What Is a Structured Invoice in KSeF? What Distinguishes an E-Invoice and How Is It Issued in the National e-Invoicing System (KSeF) 2.0 and Circulated as a VAT Document Between the Issuer and the Buyer in Poland?

What Is the National e-Invoicing System (KSeF), How Does It Work in Practice, and Why Will E-Invoicing Become the Standard in Poland?

KSeF (the National e-Invoicing System) is a nationwide ICT platform in Poland that introduces a uniform standard for documenting business transactions. E-invoicing will become the standard primarily due to a statutory obligation to use structured invoices, which will enter into force according to the following schedule:

• 1 February 2026 – for large enterprises operating in Poland whose sales revenue in 2024 exceeded PLN 200 million;
• 1 April 2026 – for all other VAT taxpayers in Poland, subject to certain exceptions for which the obligation will apply from 1 January 2027.

It is important to note that the obligation to receive invoices via KSeF will apply to all taxpayers in Poland as of 1 February 2026, regardless of when they themselves become required to issue sales invoices through the KSeF system.

What Information Does a Structured Invoice Contain and How Does It Differ from a Traditional PDF Invoice?

Unlike a PDF invoice, which is merely an electronic image of a document, a structured invoice used in Poland’s KSeF system consists of a set of raw data stored in an XML file. Its “framework” is composed of several defined sections, including in particular:

• Header
  the technical metadata of the file.
• Entity 1 and Entity 2
  the identification details of the seller and the buyer, as required under Polish VAT regulations.
• FA
  the so-called core of the invoice, containing transaction details, taxable amounts, and applicable VAT rates.
• Attachment
  a new, optional section introduced in the FA(3) schema, enabling the transmission of complex data (e.g. utility tariffs). This functionality is available after prior notification to the Polish tax authority via the e-Tax Office (e-Urząd Skarbowy) platform.

The KSeF system in Poland does not accept attachments as separate PDF or JPG files. All invoice-related data must be embedded directly within the XML structure of the structured invoice.

Issuing an Invoice in KSeF – How Can Taxpayers and Businesses Issue Structured Invoices in Poland?

Structured invoices in Poland may be issued manually using tools such as the KSeF Taxpayer Application, the KSeF mobile application, or the e-Microbusiness platform, or in a more automated manner via a sales or ERP system integrated with KSeF through the KSeF 2.0 API.

The process of issuing a structured invoice is multi-stage and independent of the software used:

1. Authorisation verification
   The seller must have the right to issue invoices on behalf of the taxpayer. In the case of a sole trader operating in Poland, such authorisation is granted automatically. For companies and partnerships, the relevant permissions must be formally assigned.
2. Authentication
   Access to KSeF is obtained via a Trusted Profile (Profil Zaufany), a qualified electronic signature, an electronic seal, or—when operating from a sales system—via a KSeF certificate or authentication token.
3. Data entry
   Invoice data must be entered in accordance with the official XML schema (e.g. field P_1 represents the issue date, while P_2 refers to the invoice number).
4. Submission (session)
   Invoices may be submitted either through an interactive session (single invoices) or a batch session (multiple invoices submitted together in a ZIP file).
5. Validation
   The system verifies the file’s compliance with the schema and the issuer’s authorisation. If the file contains semantic errors, it will be rejected (with a status other than 200).
6. Assignment of the KSeF number
   Upon successful validation, the invoice is assigned a unique KSeF identification number, and the issuer may download the Official Receipt Confirmation (UPO – Official Acknowledgement of Receipt).

Receiving a Structured Invoice via the National e-Invoicing System (KSeF) – How Does the Process Work in Practice?

At the moment a KSeF number is assigned, a structured invoice issued in the KSeF system is deemed to have been delivered to the buyer, provided that the buyer’s Polish tax identification number (NIP) has been indicated on the invoice. Under the mandatory KSeF regime in Poland, the recipient’s prior consent to receive an e-invoice is no longer required.

If the buyer is a foreign entity or a consumer (B2C) who does not have access to the KSeF system, the seller—despite issuing the invoice in KSeF (which is optional in B2C transactions)—is still required to provide the invoice to the buyer by another agreed method, for example as a PDF file with a QR code.

Invoice Issue Date vs. Invoice Receipt Date in KSeF – What Should Taxpayers and Buyers in Poland Pay Particular Attention To?

This is one of the most critical aspects of the Polish KSeF system, operating in two distinct “modes”:

• ONLINE mode (standard)
  The invoice issue date is the date on which the invoice is submitted to KSeF, provided that the date entered by the taxpayer in field P_1 corresponds to the submission date.
• OFFLINE mode (e.g. offline24, system failure)
  The invoice issue date is the date indicated by the taxpayer in field P_1, even if the technical submission of the XML file to KSeF takes place later (e.g. on the next business day).

Important for the buyer: In online mode, the invoice receipt date of a structured invoice is always the date on which the KSeF number is assigned. In offline or contingency mode, the receipt date may be the actual date on which the invoice is delivered to the buyer, provided that this date precedes the assignment of the KSeF number.

Note:
The KSeF system will reject the XML file if the date entered in field P_1 is a future date in relation to the moment of submission.

Structured Electronic Invoice vs. E-Invoice – Key Differences Relevant to a Company’s Financial Management in Poland

A structured electronic invoice and an e-invoice are not synonymous terms.

An e-invoice, understood as a traditional electronic invoice (e.g. in PDF format), is not assigned a KSeF number and does not have to follow a fixed data structure.

A structured invoice issued via KSeF in Poland ensures compliance with Polish tax regulations and provides automatic archiving of invoices for a period of 10 years, in line with statutory requirements.

Using the KSeF system for invoice issuance also eliminates the problem of duplicate invoices, as invoices issued through the system remain continuously available to the buyer in their original, authoritative version.

How to Use KSeF? The KSeF Taxpayer Application, System Integration, and Electronic Document Workflow

Taxpayers in Poland may use the free KSeF Taxpayer Application, which is also available as a mobile app. The application enables users to manage authorisations, generate KSeF tokens and certificates, as well as issue, receive, and view invoices within the system.

Larger entities operating in Poland should consider integrating their ERP systems with the KSeF 2.0 API, which allows for seamless automation of invoice submission and receipt directly from internal systems. It is also advisable to integrate KSeF with the company’s electronic document management or workflow system, as this significantly improves internal processes related to the collection, approval, and circulation of sales and purchase documents.

Should You Issue a Structured Invoice or a Traditional One? VAT, Formal Requirements, and the Obligation to Use KSeF in Poland

As of the date when the obligation applies to all VAT taxpayers in Poland (1 January 2027), the structured e-invoice issued via KSeF will become the only permissible form of invoicing in B2B transactions.

From that point onwards, traditional documents will remain applicable only in the following cases:

• Invoices issued to consumers (B2C) – where the use of KSeF is optional;
• Special VAT procedures (e.g. OSS, IOSS);
• Tickets serving as invoices under Polish VAT regulations.

Documents such as pro forma invoices, debit notes, or internal accounting documents are not supported by the KSeF system and will therefore continue to circulate outside KSeF.

How to Issue a Corrective Invoice in KSeF and How Does Its Circulation in the System Work?

Within the Polish KSeF system, corrective notes and the possibility of cancelling an invoice no longer exist. Any error—including an incorrect buyer’s NIP (Polish tax identification number)—requires the issuance of a corrective invoice.

Rules for issuing corrective invoices in KSeF in Poland:

• The KSeF number of the corrected invoice must be mandatory indicated in the corrective invoice (provided that the original invoice was issued via KSeF).
• The net, VAT, and gross amounts in the summary of the correction must be entered as differences in relation to the original invoice.
• A corrective invoice undergoes the same validation process as the original invoice and is made available to the buyer in real time once its KSeF number has been assigned.

An Invoice Issued via KSeF – What Should Every Entity in Poland Know Before the Full Implementation of KSeF 2.0?

Before full implementation, businesses operating in Poland should conduct an internal process audit and select appropriate tools to support invoicing and document circulation.

For a successful implementation, it is crucial to understand that KSeF verifies only the technical structure of the file, not the substantive or arithmetic correctness of the invoice content. An incorrectly calculated amount that passes XML validation will enter legal circulation and will require a formal corrective invoice. Attention should also be paid to the transitional provisions: if a taxable transaction took place in January 2026, but the invoice is issued on 1 February 2026 or later, it must be issued via KSeF.

Businesses receiving purchase invoices through KSeF should be aware that the system may contain invoices incorrectly issued to their company, whether by mistake or as a result of fraudulent activity. It is therefore necessary to implement procedures for substantive verification and approval of purchase invoices, in order to mitigate the risk of fraud.

It is also advisable to establish contingency procedures for periods of KSeF system outages or unavailability. Like any IT system, KSeF may experience temporary downtime or failures. Given its mandatory nature, a lack of preparedness may result in the disruption of key business processes on the seller’s side.