E-invoicing in Poland and the UK: comparing KSeF with UK rules

E-invoicing in Poland and the UK follows two different regulatory timelines. Poland introduced the mandatory National e-Invoicing System (KSeF) in stages from 1 February and 1 April 2026. In the UK, electronic invoicing is still generally optional, but all VAT invoices will have to be issued and received electronically from April 2029. International groups should therefore establish one consistent invoice-data model while maintaining separate compliance processes for Poland and the UK.

E-invoicing in Poland and the UK should not be treated as a single technology project rolled out simultaneously in both countries.

Poland already operates a mandatory clearance system under which qualifying invoices must be submitted to the National e-Invoicing System (KSeF) administered by the Polish Ministry of Finance (MF). The UK currently allows businesses to choose between paper and electronic VAT invoices, although mandatory e-invoicing for all VAT invoices is scheduled to begin in April 2029.

The final UK architecture has not yet been determined. HM Revenue & Customs (HMRC) and the Department for Business and Trade are working with stakeholders on the technical standards, transmission model and implementation process. A detailed roadmap is expected at Budget 2026. For groups operating in both jurisdictions, the practical objective is not to build one identical country solution. It is to create a common invoice-data foundation supported by separate technical and compliance modules for Poland and the UK.

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What are the main differences between e-invoicing in Poland and the UK?

Area	Poland	United Kingdom
Current status	KSeF is mandatory for most taxpayers within the scope of Polish invoicing rules	E-invoicing remains generally optional; mandatory e-invoicing for VAT invoices will apply from April 2029
Mandatory implementation date	1 February 2026 for the largest taxpayers and 1 April 2026 for other taxpayers within scope	April 2029 for all VAT invoices
System model	Centralised system administered by the Polish Ministry of Finance	The final system model has not yet been confirmed
Invoice format	Structured invoice compliant with the KSeF logical schema	XML, EDI and PDF are currently permitted; the future mandatory standard has not yet been determined
Invoice transmission	The invoice is submitted to KSeF and assigned a unique KSeF number	The invoice is currently transmitted directly to the customer
Customer consent	For mandatory KSeF invoices, customer consent is not required for the invoice to be issued through the system	The customer must currently agree to receive electronic invoices
Role of the tax authority	The tax administration’s system participates directly in the invoice-issuance process	HMRC does not currently approve VAT invoices before they are delivered to customers
Storage	Structured invoices are stored in KSeF for 10 years from the end of the year in which they were issued	VAT records generally have to be retained for at least six years
Making Tax Digital or tax reporting	KSeF is a separate mandatory invoicing channel	Making Tax Digital for VAT concerns digital records and VAT returns but is not currently an e-invoicing clearance system

Poland uses a clearance model: the invoice is transmitted to a central government platform and becomes available through KSeF after successful processing.

The UK currently relies primarily on direct document exchange between the supplier and customer. Although businesses may issue electronic invoices in structured formats such as XML or Electronic Data Interchange (EDI), HMRC also recognises unstructured electronic documents such as PDFs under the current rules.

The UK government has confirmed that mandatory e-invoicing will cover all VAT invoices from April 2029. However, it has not yet published the complete data standard, transmission architecture, reporting model or transitional arrangements.

Implementation timeline

E-invoicing: Poland vs the United Kingdom

Poland — KSeF (mandatory clearance)

• 1 February 2026
  Taxpayers whose gross sales, including VAT, exceeded PLN 200 million in 2024.
• 1 April 2026
  Other taxpayers within the mandatory KSeF scope.
• 1 January 2027
  Smallest taxpayers covered by the temporary PLN 10,000 gross monthly threshold in 2026.

United Kingdom — Mandate from April 2029

• Currently
  E-invoicing generally optional; paper or electronic VAT invoices both permitted.
• Budget 2026
  Detailed implementation roadmap expected with the UK Budget 2026.
• April 2029
  All VAT invoices must be issued and received electronically.

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How does KSeF differ from electronic invoicing in the UK?

The National e-Invoicing System (KSeF) is a central platform administered by the Polish Ministry of Finance. A supplier within the mandatory scope sends a structured XML invoice to KSeF for validation and processing.

Current UK e-invoicing generally means transmitting an invoice electronically and directly to the customer. There is no general requirement to submit every private-sector VAT invoice to HMRC before or at the time it is delivered.

The distinction is not limited to file format.

In Poland, successful submission to KSeF is part of the legal invoicing process. Once the document has been accepted, the system assigns a unique KSeF number and generates an official confirmation of acceptance. In the UK, businesses can currently use PDF, XML, EDI or another electronic format that meets HMRC requirements.

They must ensure:

• authenticity of origin;
• integrity of invoice data;
• legibility;
• appropriate business controls;
• a reliable audit trail; and
• customer consent to electronic invoicing.

From a chief financial officer’s perspective, the allocation of responsibility is fundamentally different:

• in Poland, the process must include communication with the government platform, rejected-invoice handling and statutory offline procedures;
• in the UK, current responsibilities focus on internal controls, agreeing the delivery format with the customer and preserving an adequate audit trail;
• from April 2029, the UK regime will become more prescriptive, but businesses should not assume that it will replicate the Polish clearance model.

Two different models

Clearance versus direct exchange

• Poland — KSeF

  Mandatory clearance model
  Role of tax authority

  The tax administration’s system participates directly in the invoice-issuance process.

  Invoice format

  Structured invoice compliant with the KSeF logical schema.

  Transmission

  Submitted to KSeF and assigned a unique KSeF number before reaching the customer.

  Customer consent

  Not required for mandatory KSeF invoices.

  Storage

  Structured invoices stored in KSeF for 10 years from the end of the year of issue.
• United Kingdom

  Direct exchange · final model undetermined
  Role of tax authority

  HMRC does not currently approve VAT invoices before they are delivered.

  Invoice format

  XML, EDI and PDF currently permitted; future mandatory standard not yet determined.

  Transmission

  Transmitted directly to the customer.

  Customer consent

  Customer must currently agree to receive electronic invoices.

  Storage

  VAT records generally retained for at least six years.

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How does mandatory e-invoicing work in Poland in 2026?

The mandatory KSeF rollout was divided into stages:

• from 1 February 2026: taxpayers whose gross sales, including VAT, exceeded PLN 200 million in 2024;
• from 1 April 2026: other taxpayers within the mandatory scope;
• from 1 January 2027: the smallest taxpayers benefiting from the temporary PLN 10,000 monthly threshold in 2026.

Until 31 December 2026, a taxpayer may continue to issue qualifying invoices outside KSeF if the total gross value of sales documented by those invoices does not exceed PLN 10,000 in a given month. Once the threshold is exceeded, the KSeF obligation begins with the invoice that causes the threshold to be exceeded and applies to subsequent qualifying invoices.

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Which invoices must be issued through KSeF in Poland?

KSeF primarily covers invoices issued by taxpayers that:

• have their place of business in Poland; or
• have a fixed establishment in Poland that participates in the relevant supply of goods or services.

The mandatory scope generally does not include:

• invoices issued by a foreign entity that has neither its place of business nor a fixed establishment in Poland;
• invoices issued by a foreign entity that has a fixed establishment in Poland where that establishment does not participate in the transaction concerned.

Determining whether a fixed establishment exists should not be based exclusively on a Polish tax identification number or Polish VAT registration.

The assessment should consider the personnel and technical resources available in Poland, the way business decisions are made and whether the Polish structure is genuinely involved in supplying the goods or services.

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Does KSeF apply to a UK company registered for VAT in Poland?

A UK company does not automatically become liable to issue invoices through KSeF merely because it is registered for VAT in Poland.

The decisive question is whether the company has:

• its place of business in Poland; or
• a fixed establishment in Poland that participates in the specific transaction.

A UK company that only holds a Polish VAT number, without sufficient personnel and technical resources or a participating fixed establishment in Poland, will generally remain outside the mandatory KSeF invoice-issuance requirement. The conclusion may be different where the company has a Polish structure that is genuinely involved in sales, service delivery, order fulfilment or operational decision-making. For example, additional analysis may be required where the UK company has employees, an office, a warehouse, technical infrastructuree or a local operational team in Poland. Because an incorrect classification can affect both invoicing and VAT reporting, the KSeF assessment should be coordinated with a review of the business’s Polish VAT position and operating model.

Professional tax advisory services in Poland can help determine whether the company’s local resources constitute a participating fixed establishment.

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How should a KSeF invoice be delivered to a UK customer?

Where a Polish supplier is required to use KSeF, an invoice issued to a UK customer must first be correctly submitted to the Polish system. The invoice can then be delivered to the UK customer outside KSeF in an agreed format, such as a readable PDF visualisation containing the required QR code.

The UK customer does not need standard user access to KSeF. The QR code enables access to the invoice held in the system and allows the customer to verify the invoice data. The precise number and type of QR codes depend on whether the invoice has already received a KSeF number and whether it was issued using one of the statutory offline procedures.

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How does electronic invoicing currently work in the UK?

UK businesses can currently choose between paper and electronic VAT invoices. HMRC does not require every VAT invoice to be submitted to a single central platform.

An electronic invoice may use a structured format such as XML or EDI. Under the current HMRC rules, unstructured electronic documents, including PDFs, may also qualify as electronic invoices.

The business must ensure:

• authenticity of origin;
• integrity of content;
• legibility of the document;
• appropriate business controls and a reliable audit trail; and
• customer agreement to receive invoices electronically.

However, current HMRC rules must be distinguished from the regime planned for April 2029.

The UK government defines future e-invoicing as the direct digital exchange of invoice data between the financial systems of buyers and suppliers, allowing the information to be processed automatically. A PDF sent by email does not provide this system-to-system exchange of structured data.

How the invoice moves

Two invoice flows

Poland — standard online KSeF flow for an invoice to a UK customer

• ERP / billing system
• KSeF

  Validation & processing
• KSeF number + confirmation
• PDF + QR code to UK customer

United Kingdom — current practice

• ERP / billing system
• PDF, XML, EDI or another agreed electronic format
• Direct delivery to customer

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Under the standard online KSeF process, a qualifying invoice is first accepted by KSeF and assigned a KSeF number. A UK customer may then receive an agreed visualisation, such as a PDF with the required QR code. Statutory offline procedures follow different timing and QR-code rules.

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Is Making Tax Digital the UK equivalent of KSeF?

No. Making Tax Digital for VAT and KSeF perform different functions.

Making Tax Digital (MTD) requires VAT-registered businesses to maintain specified VAT records digitally and submit VAT returns using compatible software. MTD does not currently function as a central platform for issuing, clearing and receiving individual VAT invoices.

KSeF, by contrast, is an invoice-level system. It processes structured invoices, assigns KSeF numbers and makes invoices available to authorised recipients.

Businesses operating in both countries should therefore avoid treating MTD compliance as evidence that their software is already prepared for either KSeF or the UK’s future e-invoicing mandate.

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When will e-invoicing become mandatory in the UK?

The UK plans to require all VAT invoices to be issued and received electronically from April 2029. The obligation is expected to apply to VAT invoices used mainly in business-to-business and business-to-government transactions. The government has stated that the requirement will cover both the issuance and receipt of invoices.

An implementation roadmap is due to be published at Budget 2026. HMRC continues to work with the Department for Business and Trade, software providers and other stakeholders on the design of the regime.

The government has not yet published complete rules covering:

• the mandatory data standard;
• the invoice transmission model;
• the method or timing of any data transfer to HMRC;
• exclusions;
• transitional periods; or
• detailed implementation requirements for different categories of business.

Consultation respondents discussed decentralised four-corner and five-corner models, including solutions based on the Peppol network. However, the government has not made a final decision on the transmission model or standard.

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Will a PDF qualify as an e-invoice in the UK after April 2029?

Based on the government’s current definition, an ordinary PDF will not be sufficient. The UK consultation materials distinguish structured e-invoices from unstructured digital documents such as PDF, Word and JPEG files. Future e-invoicing is described as the direct digital exchange of structured invoice data between the supplier’s and customer’s financial systems.

This means that sending a document electronically will not, by itself, satisfy the future requirement. The data will need to be provided in a format that enables automated processing by the recipient’s financial system.

However, the final technical requirements for the April 2029 regime have not yet been published. Businesses should therefore prepare their systems to handle structured data without prematurely committing to an unconfirmed UK format.

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How should transactions between Poland and the UK be invoiced?

Example transaction	Likely invoicing approach
A Polish company supplies services to another Polish business	The invoice will generally be issued and made available through KSeF
A Polish company supplies services to a UK business	The invoice may fall within KSeF; the UK customer may receive an agreed visualisation containing the required QR code
A UK company without a place of business or participating fixed establishment in Poland supplies a Polish company	The UK supplier will generally not be required to issue the invoice through KSeF
A UK company has a fixed establishment in Poland that participates in the sale	An individual assessment is required to determine whether the KSeF obligation applies
A Polish company receives an invoice from a UK supplier	The invoice will not automatically appear in KSeF where the UK supplier is outside the mandatory scope
A transaction is made with a consumer	B2C invoices are outside mandatory KSeF; the detailed scope of the future UK mandate still requires clarification

Each scenario should also be reviewed in relation to:

• the VAT place-of-supply rules;
• VAT registrations;
• the existence and participation of a fixed establishment;
• the reverse-charge mechanism;
• applicable invoice-content requirements; and
• the VAT reporting obligations in each jurisdiction.

The treatment of an invoice under KSeF does not, by itself, determine the VAT treatment of the underlying transaction.

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How should a business operating in Poland and the UK prepare?

The most common implementation mistake is to assume that one ERP connection to an e-invoicing platform will satisfy the requirements in both jurisdictions. A more resilient approach is to establish one common invoice-data core while implementing separate country-specific compliance modules.

1. How should the scope of the obligation be mapped?

The initial scope assessment should cover:

• legal entities;
• branches;
• VAT registrations;
• fixed establishments;
• invoicing systems;
• shared service centres;
• warehouses;
• local operational teams; and
• the systems that create or amend invoice data.

UK companies with employees, warehouses, offices or operational teams in Poland require particular attention. The mapping exercise should identify not only where the invoice is generated, but also which establishment participates in the underlying transaction.

2. Which master data should be reviewed?

Businesses should verify:

• VAT numbers;
• legal names and addresses;
• customer and supplier roles;
• currencies;
• tax rates;
• payment terms;
• product and service classifications; and
• cross-border transaction indicators.

Under the Polish system, incomplete or inconsistent data can lead to technical rejection or the issuance of an invoice that later requires correction. Data validation should therefore take place before the invoice is converted into the KSeF structure, rather than only after the platform returns an error.

3. Why should invoice data be separated from the visual document?

The financial system should retain invoice data in a format that can be mapped to different country structures.

The same underlying data can then be used to generate:

• an XML file compliant with the KSeF schema;
• a future UK structured e-invoice;
• a readable invoice visualisation for the customer; and
• accounting and VAT reporting records.

This approach reduces the risk that a future change to a government standard will require the company to rebuild its entire sales and billing process. The PDF should be treated as one possible presentation layer, not as the primary source of invoice data.

4. How should errors and system unavailability be managed?

In Poland, the invoicing process must account for:

• rejected invoices;
• invoices that have not received a KSeF number;
• the offline24 procedure;
• scheduled KSeF unavailability;
• an officially announced system failure; and
• subsequent verification of documents submitted after an offline event.

Under the offline24 procedure, the invoice must be submitted to KSeF without delay and no later than the next business day after it was issued. Separate statutory deadlines apply where the system is unavailable or an official failure has been announced. During an officially announced failure, invoices must generally be submitted within seven business days after the failure ends.

The company should define:

• who reviews error messages;
• who decides whether and when the document should be resubmitted;
• how the customer receives the invoice while KSeF is unavailable;
• how offline events are documented;
• how QR codes are generated;
• how duplicate submissions are prevented; and
• how the data is reconciled after the invoice is accepted.

5. How should systems be prepared for the UK mandate without assuming the final standard?

A business does not yet need to implement a specific UK e-invoicing format because the final technical standard has not been announced.

It should nevertheless assess whether its software:

• supports XML structures or EDI standards;
• can communicate through application programming interfaces;
• preserves a complete audit trail and version history;
• can exchange data with external service providers;
• avoids relying exclusively on PDF documents;
• separates invoice data from document presentation;
• supports configurable data mapping; and
• can be adapted without replacing the entire ERP environment.

The selection of a specific UK network, platform or operator should generally wait until the government publishes sufficient technical and regulatory detail. This does not mean delaying all preparation. Businesses can already improve data quality, system interoperability and process ownership.

6. Who should own the e-invoicing process?

The implementation should involve:

• finance;
• tax;
• accounting;
• IT;
• procurement;
• sales;
• legal and compliance teams; and
• information security.

Responsibility should not be assigned solely to the accounting department or ERP provider. Finance and tax teams should determine the legal and reporting requirements. IT teams should ensure system availability, security and integration. Sales and procurement teams should manage the effect on customer and supplier processes.

A named process owner should be responsible for coordinating these functions and approving the response to regulatory or technical changes.

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What is the key conclusion for international groups?

Poland and the UK are moving towards more automated exchange of structured invoice data, but they have selected different implementation schedules and may ultimately use different technical models.

In Poland, the immediate priority is stable operation under the mandatory KSeF regime. This includes:

• handling cross-border invoices;
• determining whether foreign entities and fixed establishments fall within scope;
• managing rejections and offline procedures;
• correctly delivering invoice visualisations outside KSeF; and
• reconciling KSeF data with accounting and VAT reporting.

In the UK, the priority is to prepare invoice data, system architecture and internal governance for the April 2029 mandate.

Businesses should not yet select a UK standard based on assumptions. The final architecture, standard and transitional requirements remain under development, with further details expected in the Budget 2026 roadmap.

For an international group, the most practical design principle is: one invoice-data core, supported by separate country compliance modules. This model reduces the cost of future changes, limits dependence on a single format or provider and enables the organisation to introduce additional national e-invoicing requirements without rebuilding the entire billing process.

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Frequently asked questions about e-invoicing in Poland and the UK

Are electronic invoices currently mandatory in the UK?

A general private-sector e-invoicing obligation is not yet in force in the UK. Electronic invoicing is currently optional, provided the business meets HMRC requirements concerning authenticity, data integrity, legibility, business controls and customer consent. All VAT invoices will have to be issued and received electronically from April 2029. The detailed technical requirements and transitional timetable have not yet been published.

Does a Polish company have to send a KSeF invoice to a UK customer?

Where an invoice falls within the mandatory KSeF rules, the Polish supplier must first issue it through KSeF. The supplier may then deliver an agreed visualisation to the UK customer, typically as a readable PDF containing the applicable QR code. The customer does not require standard KSeF access. The QR code provides a method of accessing and verifying the invoice held in the Polish system.

Will a PDF be sufficient after mandatory UK e-invoicing is introduced?

Based on the current government definition, no. A standard PDF sent by email does not constitute a structured, system-to-system exchange of invoice data. It is therefore unlikely to satisfy the April 2029 requirements on its own. The final data standard and transmission requirements have not yet been published, so businesses should prepare for structured data exchange without making irreversible technology decisions at this stage.

Does a UK company need KSeF because it has a Polish VAT number?

Not necessarily. A Polish VAT registration does not by itself create an obligation to issue invoices through KSeF. The company’s place of business and any fixed establishment participating in the transaction must be assessed. A UK company with no participating establishment in Poland will generally remain outside the mandatory invoice-issuance scope, even where it is registered for Polish VAT.

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What should businesses do now?

E-invoicing in Poland and the UK differs primarily in its implementation stage and the role of the tax administration.

Poland already operates a mandatory centralised system. The UK currently maintains a more flexible model but plans to require the electronic issuance and receipt of all VAT invoices from April 2029.

Businesses operating in both jurisdictions should now:

• organise and validate invoice master data;
• identify the entities and establishments within the KSeF scope;
• document process ownership;
• implement reliable KSeF error and offline procedures;
• separate structured invoice data from PDF visualisations;
• assess whether their ERP environment supports APIs, XML and configurable mappings; and
• monitor the UK roadmap without committing prematurely to an unconfirmed technical standard.

Where there is uncertainty about the scope of KSeF, the existence of a fixed establishment or the invoicing of Polish–UK transactions, the analysis should be completed before changing the ERP configuration.

getsix® supports international companies through accounting services in Poland, VAT and tax advisory in Poland and the adaptation of finance and invoicing processes to KSeF requirements.

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