In today's digital world, businesses increasingly use electronic forms of accounting documentation. E-invoices are a key part of this transformation, offering many benefits in terms of efficiency, savings and automation of business processes. The introduction of KSeF (National e-Invoicing System) has significantly changed how electronic invoices are issued and stored in Poland.
Electronic invoicing has evolved from simple PDF files sent by email to advanced structured systems that integrate with the national tax infrastructure. Understanding the differences between traditional e-invoices and invoices issued in KSeF is essential for running a business correctly. A business working with an accounting office also has to grant it access — how KSeF permissions for accounting offices work is covered separately.
KSeF has been mandatory since 1 February 2026 for large taxpayers (gross sales in 2024 above PLN 200,000,000) and since 1 April 2026 for other businesses (Article 106ga section 1, Article 145l). Since 1 February 2026, all taxpayers have received structured invoices through KSeF
Basic information about e-invoices and KSeF
Under the VAT Act, an electronic invoice is an invoice in electronic form issued and received in any electronic format (Article 2 point 32), and a structured invoice is an invoice issued using KSeF together with the number assigned to it in that system (Article 2 point 32a). Electronic invoicing has become more popular for environmental reasons and because it allows accounting processes to be automated. E-invoices can easily be integrated with accounting systems and business management software, which significantly increases efficiency and reduces the risk of errors.
The introduction of KSeF means that e-invoicing in KSeF is mandatory for taxpayers (Article 106ga section 1). Paper invoices or traditional electronic invoices can be used only in specific situations – among others for sales to consumers, by taxpayers without a registered office or fixed establishment in Poland, for transactions settled under the non-Union scheme and the import scheme (IOSS), and by taxpayers using the SME exemption under Article 113a (Article 106ga sections 2–3). Until 31 December 2026, transitional exceptions also apply: gross sales of up to PLN 10,000 a month documented with invoices outside KSeF (Article 145m) and invoices from cash registers (Article 145n).
Electronic invoices in any format (for example PDF) can still be issued only in cases excluded from the KSeF obligation (Article 106ga section 2) and during the transitional periods (Articles 145l–145n). In all other cases, the invoice is issued as a structured invoice in KSeF
The dates on which the KSeF obligation took effect were set precisely. Large taxpayers must use the system from 1 February 2026, and other businesses were given two extra months and have been covered by the obligation since 1 April 2026 (Article 145l). Importantly, since February 2026 all taxpayers have received structured invoices through KSeF (Article 106gb section 1), regardless of when they themselves started issuing invoices in the system.
Required details of a KSeF-compliant e-invoice
Under Article 2 point 31 of the VAT Act, an invoice is a document in paper or electronic form containing the data required by the Act and the regulations issued under it. An e-invoice, like a paper invoice, must contain all the details required by law.
The basic details of every e-invoice include a number of key items of information. Every invoice must contain the date of issue and a sequential number assigned within one or more series, which uniquely identifies the document. Full identification details are also required – the first names and surnames or names of the taxpayer and the buyer of the goods or services, together with their addresses.
Every e-invoice must contain the tax identification numbers of the taxpayer and the buyer. For the buyer, the VAT number under which it received the goods or services is required if it differs from the number on the invoice
Detailed information about the transaction is another important part of the invoice. The document must contain the date of making or completing the supply of goods or performing the service, or the date of receiving payment, if it is specified and differs from the date of issue. You must also state the name (type) of the goods or service and the unit of measure and quantity of the goods supplied or the scope of the services performed.
The financial details of the invoice must be stated precisely. The document must contain the unit price of the goods or service excluding tax (net unit price) and the amounts of any discounts, including for early payment, if they are not included in the net unit price. The value of the goods supplied or services performed excluding tax (net sales value) is also required.
The tax details of the invoice include the tax rate, the total net sales value broken down by sales subject to each tax rate and tax-exempt sales, the amount of tax on the total net sales value broken down by the amounts for each tax rate, and the total amount due.
An electronic invoice may be issued and received in any electronic format (Article 2 point 32). A structured invoice must comply with the template provided by the Minister of Finance (Article 106gb section 1) and becomes one only once it has the number identifying it in KSeF, assigned by the system (Article 2 point 32a)
KSeF has specific requirements for invoice numbering. A structured invoice includes, in addition to the invoice data, the number identifying it in the system. This number is assigned to the invoice after it is sent to KSeF, and the invoice is deemed issued on the day it is sent (Article 106na section 1). The invoice can be prepared in another accounting system and then sent to KSeF to be assigned a number – you do not need to use the KSeF application directly.
E-invoice formats – PDF, XML or scan
Paper sales invoices must be issued in at least two copies – one is given to the buyer and the other stays in the seller's accounting records (Article 106gc section 5 of the VAT Act). Under Article 106gc sections 1–3, specific distribution rules apply to e-invoices sent electronically.
The rules for sending e-invoices depend on who issues them. The taxpayer making the sale, or a third party authorised by it, sends the invoices or makes them available to the buyer in the way agreed with the buyer. A buyer issuing invoices on behalf of and for the taxpayer sends them or makes them available to the taxpayer that authorised it to issue invoices, taking into account the rules of the invoice approval procedure of the selling taxpayer.
There is no requirement to use a secure electronic signature when sending e-invoices. A taxpayer issuing e-invoices outside KSeF decides how to ensure the authenticity of origin, integrity of content and legibility of the invoice (Article 106m section 1a), while for structured invoices KSeF ensures this (Article 106m section 1)
An additional situation concerns the entities listed in Article 106c (enforcement authorities and court bailiffs), which send invoices or make them available to the buyer and the debtor while keeping them in their own records (Article 106gc section 3). Since 1 February 2026, the corrective note issued by the buyer no longer exists (Article 106k repealed).
The technical requirements for e-invoices issued outside KSeF (in cases where this is permitted) are relatively flexible. The rules do not impose a specific invoice format on the taxpayer – the choice of format is up to the taxpayer. It may be a PDF e-invoice sent as an email attachment or a fax received in electronic format. Invoices created in Office programs (for example Excel or Word) and in the form of an XML message are also used.
Modern technological solutions are also accepted. An invoice sent as a PDF via mobile apps can be treated as an e-invoice. This position is confirmed by an individual tax ruling (KIS) issued by the Director of National Tax Information on 19 June 2018, ref. 0115-KDIT1-3.4012.227.2018.2.APR (issued before mandatory KSeF – today it is relevant to invoices that may be issued outside KSeF).
In practice, a fuel company implemented a system for sending electronic invoices through a mobile app. By accepting the app's terms, the buyer agrees to receive invoices as a PDF file sent to the email address given at registration. The system automatically generates the invoice and sends it to that address after a purchase at the fuel station.
Although a traditional e-invoice has no specific format, an e-invoice issued in KSeF (a structured invoice) must follow a template consistent with the electronic invoice structure published by the Minister of Finance (Article 106gb section 8). Since 1 February 2026, the FA (3) structure has applied
The differences between traditional e-invoices and KSeF invoices are significant. While traditional e-invoices can be issued in any electronic format, structured invoices in KSeF must follow a specific structure. The current FA (3) structure defines a precise data format that all systems integrating with KSeF must follow.
The buyer's consent to receive e-invoices
Electronic invoices issued outside KSeF are sent or made available to the buyer in the way agreed with the buyer (Article 106gc section 1; until 31 January 2026, Article 106n section 1 required the recipient's acceptance). Under Article 106gc section 4 of the VAT Act, when more than one electronic invoice is sent or made available to the same recipient at the same time, data common to the individual invoices may be given only once, provided that all of this data is available for each invoice.
The Act does not say in what form the arrangement with the recipient must be made. It can therefore be made in writing or electronically. It may also follow from the parties' practice – under the former rules, implied acceptance was recognised, for example when the buyer accepts e-invoices without objection and pays them.
The arrangement with the recipient on how an e-invoice outside KSeF is delivered can take various forms – written, electronic, or following from the parties' practice, for example when the buyer accepts and pays such invoices without objection
The situation is different for KSeF. Until 31 January 2026, when KSeF was voluntary, receiving invoices through the system required the buyer's acceptance. Since 1 February 2026, when KSeF became mandatory, no consent is needed – a structured invoice is received using KSeF (Article 106gb section 1) on the day its number is assigned (Article 106na section 3).
Importantly, for some buyers – among others consumers, foreign entities without a fixed establishment in Poland and entities without a NIP (tax identification number) – an invoice issued in KSeF is made available in the way agreed with them (Article 106gb section 4). In that case the invoice is delivered to the buyer in another way – on paper or electronically, marked with a code giving access to it in KSeF (Article 106gb section 5). Here too, as described above, the form of delivery must be agreed with the recipient.
Rules for storing e-invoices and KSeF
Taxpayers must store all accounting documents, in particular invoices and e-invoices, until the statutory limitation period for the tax liability ends (Article 112 of the VAT Act). As a rule, this period ends after 5 years, counted from the end of the calendar year in which the tax payment deadline passed (Article 70 § 1 of the Tax Ordinance Act (Ordynacja podatkowa)).
The storage obligation is broad and covers various types of documents. You must keep both issued and received invoices, corrective invoices and their duplicates. You must also keep them divided by settlement periods, which makes it easier to organise the documentation and check it.
A business with its registered office in Poland must store invoices in Poland. The exception is invoices in electronic form, which may be stored abroad provided that easy online access is ensured
The requirements for storing e-invoices are set out in detail. The taxpayer must ensure that documents can be found easily and that their authenticity of origin, integrity of content, legibility and availability are maintained from the moment the e-invoices are issued or received until the tax liability expires. These requirements must be met throughout the storage period.
E-invoices can be stored in various ways. Documents can be kept on CDs or hard drives. Backups must be made systematically, and no changes may be made to the documents during storage. The integrity and unchangeability of documents are key to their evidential value.
Special rules apply to storage abroad. A business with its registered office in Poland must store invoices in Poland. There is, however, an exception – the taxpayer may store invoices in electronic form abroad, but must give the tax and customs-tax authorities online access to the invoices by electronic means (Article 112a section 3).
Since 2022, it has been possible to store invoices using KSeF. Structured invoices are stored in KSeF for 10 years, counted from the end of the year in which they were issued
KSeF has brought new storage options. Since 2022, under Article 112aa section 1 of the VAT Act, structured invoices have been stored in KSeF for 10 years, counted from the end of the year in which they were issued – Articles 112 and 112a do not apply to these invoices. After this period, the taxpayer can store structured invoices outside KSeF. A related question is whether changing the invoice issue date in KSeF is possible — we answer it in a separate article.
The practical implications of storage in KSeF are significant. Through KSeF, the tax authority has immediate access to invoices issued via the system for 10 years. The requirement for taxpayers to supply these documents therefore becomes unnecessary. This function allows tax documents to be checked and at the same time relieves taxpayers of day-to-day obligations to provide invoices at the request of the tax authorities.
A business issued sales invoices through KSeF in May 2025. The invoices will be stored in the system for 10 years, that is until the end of 2035. As a rule, the VAT liability for May 2025 becomes time-barred at the end of 2030, and the income tax liability for 2025 – at the end of 2031 (Article 70 § 1 of the Tax Ordinance Act), so in a typical case the KSeF storage period is sufficient and these invoices do not need to be archived outside the system.
If the statutory storage period for invoices in KSeF is insufficient, the taxpayer stores the structured invoices outside KSeF until the limitation period for the tax liability ends (Article 112aa section 2). This flexibility allows businesses to adapt their storage strategy to the specific needs of their activity.
Issuing e-invoices in accounting systems
Issuing e-invoices in modern accounting systems is an intuitive and automated process. To use the integration with KSeF, the business must first enable the relevant function in its accounting system. This usually involves going to the invoicing settings and activating the KSeF integration.
Configuring the system requires a few key steps:
- Going to the invoicing settings section of the accounting system
- Finding the e-invoice and KSeF integration option
- Activating the integration by selecting the relevant option
- Checking the connection with KSeF
- Configuring the parameters for issuing structured invoices
Once the configuration is correct, issuing an invoice becomes a standard procedure. The business goes to the sales section, chooses the option to issue an invoice and fills in all the required data. This includes the contractor's details, the invoice details, a description of the goods or services and the amounts. The system automatically checks that the data is complete and meets the KSeF requirements.
Once you have filled in the invoice data, you simply choose the option to send it to KSeF, and the invoice is automatically sent to KSeF and receives an identification number. This requires the program to be authenticated in KSeF beforehand (for example with a KSeF certificate or a token – tokens can be used until 31 December 2026)
The advantages of automating the process are significant. After the invoice has been successfully sent to KSeF and processed, the system assigns a KSeF number, and the invoice is deemed issued on the day it was sent (Article 106na section 1). In addition, the invoice becomes available in KSeF to the buyer, who can download it and import it into its own accounting system.
Integrating accounting systems with KSeF brings the following benefits:
- Automatic generation of invoices in structured format
- Sending to KSeF directly from the program
- Automatic assignment of KSeF numbers
- Data synchronisation between the accounting system and KSeF
- Easier management of electronic documentation
- Lower risk of errors from manual data entry
Benefits and challenges of e-invoicing
Electronic invoicing brings businesses many benefits that translate into higher operational efficiency and lower costs. Convenience is one of the most important advantages – documents can be issued, sent and archived without printing and physically storing paper documents.
Time savings are another important benefit. Automating accounting processes with e-invoices significantly reduces the time needed to handle documentation. Systems can automatically generate invoices, send them to contractors and update the accounting books without manual data entry. For clients of our accounting firm in Warsaw, we post the invoices downloaded from KSeF.
| Aspect | Traditional e-invoices | E-invoices in KSeF | Paper invoices |
|---|---|---|---|
| Issuing time | Immediate | Immediate + verification | Requires printing |
| Sending costs | Minimal | None | Postal/courier |
| Archiving | Electronic | Automatic in KSeF | Physical space |
| Availability | Online, depending on the archive | Online in KSeF (except during outages) | Physical access |
| Accounting integration | Possible | Full automation | Manual entry |
Automating accounting processes with e-invoices leads to greater efficiency and a lower risk of errors. Systems can automatically check that data is correct and generate the relevant accounting entries
The environmental aspects of e-invoicing are increasingly important for socially aware businesses. Moving away from paper documents helps reduce paper consumption and the environmental footprint of business activity. This is particularly important given growing environmental awareness and sustainability requirements.
The challenges of implementing e-invoicing include the need to adapt IT systems, train staff and ensure an appropriate level of data security. Businesses must also take into account the costs of implementing and maintaining electronic invoicing systems.
Data security is a key challenge. E-invoicing systems must ensure the authenticity of origin of documents, the integrity of their content and protection against unauthorised access. This requires appropriate technical and organisational safeguards.
Preparing for mandatory KSeF
Mandatory KSeF has applied since 2026, but businesses still using the transitional exceptions (Articles 145m and 145n – until 31 December 2026) must prepare to use the system fully. The preparation process should start well in advance to ensure a smooth transition to the new invoicing system.
The key elements of preparation include analysing current invoicing processes, assessing whether the accounting systems used are compatible with KSeF and planning the necessary changes. Businesses should also consider whether staff responsible for invoicing and accounting need training.
The KSeF implementation schedule introduces the obligations in stages:
- 1 February 2026 – obligation for large taxpayers (gross sales in 2024 above PLN 200,000,000)
- 1 February 2026 – receiving structured invoices through KSeF for everyone
- 1 April 2026 – obligation for all other taxpayers
- Until 31 December 2026 – transitional exceptions: invoices outside KSeF for gross sales of up to PLN 10,000 a month (Article 145m) and invoices from cash registers (Article 145n)
- 1 January 2027 – end of the transitional exceptions and financial penalties for issuing invoices outside KSeF (Article 106ni)
All taxpayers have received structured invoices through KSeF since February 2026, regardless of when they themselves started issuing invoices in the system. This means systems must be ready to receive structured invoices
Technical preparation includes checking whether current accounting systems are compatible with the KSeF requirements. If a system does not natively support structured invoices, it may need to be updated or replaced with a KSeF-compatible solution.
The organisational aspects of preparation include drawing up new invoicing procedures, adapting document workflows and training staff. Pay particular attention to emergency procedures and what to do in the event of technical problems with KSeF: an invoice issued in offline mode must be sent to KSeF by the next business day at the latest (Article 106nda section 2), and an invoice issued during an outage announced by the Minister of Finance – within 7 business days of its end (Article 106nf section 4).
