KSeF and Italian SdI system: comparing mandatory e-Invoicing models in Poland and Italy

The KSeF and Italian SdI system comparison is one of the most important reference points for businesses seeking to understand the direction of mandatory e-invoicing in Europe. Poland is implementing the National e-Invoicing System (KSeF) as a central platform for issuing and receiving structured invoices. Italy, in turn, has been using Sistema di Interscambio (SdI) for several years, making it one of the most frequently analysed examples of mandatory e-invoicing in the European Union.

For entrepreneurs, investors and international groups, comparing these two systems is not only a technical exercise. It is about understanding how e-invoicing changes the entire invoice lifecycle: sales processes, accounting workflows, data control, communication with contractors and VAT compliance.

The Italian model shows that mandatory e-invoicing can, over time, become a standard part of doing business. However, the first stages of implementation usually require companies to organise their data, procedures and financial systems. This is particularly important for international businesses operating in several jurisdictions and adapting to different national e-invoicing models.

National e-Invoicing System (KSeF) in Poland and Sistema di Interscambio (SdI) in Italy as centralised platforms

Both Poland’s National e-Invoicing System (KSeF) and Italy’s Sistema di Interscambio (SdI) are examples of centralised e-invoicing systems. This means that an invoice is no longer treated only as a document sent directly from the seller to the buyer. A state-controlled platform becomes part of the invoice circulation process, and the document must pass through that platform in accordance with specific rules.

In practice, the centralised model changes the moment when an invoice is created, validated and circulated. Businesses should not treat an e-invoice as a simple PDF file sent to a customer. What matters is whether the invoice complies with the required structured format and whether it has been submitted through the correct channel.

What is the National e-Invoicing System (KSeF) in Poland?

The National e-Invoicing System (KSeF) is Poland’s state platform for issuing, sending, receiving and storing structured invoices. An invoice in KSeF has a defined logical structure and is issued in XML format. From 1 February 2026, the applicable structured invoice schema is FA(3).

KSeF is being implemented in stages. From 1 February 2026, the obligation applies to the largest taxpayers whose gross sales value in 2024 exceeded PLN 200 million. From 1 April 2026, it will apply to other taxpayers, with transitional rules provided for the smallest values of invoiced sales. In practice, 2026 is both an adjustment period and the moment when companies should realistically test their sales, accounting and document control processes.

What is the Italian Sistema di Interscambio (SdI)?

Sistema di Interscambio (SdI) is Italy’s electronic invoice exchange system managed by the Italian tax administration. In domestic transactions in Italy, electronic invoices pass through SdI, which is responsible for their formal validation and delivery to the recipient.

The Italian system is based on the FatturaPA format. Initially, it was used for transactions with public administration bodies and was later extended to domestic B2B and B2C transactions. Since 2019, Italy has been one of the key EU examples of a country where mandatory e-invoicing covers a broad range of business activity.

Key similarity: tax administration becomes part of the invoice flow

The main similarity between the National e-Invoicing System (KSeF) in Poland and Sistema di Interscambio (SdI) in Italy is that both systems bring the tax administration closer to the day-to-day invoice circulation process. In the traditional model, a business issued an invoice, sent it to the customer, and reported tax data later, for example in VAT returns, SAF-T files or other reporting documents.

In the centralised model, the invoice must be prepared in the required structure and sent to the system. Only after meeting specific conditions can it function in business circulation according to the rules of the relevant country. As a result, formal or technical errors may affect not only accounting but also the sales process itself.

For companies, this means that errors must be detected earlier. Data control can no longer take place only at month-end closing. It should be built into the invoice issuing process.

Key differences between the National e-Invoicing System (KSeF) and Sistema di Interscambio (SdI)

Although KSeF and SdI are both centralised systems, they are not identical. They differ in terms of scope of obligations, invoice format, maturity level, market practice and legal environment.

1. Implementation stage and market experience

The greatest difference is the level of system maturity. Italy has been using mandatory e-invoicing for several years. This means that Italian businesses, accounting offices, software providers and the tax administration have already gone through the adaptation phase.

In Poland, the National e-Invoicing System (KSeF) enters the mandatory phase only in 2026. For many companies, this will be the most significant change in invoicing processes in years. Implementation should not be treated purely as an IT project. It is also an organisational, tax and accounting project.

The Italian experience shows that, after the transition period, e-invoicing can streamline document circulation and reduce manual work. However, this requires well-prepared master data, clear procedures and defined internal responsibilities.

2. Invoice format

The Polish National e-Invoicing System (KSeF) uses the FA(3) logical structure. This is the Polish structured invoice schema that defines invoice elements, mandatory fields, conditional fields and the way data is presented in an XML file.

The Italian SdI system uses the FatturaPA format. It is also an XML structure, but it is designed according to Italian legal and technical requirements. A company operating in both Poland and Italy cannot therefore assume that one invoice structure will support both markets without proper data mapping.

In practice, international businesses should pay particular attention to:

• compliance of contractor data with local requirements,
• correct VAT rates and tax codes,
• fields required only in specific situations,
• handling of corrective invoices and special invoice types,
• integration of ERP systems with local e-invoicing platforms.

3. Moment of invoice validation

In both models, the central system validates invoices, but the scope and practical consequences of this validation depend on the legal and technical rules of each country. In Italy, an invoice must pass through SdI. If it is not correctly submitted through the system, it may be treated as not issued.

In Poland, the National e-Invoicing System (KSeF) also requires the submitted file to comply with the logical structure. A file containing errors, such as missing mandatory fields, may be rejected. This is directly relevant for companies that currently issue invoices in sales systems and verify data accuracy only later.

Under the KSeF model, an incorrect invoice is not only an accounting problem. It may become an operational issue if the document is not successfully submitted to the system.

4. Invoice storage and access

The National e-Invoicing System (KSeF) provides for the storage of structured invoices in the system. This may reduce some technical obligations on the company’s side, but it does not release the business from responsibility for the accuracy of data, accounting processes and evidence required for tax purposes.

In Italy, the administration also provides services related to electronic invoicing, including the preparation, sending, receiving and storage of invoices. In practice, companies still often use their own ERP systems, document workflow tools and external service providers to ensure control, integration and compliance with internal processes.

For entrepreneurs, the key distinction is clear: a state platform may store invoices, but it does not replace the company’s complete accounting, tax and internal control process.

Comparison table: National e-Invoicing System (KSeF) vs Italian SdI system

Area	Poland – National e-Invoicing System (KSeF)	Italy – Sistema di Interscambio (SdI)
System model	Centralised e-invoicing system	Centralised electronic invoice exchange system
Main function	Issuing, receiving and storing structured invoices	Receiving, validating and forwarding electronic invoices
Format	FA(3) structure, XML	FatturaPA, XML
Implementation stage	Mandatory implementation from 2026, in stages	Mandatory domestic e-invoicing in place since 2019
Business impact	Need to adapt systems, data and procedures	Established market standard after the adaptation period
Main risk	Invoice rejection due to structural errors or non-compliant data	Incorrect submission or irregularities in invoice data
Accounting impact	More automation, but also greater need to control source data	Developed practice of automation and integration with accounting systems
Challenge for international groups	Mapping Polish FA(3) requirements to global processes	Handling the Italian format and SdI rules within local processes

What does the Italian experience tell companies in Poland?

The Italian SdI system is often used as a reference point for Poland because it shows how mandatory e-invoicing affects the daily work of businesses. The most important conclusion is simple: the greatest challenges are not related to sending an XML file itself, but to data quality and process organisation.

Master data becomes critical

In the traditional model, many errors could be corrected after an invoice was issued or clarified with the contractor. In a centralised system, errors in data may lead to the rejection of a document or problems with its further processing.

Companies should therefore verify contractor data, tax identification numbers, addresses, VAT rates, country codes, transaction markings and rules for issuing corrective invoices. This becomes particularly important in sales processes where data is entered by several departments or collected from multiple systems.

Accounting must be closer to the sales process

The National e-Invoicing System (KSeF) changes the relationship between sales and accounting in Poland. An invoice is no longer only the final output of the sales process. It becomes a document that must meet technical and tax requirements at the moment of issue.

Therefore, KSeF implementation should involve not only the finance department, but also sales, customer service, logistics, IT and employees responsible for master data. In international companies, cooperation with headquarters is also necessary, as local e-invoicing requirements may require changes in the global ERP system.

In this area, support in VAT advisory in Poland may be helpful, especially where a company handles domestic and cross-border transactions and must correctly determine which documents fall under the KSeF obligation.

Automation does not remove responsibility

E-invoicing may significantly reduce manual work, accelerate document circulation and improve control over settlements. However, it does not mean that the system will automatically solve all tax issues.

Automation works well only when input data is correct. If an ERP system contains incorrect contractor data, outdated tax rules or incorrect field mapping, the National e-Invoicing System (KSeF) may simply reveal the problem faster.

For this reason, e-invoicing implementation should be combined with a review of accounting and tax processes. For foreign companies operating in Poland, it is also important to correctly allocate responsibilities between the local team, headquarters and external accounting provider. In such cases, well-organised accounting services in Poland are practical not only for document recording, but also for data compliance control.

KSeF and SdI in the context of European VAT digitalisation

The comparison between Poland and Italy should be seen as part of a broader process. The European Union is moving towards greater VAT digitalisation, faster data reporting and gradual harmonisation of e-invoicing. However, Member States are not implementing identical solutions.

Different models operate across Europe:

• centralised systems where invoices pass through a state platform,
• decentralised models where invoices are exchanged between businesses through certified platforms,
• hybrid solutions combining e-invoicing with data reporting,
• document exchange models based on networks such as Peppol.

Poland and Italy are among the countries that have chosen a strongly centralised model. Germany, France and Belgium are developing different approaches from Poland and Italy. France bases its reform on platforms accredited by the state, Belgium uses a model of structured invoice exchange between businesses that is strongly linked in practice to the Peppol network, while Germany is implementing obligations in stages without a central platform comparable to KSeF or SdI.

For entrepreneurs, this means that preparing for one system is not enough. Companies operating in several countries should build processes capable of handling different formats, implementation timelines and validation rules.

Importance for companies operating in Poland and Italy

Companies operating in both Poland and Italy should avoid the oversimplification that KSeF is a one-to-one Polish equivalent of SdI. The systems are similar in terms of central architecture, but they differ in technical and legal details.

In practice, several areas should be analysed carefully.

Data mapping between systems

If a corporate group uses one ERP system for several countries, it is necessary to verify whether the data required by the National e-Invoicing System (KSeF) and SdI is available in the correct fields. This includes, among others, tax identification numbers, buyer data, country codes, VAT rates, payment terms, correction-related data and information required only for specific types of transactions.

Correction and error procedures

Every e-invoicing system requires a procedure for handling errors. A company should know who is responsible for analysing invoice rejections, who corrects the data, who communicates with the contractor and how the document is resubmitted. A lack of such a procedure may lead to invoicing delays, cash-flow issues and inconsistencies in accounting records.

Cross-border transactions

KSeF and SdI focus primarily on domestic requirements. In international transactions, businesses must also analyse the place of taxation, contractor status, fixed establishment, registration obligations and documentation requirements.

This is particularly important for foreign companies that have a branch, subsidiary, warehouse, service centre or fixed establishment in Poland. In such cases, KSeF may become part of a broader VAT analysis, rather than only a technical invoicing obligation. Support through tax advisory services in Poland may help organise both local and cross-border obligations.

How to prepare your company for the National e-Invoicing System (KSeF) using Italian experience

The Italian example shows that effective e-invoicing implementation requires preparation in advance. Companies that limit the project to technical integration often encounter problems already at the stage of everyday system use.

1. Audit your invoice data

The first step should be a review of the data used to issue invoices. Companies should check whether contractor data is complete, up to date and compliant with KSeF requirements. It is also worth verifying whether the system correctly handles advance invoices, final invoices, corrective invoices, collective invoices and documents issued under non-standard sales models.

2. Check ERP compliance with FA(3)

The National e-Invoicing System (KSeF) requires the FA(3) structure. If a company uses a centrally implemented ERP system, it should verify whether the software provider supports Polish requirements and enables correct data mapping. Particular attention should be paid to mandatory and conditional fields.

3. Define responsibility for errors

In a centralised system, invoice rejection should not create organisational uncertainty. A company should establish a clear procedure: from error identification, through data correction, to resubmission and communication with the contractor.

4. Test the process before the full obligation applies

Testing should not be limited to a single scenario. It is worth checking different invoice types, contractor groups, domestic and foreign transactions, corrections and non-standard cases. Only such tests show whether the process is operationally ready.

5. Use KSeF implementation to organise VAT settlements in Poland

The National e-Invoicing System (KSeF) will increase the visibility of invoice data for the Polish tax administration. Therefore, implementation should be combined with a broader VAT compliance review. This includes checking VAT rates, markings, the tax point, transaction documentation and consistency of data with JPK_VAT, Poland’s SAF-T VAT reporting file.

Is Poland repeating the Italian model?

Poland is not directly copying the Italian system, but it follows a similar logic of centralised e-invoicing. In both cases, the tax administration becomes an important part of the invoice circulation process. However, the systems differ in terms of format, detailed requirements, domestic legal environment and maturity level.

Italy is an example of a market that has already gone through the adaptation process. Poland is at the stage where businesses still need to adjust procedures, systems and responsibilities. This means that companies should treat the National e-Invoicing System (KSeF) as a structural change, not only as a technical obligation. The greatest benefit of comparing KSeF and SdI is the practical conclusion it offers: mandatory e-invoicing requires high-quality data, clear procedures and close cooperation between accounting, tax, sales and IT teams.

The KSeF and Italian SdI system comparison shows two centralised e-invoicing models and the direction of change in European VAT compliance. Both systems strengthen the role of tax administration in the current flow of invoices, increase the importance of source data and require greater process discipline from businesses.

For Polish companies, the Italian experience is particularly valuable. It shows that, after the implementation period, e-invoicing can become a standard and a basis for automation. At the same time, it confirms that preparation should include not only technical integration, but also tax, accounting and organisational control. International companies should analyse the National e-Invoicing System (KSeF) not only as a local Polish obligation, but as part of the broader European transformation of VAT settlements. The earlier they organise their data, procedures and responsibilities, the lower the risk of errors after the full transition to mandatory e-invoicing in Poland.