeF.
Voluntary Use and Scope
The new attachment functionality will not be mandatory. Companies can decide independently whether to implement attachments, depending on their operational needs. Although the solution was initially designed for the energy, telecommunications, and fuel industries, no sectoral restrictions are introduced.
Certificates and Offline Mode
A notable facilitation in handling the new solution is the ability to pre-generate QR code certificates. Starting in November 2025, taxpayers will be able to install certificates needed to issue invoices in case of KSeF failures or unavailability. You can follow the situation at this link.
An important technical aspect is also the implementation of a voluntary “offline” mode, allowing taxpayers to issue electronic invoices without immediate connection to KSeF, while still being required to send those invoices to the system on the next working day.
Aligning the KSeF Environment with the New FA(3) Structure
In the 4th quarter of 2025, the production environment of the mandatory KSeF will be implemented, replacing the current voluntary system. This change will allow taxpayers to familiarize themselves in advance with the target functionalities, significantly facilitating the new system’s implementation.
Identification Data and NIP Obligations
Changes also affect identification obligations. The buyer’s NIP (Tax Identification Number) will be mandatory on the invoice if the buyer is VAT-exempt but not registered in the electronic VAT taxpayer list.
The amendment to the VAT Act, enabling the transition to FA(3), is currently under review, with the last update dated November 5, 2024. All indications suggest that the bill will be submitted to the parliament during or shortly after the summer holidays — now it remains to wait for the outcome of this legislative process.
