KSeF - how to prepare for mandatory e-invoicing?

The National e-Invoice System (KSeF) will be introduced in a phased manner according to the following timetable: commencing February 1, 2026, for large entities whose turnover exceeded PLN 200 million in 2024, and from April 1, 2026, for all other entrepreneurs. For the smallest taxpayers whose gross monthly sales do not exceed PLN 10,000, the mandatory use of KSeF will be deferred until January 1, 2027.

The introduction of the obligation to use structured invoices is a big change that will not only affect the format and transmission of invoices in business-to-business relations but will also force VAT taxpayers to reengineer their existing business processes, from sales and purchasing processes to accounting and tax procedures in place in companies. Thus, it is worth starting the implementation of the KSeF system now, as our experience shows that the transition to structured invoices can involve even several months of implementation (the larger the company / more complex the invoicing model, the longer and more difficult the process will be).

Please find below:

• main principles of the KSeF system,
• our recommendations on how to prepare for mandatory e-invoicing,
• the range of services we offer for the implementation of the KSeF system.

We encourage you to plan the KSEF implementation in advance

Should you need support in the KSeF implementation process, the Forvis Mazars Tax Department remains at your disposal (Kinga Baran, Partner - k.baran@forvismazars.com).

If you decide to use our services during implementation of KSeF, we would like to emphasize that requesting support should be as soon as possible, due to the relatively short time remaining before the mandatory e-invoicing system goes into effect, the upcoming holiday season, and the number of entities that may be looking for help in implementing KSeF at the same time.

The range of services offered by Forvis Mazars Tax Advisory Department is described at the end of this message.

Main principles of the KSEF system

1. What is KSeF?

• KseF is a government platform that enables users to issue and share so-called structured invoices ("e-invoices") in real time.

2. What is a “structured invoice” (“e-invoice”)?

• A structured invoice is an electronic invoice in xml format, issued using KSeF and having a unique number assigned by KSeF. Its data scope must comply with the e-invoice logical structure (xds schema), as announced by the Ministry of Finance.

• The-invoice schema is composed of several hundreds of fields, from which you must select the data to be completed for each type of invoice. Schema fields are divided into 3 categories:
  - mandatory fields - fields that must be filled in each time; they correspond, as a rule, to the mandatory elements of an invoice specified in the VAT Act;
  - optional fields - completion of these fields is not always mandatory, they are required only in certain situations (e.g. "buyer's address" is an optional field for the so-called "simplified invoices", i.e. invoices containing a total amount due not higher than PLN 450, while it is mandatory for invoices other than "simplified"),
  - optional data - this is information that is not required by VAT regulations, but some of this type of data is currently shown on invoices by VAT taxpayers to facilitate settlement of transactions (e.g. CN codes, Polish Classification of Products and Services PKWiU, transport information, information on bank account number or date of payment).
• A structured invoice is not a PDF invoice or a scan of a paper invoice - such invoices will not be able to be processed on the KSeF platform.

3. Which entities will be obliged to issue e-invoices starting from 1 February 2026?

• The obligation of issuing e-invoices will, as a rule, apply to:
  - active VAT taxpayers with a registered seat in Poland and
  - foreign entities registered as Polish active VAT taxpayers that have a fixed establishment in Poland - if you are not sure whether you have a fixed establishment in Poland, we recommend you to analyze the VAT status of your business as soon as possible.

The above applies to entities that achieved turnover exceeding PLN 200 million in 2024.

From April 1, 2026, the obligation will be implemented for other entrepreneurs, with the exception of the smallest “digitally excluded” taxpayers whose transactions involve small amounts (up to a total sales value of PLN 10,000 per month) and who will be subject to this obligation from January 1, 2027.

4. What transactions will be subject to documentation by e-invoices starting from 1 February 2026?

• E-invoices will be mandatory for activities subject to VAT in Poland, i.e. domestic supplies of goods and services between businesses (B2B) and to public authorities (B2G).
• Outside of KSeF, invoicing of consumer sales (B2C transactions) and invoicing of transactions covered by special procedures (e.g., in the non-EU procedure for certain services and the special procedure for distance sales of imported goods) will take place. However, based on the draft amendment to the VAT Act, there is an optional possibility to issue structured invoices also to natural persons who do not conduct business activity.

5. What sanctions for not issuing structured invoices?

• In case of failure to comply with e-invoicing regulations, the tax authority will ultimately be entitled to impose a penalty of:
  - up to 100 percent of the amount of VAT shown on the invoice or
  - up to 18.7 percent of the amount of total receivables shown on the invoice (if there is no VAT amount on the invoice).

The above sanctions are to come into force only on January 1, 2027, which results from the need to provide taxpayers with sufficient time to adapt to the new regulations and avoid immediate negative consequences in the initial period of KSeF implementation.

6. What is the current state of regulations relating to mandatory e-invoicing using the KSeF platform?

• On June 17, the Council of Ministers adopted a draft amendment to the Act on Goods and Services Tax and certain other acts concerning the National e-Invoice System (KSeF). The draft confirms all key proposals regarding the issuance of e-invoices that were submitted by entrepreneurs during consultations. For e-invoicing to become mandatory for B2B transactions, the current VAT regulations must be appropriately amended. The legislative process is expected to be completed by the vacations.
• On June 30, 2025, the Ministry of Finance published the technical documentation of the KSeF 2.0 API and the final version of the logical structure of the e-Invoice FA(3). The KSeF 2.0 API is a set of specifications enabling the integration of financial and accounting systems with the National e-Invoice System. The KSeF 2.0 introduces, inter alia, an offline24 mode enabling the issuance of structured invoices without direct internet access, as well as the capability to attach appendices to invoices.
• On September 30, 2025, the KSeF 2.0 API will be made available for open testing to all integrators and enterprises. The currently available materials already allow for planning the integration architecture, preparing changes, and developing prototypes.
• In November 2025, a test version of the KSeF 2.0 Taxpayer Application, implementing the full range of functions available through the KSeF 2.0 API, is scheduled to be released.
• On February 1, 2026, the production version of the system will be launched, enabling the issuance of structured invoices in commercial transactions.

Preparation for KSEF - our recommendations

Below you will find our list of recommended actions to take to prepare for mandatory e-invoicing:

1. Appointment of the person(s) responsible for the implementation of KSeF in the company

• Having determined that you will be required to issue e-invoices on the government's KSeF platform after 1 February 2026 (1 April 2026), we recommend forming a working group to participate in the KSeF implementation process. It would be great to involve in the KSeF implementation process the representatives of the various departments in the company that deal with invoices and are responsible for, among other things:
  - sales invoicing,
  - receiving and accounting for purchase invoices,
  - accounting / tax settlements,
  - implementing / maintaining IT systems,
  - customer service / working with suppliers.

2. Obtaining authorization to operate KSeF

• In order to issue/access e-invoices, it will be necessary to obtain authorizations (the taxpayer must authorize a dedicated person to operate the KSeF platform, who will obtain authorizations to issue e-invoices and receive them).
• The granting of authorizations is done electronically (interface software, ksef.mf.gov.pl) or on paper (ZAW_FA form).

3. INVOICE CONTENT - determination of the type of invoices issued / determination of available and missing data

• In order to optimally prepare for e-invoicing, it is necessary to review the current invoicing process. The purpose of such a review should be to determine:
  - what types of transactions / transactions to what clients are subject to invoicing,
  - how the invoicing process currently works, i.e. where the data is obtained from, what data is on the invoices, what invoicing provisions are in contracts, who in the company is responsible for issuing invoices, whether attachments are used, etc.,
  - what data, in the context of compliance with the schema (i.e., the scope of data in accordance with the logical structure of the e-invoice published by the Ministry of Finance), should be included on invoices, and what data the entrepreneur wants to include additionally on a voluntary basis (alternatively, what data will be provided to contractors outside KSeF).

4. SALES INVOICES WORKFLOW - analysis of the impact of KSeF on the e-invoicing process

• There is a number of aspects that need to be taken into account when implementing the KSeF (e.g., archiving the KSeF number, the need to provide a separate workflow of attachments, double circulation of foreign invoices, inclusion of optional data on e-invoices or outside the KSeF, etc.). Therefore, part of the KSeF implementation should also be an assessment of the impact of the new regulations on the invoicing process in the company and planning the appropriate / optimal modification of this process to the extent compatible with the new regulations.

5.     PURCHASE INVOICES WORKFLOW - planning the process

• The KSeF government system will not send a notification that a business has received purchase invoices from its vendor/service provider, which means that the taxpayer will not automatically know at all that an invoice has been issued to it and posted on the KSeF platform. In this regard, the solution may be to take advantage of the offerings of IT system providers, which generally offer the ability for the buyer to automatically download e-invoices from KSeF.
• It should also be underlined that according to the draft amendments to the VAT Act, the KSeF number assigned to e-invoices is to be required in transfer titles - hence it is necessary to ensure that this number is collected and properly archived for purchase invoices (and not just sales invoices).
• It is advisable that part of the implementation process should also include planning the workflow/verification of received purchase invoices (workflow).
• Consideration should also be given to making appropriate amendments to agreements with contractors - so as to clarify in them the method of delivering invoices and protect against the deduction of VAT from so-called "empty invoices," for which there are already disproportionately high monetary sanctions.

6. IT tool selection

• In order to ensure communication with the KSeF government platform it is necessary to have adequate technological facilities - in this regard, we recommend that you obtain Polish IT support, as foreign IT solutions for KSeF may not be able to cope with the numerous and dynamic changes related to e-invoicing in Poland.
• As a first step, we suggest that you verify with your ERP system provider whether it offers an IT tool to communicate with the KSeF platform. You should consider with the IT supplier what ERP system integrations may be necessary and plan them well in advance (so that there is still time to test new solutions).

7. Adjustment of internal regulations /policies and contracts

• Due to the implementation of KSeF in the company, contracts, regulations, as well as potentially other types of internal and commercial documents, may need to be modified. Please do not forget to review them in the context of the new legislation and update them where necessary.

Our support in KSEF implementation

In order to prepare for mandatory e-invoicing, we offer you the following types of tax services, which can, depending on your needs, be carried out in a combined manner or as individual services.

E-invoice implementation services

1. Invoicing process mapping

• The mapping would include an analysis of the company's current sales invoicing process based on a sample of invoices and contracts that form the basis for the invoicing process.
• The purpose of the service would be to adapt the currently issued invoices to the xds schema - i.e. to determine the content of the e-invoices, in line with the format required for their issuance by the KSeF government platform (to determine the elements of the e-invoice based on the schema announced by the Ministry of Finance) and to provide possible recommendations for changing the content of the contracts.
• The work would result in a map of the invoicing process including, in particular:
  - identifying the types of sales invoices issued,
  - determination of the scope of data present on currently issued sales invoices / advance invoices and corrective invoices that will need to be sent to KSeF after 1 February / 1 April  2026, indicating which data is treated as mandatory and which as optional according to the schema, (e-invoice logical structure announced by the Ministry of Finance) - adaptation of invoice content to the schema,
  - identifying missing mandatory data on sales invoices (if such gaps are identified),
  - making recommendations on amending the content of contracts in light of the planned changes concerning e-invoicing,
  - in case of a decision not to include optional data in the KSeF - the mapping process may also include consultations on the identification of an alternative way of sending optional data outside the KSeF.
• The above map will be able to be used by the IT department / IT supplier in the KSeF implementation process, as well as provide a starting point for the adoption of internal invoicing rules, in line with the new VAT regulations.

2. PROCESS PLANNING - assessment of the impact of the KSeF regulation on sales and purchasing processes

• The purpose of our analysis would be to gain insight into the current sales and purchasing processes of the company in the context of the planned VAT amendment on e-invoicing.
• The work would result in a report indicating:
  - the impact of the KSeF regulation on the company’s sales and purchasing processes,
  - identification of persons responsible for the invoicing / invoice approval process in the company,
  - identify areas of potential risk / issues that need to be addressed ("red flags") during the e-invoicing implementation process,
  - making recommendations for changing the invoicing process,
  - identifying potential opportunities created by KSeF.

3. Amendments to contracts / commercial documents

• In connection with the entry into force of the obligation to issue e-invoices in relations with entrepreneurs, we are ready to support you in the analysis of commercial documents (contracts, general terms and conditions, rules and regulations) in terms of the new VAT regulations and to present a proposal for changes so as to ensure compliance of these documents with the proposed VAT regulations.

NOTE: It is recommended that this service be based on either a previously performed invoice mapping service or a VAT audit.

4. Assistance in preparation of the internal invoicing procedure

• Upon your request, we can prepare an internal invoicing procedure that formalizes the rules for the issuing of sales invoices / workflow of purchase invoices in the context of the new e-invoicing rules.
• The preparation of the invoicing procedure would be based on an interview with company representatives and would aim to align the invoicing process / purchase invoice workflow with the KSeF regulations.
• Such procedure could include:
  - identification of persons responsible for issuing invoices (including those authorised to operate the KSeF),
  - specifying the mandatory data for the different types of sales invoices as well as corrective invoices / advance invoices to be sent to KSeF once e-invoicing becomes mandatory,
  - specifying optional data on sales invoices and the rules for making it available to contractors (on the e-invoice or outside KSeF),
  - defining the rules for issuing and making available sales invoices to foreign counterparties,
  - defining the rules for issuing and making available sales invoices to consumers,
  - defining rules for the workflow/acceptance of purchase invoices.

NOTE: It is recommended that the basis for the preparation of the internal invoicing procedure should be the previously drawn invoicing process map, the planning of sales and service processes and the data provided by the company.

5. Tax consultations concerning KSeF / Support in dealing with the tax administration

• We also offer ongoing, tax-related consultations at the various stages of e-invoicing implementation, as well as support in dealing with the tax administration on KSeF-related matters (e.g. assistance in granting authorizations to operate KSeF / preparation of explanations for queries from the tax authorities, etc.).

 Additional diagnostics for e-invoice implementation

Once the obligation to issue e-invoices comes into force, the tax authorities will gain the ability to verify transactions, and therefore taxpayers' VAT settlements, more quickly and accurately.

As part of the implementation work, we offer the possibility to carry out a VAT audit, which would be oriented towards verifying, in the context of the applicable VAT regulations, the correctness of the current procedures regarding the issuing of sales invoices and the deduction of VAT from purchase invoices in order to minimize the risk of VAT sanctions/ VAT assessment should the company be subject to a possible VAT inspection.

VAT audit

• In particular, the audit would cover the rules applied by the taxpayer with respect to the following issues:
  - determining tax point,
  - place of supply,
  - taxable amount,
  - the allocation of VAT rates,
  - inclusion of transactions under the reverse charge mechanism,
  - the application of special procedures,
  - deduction of VAT.
• The aim of our work would be to ensure that the KSeF system is implemented on the basis of already existing, correct and proven principles of VAT methodology and settlement.
• The audit would be carried out on a limited sample of selected invoices and source documents.
• Our work would result in a report indicating the identified VAT risks and recommendations on how to mitigate them in advance - i.e. prior to the implementation of e-invoicing.