KSeF at a glance – a Practical Guide for Businesses (2026–2027)

The National e-Invoicing System (KSeF) is no longer a “future project” and is becoming a real obligation for businesses. Entry dates, exemptions, contingency modes, corrections, and new reporting rules are causing many misunderstandings around KSeF. Below, we have compiled the most important questions and answers that, in practice, determine whether a company is prepared for KSeF in 2026–2027.

 

TABLE OF CONTENTS

1. From when is KSeF mandatory?
2. Do I have to receive invoices in KSeF before I start issuing them?
3. Does the PLN 10,000 limit mean there is no KSeF obligation?
4. Is KSeF 2.0 a production environment?
5. Is a certificate alone sufficient to use KSeF?
6. What is the Certificates and Authorisations Module (MCU)?
7. Are invoices in KSeF always issued online?
8. What is the issue date and receipt date of an invoice in KSeF?
9. Will there be corrective notes in KSeF?
10. What types of corrections does KSeF provide for?
11. How should a correction be technically presented in KSeF?
12. When should a “downward” correction be recognised for VAT purposes?
13. How does KSeF affect JPK_VAT?
14. Is private rental subject to KSeF?
15. When must a foreign company apply KSeF?

 

From when is KSeF mandatory?

The obligation to use the National e-Invoicing System (KSeF) will be implemented in stages:

• from 1 February 2026 – taxpayers whose sales (including VAT) in 2024 exceeded PLN 200 million,
• from 1 April 2026 – other active VAT taxpayers,
• from 1 January 2027 – taxpayers covered by a transitional exclusion (PLN 10,000 monthly limit).

These are statutory dates, not announcements by the Ministry of Finance. As of today, there is no draft legislation providing for another postponement of the KSeF obligation.

 

Do I have to receive invoices in KSeF before I start issuing them?

Yes. From 1 February 2026, all VAT taxpayers are obliged to receive invoices via KSeF, regardless of when they start issuing them.

This also applies to taxpayers who:

• start issuing invoices in KSeF only from 1 April 2026,
• use transitional exclusions.

An invoice issued in KSeF is deemed delivered at the moment the KSeF number is assigned, even if the taxpayer does not log into the system or download the document. KSeF does not send notifications about new invoices.

 

Does the PLN 10,000 limit mean there is no KSeF obligation?

Until 31 December 2026, a taxpayer may issue invoices outside KSeF if the monthly value of invoiced sales does not exceed PLN 10,000 gross.

Once the limit is exceeded, the obligation to issue invoices in KSeF arises starting from the invoice by which the limit was exceeded.

The exclusion applies only to issuing invoices. The obligation to receive invoices in KSeF remains unchanged.

 

Is KSeF 2.0 a production environment?

No. The KSeF 2.0 environments made available from autumn 2025 (the pre-production environment and the demo version of the Taxpayer Application) are intended solely for testing purposes.

Invoices issued in these environments have no legal effect, and data entered into the test system are not transferred to production and may be deleted.

 

Is a certificate alone sufficient to use KSeF?

No. A certificate in KSeF only confirms the identity of the user.

In order to issue or receive invoices, appropriate authorisations to act on behalf of the taxpayer must be granted. Lack of authorisations is one of the most common causes of problems with access to KSeF.

 

What is the Certificates and Authorisations Module (MCU)?

The MCU is a central KSeF module through which, from 1 November 2025, the following activities are performed:

• certificate management,
• granting and revoking authorisations.

Without a properly configured MCU, it is not possible to issue or receive invoices in KSeF 2.0.

 

Are invoices in KSeF always issued online?

No. KSeF provides for various invoice issuance modes, including:

• online mode,
• offline modes (including offline24),
• contingency modes.

Each mode is subject to different rules and deadlines for submitting invoices to the system.

 

What is the issue date and receipt date of an invoice in KSeF?

In KSeF:

• an invoice issued online has an issue date equal to the date it is sent to the system,
• in offline24 mode, the decisive date is the date indicated in field P_1,
• as a rule, the receipt date of an invoice is the moment the KSeF number is assigned.

This has a direct impact on the moment of VAT settlement.

 

Will there be corrective notes in KSeF?

No. With the entry into force of KSeF, Article 106k of the VAT Act is repealed.

This means that the purchaser will not be able to correct formal errors. Any correction, including minor data, will require the seller to issue a correcting invoice.

 

What types of corrections does KSeF provide for?

In the KSeF logical structure, the field RodzajFaktury (InvoiceType) may take, among others, the following values:

• KOR,
• KOR_ZAL,
• KOR_ROZ.

Additionally, it is mandatory to indicate the field PrzyczynaKorekty (ReasonForCorrection).

 

How should a correction be technically presented in KSeF?

KSeF allows several methods of presenting a correction, including:

• a “difference-based” correction,
• a correction using the StanPrzed (StateBefore) marker,
• a correction using the storno method.

The choice of method affects the way documents are automatically posted in accounting systems.

 

When should a “downward” correction be recognised for VAT purposes?

If a correcting invoice reducing the taxable base is issued in KSeF, the VAT reduction is recognised in the period in which the correction is issued.

Confirmation of receipt of the correcting invoice by the purchaser is not required.

 

How does KSeF affect JPK_VAT?

After KSeF enters into force, the KSeF number of the invoice is reported in JPK_VAT.

If the number has not been assigned, the markings OFF, BFK, or DI are used. Once the KSeF number is assigned, it may be necessary to correct JPK_VAT. Failure to make a correction may result in penalties.

 

Is private rental subject to KSeF?

Private rental does not always constitute business activity, but it is often associated with VAT taxpayer status.

If the tenant is an entrepreneur and requests an invoice, that document is subject to the KSeF obligation. If no invoice is issued to a private individual, KSeF does not apply.

 

When must a foreign company apply KSeF?

A foreign company is subject to the KSeF obligation only if it has a fixed establishment in Poland (FE) and that FE takes an active part in the specific sales transaction.

The mere presence of employees or infrastructure in Poland does not determine the KSeF obligation. Auxiliary activities such as IT, HR, or back office functions do not automatically trigger the obligation to issue invoices in KSeF. The decisive factor is the actual involvement of the fixed establishment in the sale.

 

Author:
Piotr Steczyszyn, Senior Manager, MDDP Outsourcing