KSeF, or National e-Invoice System, is a nationwide ICT system prepared by the Ministry of Finance, which organizes the issuance and circulation of sales documents in one place. In practice, this works so that instead of sending a PDF by email, the company issues an e-invoice as data, that is, a structured invoice, and then transmits it to a central platform. Such an electronic invoicing platform accepts the document, checks compliance with the logical structure, and after positive verification assigns an identifier, that is, the KSeF number. It is this number, often called the invoice KSeF number, which confirms that the document has been accepted for circulation in the system.
In the context of KSeF, it is important to distinguish between concepts. For the user, the issue of the invoice, the correct issuance and the moment of issue are important, but in the background the system considers the document as a record in the KSeF system with specific processing statuses. Therefore, in conversations about how KSeF works, topics such as sending an invoice to KSeF, the ability to receive invoices, storage rules and access to invoices in KSeF arise. All this adds up to real invoicing in a new model, in which for transactions covered by KSeF, the document functions in circulation as an e-invoice in a central system and not in multiple distributed channels.
The reason the topic is hot is due dates and thresholds. The introduction of the National E-Invoice System is phased, and the word “mandatory” ceases to be a theory. The obligation to issue invoices in KSeF has occurred and will occur:
— from 1 February 2026 for taxpayers whose value of sales including VAT exceeded PLN 200 million in 2024
— from 1 April 2026 for other taxpayers, except those whose monthly sales value documented by invoices does not exceed PLN 10,000 gross. Such taxpayers are not obliged to issue invoices in KSeF until the end of 2026, and the obligation will cover them from January 1, 2027.
At the same time, there is the issue of access and security. To use KSeF, you need a login and proper authentication. Depending on the scenario, solutions such as the Trusted Profile, the qualified signature, as well as corporate solutions such as the electronic seal, come into play. In practice, you will also come across the concepts of certificate and KSeF certificate, they are used for secure access and integration, including through the KSeF API. The permissions layer is also crucial, i.e. the rules of authority to use KSeF, manage permissions and act according to the permissions granted in the organization. This is relevant both when the decision-maker in the company operates, and when access is given to the finance department or a collaborating accountant.
The emergency scenario is also important. The system provides procedures in case of unavailability of KSeF, which is why the concepts of offline mode and offline mode24 function. The offline mode refers to the situation when the inaccessibility concerns the KSeF system itself, and the offline mode24 supports cases where the problem is due, for example, to the quality of the connection or the lack of internet on the part of the taxpayer, which makes it difficult to issue and send e-invoices to the KSeF. This is not a technical detail, but an answer to the question of what to do when you need to issue a document, and it cannot be immediately successfully sent to a central platform.
In this article, I explain how the central billing model works. I will show how the issuance and circulation of electronic invoices in KSeF looks like, when and for whom it applies, and when it does not apply, for example in selected cases of sales to a natural person who does not conduct business activities. We will also discuss how to approach the topic when the document was issued outside the KSeF, and then it needs to be settled in the realities of the mandatory system. We will also discuss the differences when the password KSeF and PEF appear, because these systems tend to be confused, even though they serve different purposes.
What is the national e-invoicing system as an electronic invoicing platform
How ksef works in practice, national data flow and validation
KSeF is the central platform of the Ministry of Finance, which acts as a “gateway” for invoicing. She is not interested in the appearance of the document. What matters is the data and their compliance with the logical structure. Therefore, in practice, the National e-Invoice System is more of a data processing system than a place to view PDFs.
The simplest way to put it this way:
— the issuer prepares the e-invoice as data
— the system accepts the document in a format that complies with the requirements, i.e. as a structured invoice
— validation occurs, that is, checking that the fields are correctly arranged and complete
— after a positive pass, the system assigns an identifier, i.e. the KSeF number
— from that moment the document functions in circulation as an e-invoice in the KSeF system
If validation fails, the document does not enter circulation. Then there is no “almost accepted invoice”. There is a rejection and the need to improve the data before it can be sent as an invoice to KSeF again.
What goes into the KSeF system
In KSeF, an invoice is not a “printable file”. It is a set of transaction information stored in a specific structure. Therefore, the concepts invoice, e-invoice and structured invoice are not interchangeable here.
In practice, KSeF receives data that you normally see on an invoice, only saved in a form that the system understands:
— details of the parties to the transaction, i.e. identification of the entity and the counterparty
— sales items, rates and VAT amounts
— dates related to issue, sale and payment
— additional information required by the regulations and structure of the document
This is why the term “invoice in KSeF” is often encountered. It is about invoices that already exist in central circulation. If the invoice was issued outside the KSeF, and there is already an obligation to issue invoices in KSeF, then this usually requires an orderly process. The PDF itself does not automatically become an e-invoice.
The role of the issuer of invoices in circulation
At KSeF, what matters is who acts and in what role. Concepts such as taxpayer, entity, entrepreneur and issuer of invoices appear in the system, because the central circulation enforces clear rules of responsibility.
In practice, this means two things.
First, access to KSeF is not “for everyone who has a login”. In order to really use KSeF, you need to have the right permissions. Topics such as KSeF entitlement rules, permissions management, and acting in accordance with the permissions granted are included here.
Secondly, the way to enter the system is important, that is, login and authentication. Depending on the situation, a trusted profile, a qualified signature, sometimes also solutions based on a certificate or KSeF certificate are used, and in organizations often there is also an electronic seal. Thanks to this, the system knows who actually performed the action, for example who initiated the issuance of the invoice and who is responsible for sending it within the KSeF.
When will it go into effect in 2026 and what does it mean
What changes February 1, 2026 in the schedule
Mandatory KSeF does not start one day for everyone. The schedule is phased, and the first key date is February 1, 2026. From then on, the obligation covers taxpayers whose value of sales, including VAT, exceeded PLN 200 million in 2024. In practice, this means that invoicing begins to work in a model where the central platform accepts the document as data, not as a PDF file.
From this date, part of the market works like this:
— it is necessary to issue invoices in the form of a structured invoice within the framework of the KSeF
— sending an invoice to KSeF becomes the standard of the sales process
— each e-invoice receives an identifier, i.e. KSeF number
— invoices go into common circulation as invoices in KSeF
Ksef applies to selected cases, and when ksef does not apply
The next step is April 1, 2026. From that date, the obligation covers the remaining taxpayers, but with an important transitional exception. If the value of sales documented by invoices on a monthly basis does not exceed PLN 10,000 gross, then until the end of 2026 there is no obligation to issue invoices in KSeF.
There are also situations in the legislation in which KSEF applies or KSEF does not relate to a specific transaction. Most often, confusion comes from mixing B2B invoices with consumer invoices.
It is worth remembering two orders:
— in the trade between companies, KSeF is the standard for invoices covered by the obligation
— invoices for a natural person not conducting business activities are voluntary in KSeF. They can be issued in the system, but you do not have to
Implementation of ksef, what the transition to the new standard looks like
The implementation of KSeF does not involve changing the invoice template. The model of operation of the process is changing, because the national e-invoicing system is based on data, validation and entitlements. This is especially important if the company has more than one person who can issue documents.
In practice, implementations usually include three areas:
— access and security: login, authentication, sometimes trusted profile, qualified signature, company seal, as well as KSeF certificate or certificate
— permissions: who has the right to issue a document, who has the rights to use KSeF, and how to manage permissions in the organization
— tool: some companies work in the application of the Ministry of Finance, some use an external solution as a provider. Then comes the topic of the KSeF API and how the system is supposed to receive and send documents within KSeF
How to invoice and send invoices to ksef
Postshipment statuses and document identification
In the KSeF model, the most important thing is that issuing an invoice is not just a click on “save”. The document must be correctly sent and received by the ICT system. Only then can you be sure that the structured invoice functions as an e-invoice within the KSeF.
The process looks simple, but it has its own “checkpoints”:
— prepare sales data, including items, VAT rates, amounts and the total value of sales
— the system generates the document as a structured invoice, i.e. data consistent with the structure
— an invoice is sent to KSeF, i.e. the document is transferred to the central platform
— KSeF verifies the data, and when everything is correct, gives an identifier, that is, the number of KSeF
— from that moment the invoice is in circulation as an invoice in KSeF and can then be safely received on the buyer's side
In everyday work, you will also come across the concept of invoice KSeF number. This is an identifier that allows you to clearly indicate the document in the system, regardless of what tool you are viewing it in. This is important when there are a lot of invoices and you want to quickly find a specific item among KSEf invoices.
How to use ksefs and manage permissions
In order to use KSeF at all, you need to have the right range of permissions to use KSeF. This is crucial especially when several people in the company are supposed to issue documents and others only receive and post them.
In practice, entitlements include three typical situations:
— someone has the right to issue invoices and send them to KSeF as an issuer
— someone has the right only to receive documents, i.e. view and download invoices from the system
— someone manages access, that is, they can assign roles and work on permissions in the organization
Here it is important to distinguish who is the “owner” of access in the system. KSeF operates at the entity level, so it matters whether the activities are carried out by the taxpayer, a specific entity or a person acting on his behalf, for example, an accountant or a finance employee. Thanks to this, it is known who is responsible for issuing, sending and receiving documents in the tax circulation.
In the background, there is also the question of the signature. Depending on the scenario, tools and roles in the organization, concepts such as signature, qualified signature, trusted profile solution, and in companies also electronic seal appear. If the deployment is based on certificates, the certificate and the KSeF certificate appear as an element that organizes access and security.
KSeF entry methods
KSeF is a central platform, so the entrance to it must be unambiguous. That is why login and authentication are important. Depending on how you work and what roles you have, you can use different methods.
Most often you will encounter three paths:
— entry through the KSeF Taxpayer's application as a user who wants to issue or receive documents
— entry through the KSeF 2.0 Taxpayer application, when you need functions adapted to changes in KSeF 2.0 and support for new rules
— input from an external tool, where integration works and communication goes through the KSeF API, often referred to as the KSeF API
If you use an external tool, it is important how the provider works. A good supplier not only allows you to issue invoices, but also handles sending and receiving correctly, maintains data consistency and is able to operate stably, even when technical problems or periodic unavailability of KSeF arise.
Security and access in KSeF
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Who approves and who acts on behalf of the company
At KSeF, security starts with a simple question: who is authorized to operate in the system at all. The national e-invoicing system differentiates roles and assigns activities to a specific entity. Thanks to this, it is known whether the act was carried out by the taxpayer, the entity in question or the person acting on his behalf.
In practice, three areas of responsibility are most often allocated in the organization:
— the person or team that actually has to issue the documents and is responsible for issuing the invoice
— the person who is to receive documents and supervises the circulation of electronic invoices on the purchasing side
— the person who manages access, that is, manages permissions and decides who can use the system
This is important, because with the obligation to issue invoices in KSeF, it is not enough that “someone has an account”. You need to have consistent rules about who approves actions, who executes them and who is responsible if there is an error in the data or in the shipping process.
Comparison of approaches and consequences for the process
To use KSeF, you need login and authentication, because it is a government platform, and actions must be assigned to a specific person and entity. The Ministry of Finance provides for several methods of confirming identity and granting access, depending on the scenario.
Most often you will encounter:
— Trusted profile when access is implemented as a user in a simpler model
— solutions based on a qualified signature, where a high level of reliability and formal proof of identity is required
— a corporate approach with the use of an electronic seal, when activities are to be linked to the organization and not just to one person
— a model based on the certificate and the KSeF certificate, when stable, repeatable authentication is key in integrations, for example when communicating via API
It is worth distinguishing between concepts that sound similar but do different things. The Trusted profile and the qualified signature are used to confirm the identity of the user, and the KSeF certificate is a tool used mainly in the context of integration and automatic communication with the system. This affects the process, because the choice of authentication method can determine how efficiently you can issue, send and receive e-invoices in everyday work.
The most common scenarios for transmitting and receiving access
In KSeF, nothing happens “automatically”. Even if you have access to the platform, specific activities need to be given the right scope. That is why the topic of permissions to use the KSeF and the management of permissions so often arises.
In practice, the most common scenarios look like this:
— granting authority to the person who is to issue invoices and carry out the issuance on behalf of the company
— granting rights to a person who only has to receive documents, i.e. to receive invoices and have an overview of invoices in KSeF
— Give permissions to the manager, who can assign roles and update access when responsibilities change in the team
— revoke privileges when cooperation ends or the scope of tasks changes
This approach makes sense especially if the company works through the KSeF taxpayer application or through an external provider tool, where part of the operation goes through the API. Independently of whether the entrepreneur acts alone or uses the help of an accountant, the principle is one: the powers must match the role, because only then is KSeF safe and predictable.
Operation in case of unavailability of xsefs
Differences in standards and integrations
Before we get into emergency situations, it is worth disenchanting the abbreviation that often appears in the questions: KSeF and PEF. This is not the same, even though both topics revolve around electronic invoicing.
— KSeF is a national system for electronic invoices in business transactions. Het actie als een centrale platform van de Ministerie van Financiën en toepassingen voor tax-settlementen, waaronder VAT
— PEF is an Electronic Invoicing Platform used mainly for the exchange of documents in public procurement, it works in a different logic and in different standards than KSeF
In practice, integrations and data flows look different. A tool or software vendor can support one, the other, or both, but these are separate processes and separate paths of circulation
Therefore, in the context of KSEF's obligation, it is crucial whether your tool can issue a structured invoice, send it correctly to KSEF and enable it to be received later in central circulation.
What does offline24 mean in practice
KSeF is a nationwide ICT system, so it is worth assuming that sometimes there will be problems on the Internet, integration or simply on the user side. Quindi i concepti di modalità offline e modalità offline24 comprese in questi due modalità facile da confusare e la differenza è importante.
Modo offline a. A modalità offline 24 può essere usato quando il KSEF è in eseguire, ma ci sono disturbi sulla parte del utente, come scarcity di internet o poor-qualità di connessione, che fa un problema e inviare un fatto.
O principal que deve ser: a modo offline24 não significa “Eu fazer uma conta como antes e a ser.” Het is een control-mechanisme in die uw document uitzending van de KSeF, men je de obligatie om het te ontvangen naar het systeem in een korte tijd. In practice, this means:
— you issue an invoice outside the KSeF, because you cannot send it effectively at a given moment
—, i.e., a data form consistent with the structure
— vous envier l'invoice à KSeF, à l'ultima en la dernière jour de travail après la jour de l'issue
This is not a “fallback option for the elect”. Het is een oplossingen dat in het proces is waarom de bedrijfsproblemen van een grote werkt of werkt in de veld, waaronder de internetverbinding kunt instabiliteit.
What Happens When You Go Back Online
When the problem passes and you can send documents normally again, you return to the standard circulation. El clave es qué se a un documento estada del sistema.
— a document is sent to KSeF by sending an invoice to KSeF
— the system performs data validation according to a logical structure
— if everything is correct, the document gets an identifier, that is, the KSeF number and becomes part of the invoices in the KSeF
— a partir del momento que el contractor puede obtener los invoices en su acceso a la sistema KSeF, y tiene la coherencia de la ciclista de la baca
Here you can see the practical difference between a “document issued outside the system” and an e-invoice in KSeF. An invoice issued offline or offline24 is a transitional stage. Sólo a partir de la sistema y assegnando el número de KSeF, es funciona como un invoicura elettronico en circulação centrale.
What changes in structures, validation and communication
What goes into XML after updating
KSeF 2.0 is in practice de même objektiv, mais refinement des principles de l'exploitation technique et des processus. A,. This is important because KSeF does not evaluate the appearance of the document. The system evaluates the correctness of the data.
In praxis, a.
— details of the parties to the transaction, i.e. identification of the issuer and the buyer
— sales items and amounts, including VAT and total value of sales
— the dates and information required for the correct issuance of the document in the tax circulation
—
If a company has an obligation to issue invoices in KSeF, then one thing is crucial from the process side. The data must be correctly mapped to the required structure. Otherwise, the system will reject the document before it becomes a full-fledged e-invoice in circulation.
How is communication with the system and confirmations
KSeF can be operated in different ways. Some work through applications made available by the Ministry of Finance, others focus on integrations. A KSeF API, a,. In practice, in the integration descriptions you will also come across the term KSeF API.
What does this change in daily invoicing?
— the company's system can automatically create a document as a structured invoice and allows you to issue without manually rewriting the data
— it becomes possible to send documents as invoices in bulk to KSeF and receive feedback on their statuses
— you can also automatically receive invoices and build a consistent document flow on the purchasing side
This is where the quality of the solution that the supplier implements matters. Ha és a responsable de que la integrazione funciona estable, que se funciona correctamente, se puede resumir la comunicación después de problemas, y que no se las statuses de los invoices en el sistema.
What do feedback messages mean
In KSeF, it is important to distinguish between the fact that the document has been prepared and that it has been successfully accepted by the platform. For a company, a moment when KSeF issues an identifier is crucial. A kSef a.
The most common messages that the exhibitor encounters:
— document adopted. XeF number assigned. The invoice exists in the XeF system
The document was rejected. You need to correct the data because the validation of the structure does not match
— un problema tecnico, como no disponibilidade do KSeF, que influentes a se puede enviar un entrada immediatamente
In practice, statuses decide what to do next:
— a document is accepted, a counterparty can then receive it normally, and the company has a consistency of sales and settlements
— if the document is rejected, there is no “partially invoked”. There is a need to improve the data and resend
— si une scenario d'urgence entre, il modalità offline ou il modalità offline24, et dopo restituire online, il documento deve essere inviato a XeF per ricevitare il numero XeF
In the background, the security layer works all the time. A, a, a. They determine who actually performs the activity in the system and whether the company operates in accordance with the granted privileges and the scope of the rights to use the KSeF.
Resumen
KSeF is not a cosmetic invoking, but a change in the logic of circulation. What matters is the data, the correctness of the structure and whether the document was successfully accepted by the system, and not what the printout looks like. A partir de la parte de trabajo quotidiana, tres deveros cruciais: enviando e enviar os contos a KSeF, a contender a KSeF e acceso, ie. logging, verificação e rêveberiya mafên.
In the background, there is also a scenario for difficult moments: offline mode and offline 24 mode in case of system unavailability or problems on the user side. This is important because if a sale is to be covered by KSeF, an invoice issued outside the system is usually a transitional stage. Por fin, az a KSeF és a a KSeF, a.
If you want to go through it without chaos in the documents, you can organize the flow of invoices and work on documents in Altera.app. L'applicazione supporta, tra altri, distribuzione elettronica di fatti con acceptances, OCR intelligente per lettura di fatti, monitoraggio dei fatti e punti di pagamento, commentare i documenti e preparazione dei pacchetti di trasferimento a banque. As a result, invoices are under control and the process is put in order before the pressure of KSeF arises.
