KSeF and Belgium E-Invoicing: 2026 Mandates Compared
KSeF in Poland and Belgium e-invoicing compared: 2026 go-live dates, who is in scope, Peppol vs a national platform, grace periods, penalties and what to do.
Quick answer: Belgium made structured B2B e-invoicing mandatory on 1 January 2026, using the Peppol network, with a tolerance period to 31 March 2026 and fines from €1,500. Poland's KSeF became mandatory for issuing invoices on 1 February 2026 for taxpayers with 2024 sales above PLN 200 million and on 1 April 2026 for everyone else, with penalties deferred to 1 January 2027.
KSeF and Belgium e-invoicing are the two big European mandates of 2026, and they show the two main ways countries do it. Belgium uses Peppol, an open network where invoices go directly from supplier to buyer. Poland uses KSeF, a central government platform that every invoice passes through. This guide explains both, side by side, for business owners and for foreign suppliers billing Belgian or Polish customers. Where neither mandate applies, you can still send a clear PDF from our free invoice generator.
Important: This is general information, not tax or legal advice. Both countries adjusted their rules during 2025 and 2026, and further changes (including Belgian e-reporting from 2028) are still being legislated. Check the official sources, the Belgian e-invoicing portal and the Polish KSeF portal, or ask a local adviser.
Belgium and Poland at a glance
| Belgium | Poland (KSeF) | |
|---|---|---|
| Start date | 1 January 2026 for all in-scope businesses | 1 February 2026 (largest) and 1 April 2026 (others) |
| Model | Peppol four-corner network, post-audit | Central government platform (clearance-style) |
| Format | Peppol BIS Billing 3.0 (EN 16931), other EN 16931 formats by agreement | Polish structured invoice schema, FA(3) |
| Transactions covered | Domestic B2B between Belgian VAT-registered businesses | B2B invoices by Polish taxpayers (B2C optional) |
| Grace period | Tolerance until 31 March 2026 | Penalties from 1 January 2027; micro-business relief through 2026 |
| Penalties | €1,500 first offence, rising for repeats | Penalties linked to the invoice's VAT, from 2027 |
| Next step | Real-time e-reporting planned from 2028 | Full enforcement from 2027 |
Belgium e-invoicing: who is in scope
The obligation covers domestic B2B transactions between taxable persons established in Belgium and identified for VAT. In practice that is almost every Belgian business, including small businesses using the VAT exemption scheme for small enterprises, at least for receiving e-invoices.
Out of scope or excluded:
- Sales to consumers (B2C)
- Businesses making only VAT-exempt supplies under article 44 of the VAT Code
- Flat-rate taxpayers and businesses in bankruptcy or judicial reorganisation, for issuing
- Foreign businesses without a fixed establishment in Belgium, even if VAT-registered there
- Cross-border sales, which fall under EU rules rather than this domestic mandate
Invoices to Belgian public bodies were already electronic via Peppol before 2026.
Belgium: how it works in practice
Belgium chose Peppol as the default channel. Each business registers with a Peppol access point, usually through its accounting software, and gets a Peppol ID based on its enterprise number (scheme 0208). Invoices are sent as structured XML directly to the buyer's access point. The tax authority is not in the flow today; it audits later. Our explainer on what Peppol is walks through the four corners.
A PDF emailed to a Belgian business customer is no longer a valid invoice for an in-scope domestic B2B sale. Two parties can agree to use another EN 16931-compliant format and channel, but Peppol is the one every business must be able to receive on.
Belgium tolerance period and penalties
FPS Finance announced a three-month tolerance: from 1 January to 31 March 2026, no penalties for businesses that could show they had taken timely and reasonable steps to comply but were not yet technically ready. Since 1 April 2026 the normal penalty regime applies. The fines are graduated, starting at €1,500 for a first infringement and rising for repeat infringements (€3,000 and then €5,000 are the amounts commonly cited by advisers).
Belgium's next phase: e-reporting from 2028
Belgium plans to add real-time reporting of invoice data to the tax authority via Peppol (a "fifth corner") from 1 January 2028. As of October 2026 this was in draft legislation, so treat the date as provisional.
Poland KSeF: who is in scope and when
| Group | Must issue in KSeF from |
|---|---|
| All VAT taxpayers: receiving invoices via KSeF | 1 February 2026 |
| Taxpayers with 2024 sales above PLN 200 million (including VAT) | 1 February 2026 |
| All other taxpayers | 1 April 2026 |
| Taxpayers whose invoiced sales are no more than PLN 10,000 a month | May issue outside KSeF until 31 December 2026 |
| Financial penalties | From 1 January 2027 |
KSeF covers invoices issued by taxpayers established in Poland, or with a fixed establishment there that is involved in the sale. Foreign businesses that are only VAT-registered in Poland are generally not required to issue in KSeF, though they may do so, and Polish buyers will often ask for KSeF invoices because that is where their purchase records now live. Invoices to consumers can be issued outside KSeF.
How KSeF works
- Your software creates an invoice in the official FA(3) structured format.
- It sends the invoice to KSeF, authenticated with a token, certificate or other approved method.
- KSeF validates it and assigns a unique KSeF number with a date and time.
- Your buyer retrieves the invoice from KSeF. You can also share a visualisation (PDF or print) with a QR code that links to the invoice in KSeF.
KSeF provides offline modes for when the system or your connection is unavailable: you issue the invoice with a QR code and upload it within the permitted time. The Ministry of Finance provides free basic tools (a web application and mobile app) for small businesses with low volumes. The model is clearance-style, like India's IRN system described in our India e-invoice guide.
KSeF penalties from 2027
The penalty provisions were deferred to 1 January 2027. Under the law as enacted, fines can be calculated as a percentage of the VAT on an invoice issued outside KSeF when it should have been issued in KSeF, and in some cases as a percentage of the invoice total. The details and any further changes should be checked with a Polish adviser. Even in 2026, an invoice issued outside KSeF when it should have gone through the system can create problems for both parties.
Worked example: one sale in each country
A consultancy bills a Belgian client and a Polish client for the same workshop package. Each invoice is priced in local terms.
| Belgium (€) | Poland (PLN) | |
|---|---|---|
| Workshop, 2 days | 2,400.00 | 10,400.00 |
| Materials and follow-up report | 600.00 | 2,600.00 |
| Net total | 3,000.00 | 13,000.00 |
| VAT (21% Belgium, 23% Poland) | 630.00 | 2,990.00 |
| Gross total | 3,630.00 | 15,990.00 |
| How it is sent | Peppol BIS XML via access point | FA(3) XML via KSeF, receives KSeF number |
The maths: Belgium 2,400 + 600 = €3,000; 21% = €630; total €3,630. Poland 10,400 + 2,600 = PLN 13,000; 23% = PLN 2,990; total PLN 15,990. If the consultancy is established in Belgium, the Belgian sale is domestic and must be a Peppol e-invoice. If it is not established in Poland, the Polish invoice is a cross-border supply that will usually be reverse charged by the buyer, so it would not show Polish VAT and would generally sit outside KSeF. See our reverse charge invoice guide for the wording.
Foreign suppliers: what changes for you?
- Selling to Belgium from abroad: the domestic mandate does not apply to you if you have no Belgian establishment. Your Belgian customers may still prefer Peppol invoices, and Peppol works cross-border.
- Selling to Poland from abroad: without a Polish fixed establishment you are generally not required to issue in KSeF. Expect some customers to ask anyway.
- Both: get your customers' VAT numbers right. Our VAT invoice guide and tax ID guide cover the details.
Where a free invoice generator still fits
Our generator is free, runs in your browser, saves drafts in local storage and exports PDFs. It does not create Peppol or KSeF XML, connect to an access point or submit to KSeF. It is not suitable for in-scope domestic B2B invoices in Belgium or (outside the micro-business relief in 2026) in Poland. It still works for quotes, proformas, B2C invoices and invoices outside the mandates, for example from a freelancer outside the EU. The Slate template suits those formal European invoices.
Next step
If you are established in Belgium, confirm your Peppol registration is active and that you can both send and receive. If you are in Poland, check that your software is issuing in FA(3) and that you have a plan for the end of the micro-business relief on 31 December 2026. For the bigger picture, read our e-invoicing guide and the guide to France's e-invoicing reform.
Frequently asked questions
What is KSeF?
KSeF (Krajowy System e-Faktur) is Poland's National e-Invoice System, run by the Ministry of Finance. Structured invoices are issued through KSeF, which assigns each one a KSeF number, and buyers download their purchase invoices from the same system.
When did KSeF become mandatory?
Taxpayers whose 2024 sales exceeded PLN 200 million (including VAT) had to issue invoices in KSeF from 1 February 2026, and all other VAT taxpayers from 1 April 2026. Businesses with monthly sales on invoices of no more than PLN 10,000 may issue invoices outside KSeF until 31 December 2026. All businesses have had to receive invoices via KSeF since 1 February 2026.
Are there KSeF penalties in 2026?
Financial penalties for KSeF breaches were deferred and are scheduled to apply from 1 January 2027. That does not mean an invoice issued outside KSeF in 2026 is fine; it can still cause problems for your customer's VAT deduction and your own records.
Is e-invoicing mandatory in Belgium?
Yes. Since 1 January 2026, Belgian VAT-registered businesses must exchange structured e-invoices for domestic B2B transactions, with Peppol as the default channel. Sales to consumers are not covered.
What are the penalties for not using e-invoicing in Belgium?
Belgium set graduated fines for failing to issue or receive structured e-invoices, starting at EUR 1,500 for a first infringement and rising for repeat infringements (EUR 3,000 and EUR 5,000 are the commonly cited amounts). A tolerance period ran until 31 March 2026 for businesses that could show they had taken reasonable steps to comply.
Is there a tax incentive for e-invoicing software in Belgium?
Yes. Belgium introduced an increased cost deduction of 120% for qualifying e-invoicing costs, such as software subscriptions and related advice, for SMEs and self-employed people, covering tax years 2024 to 2027. Where a package does more than e-invoicing, such as a full ERP, only the e-invoicing part may qualify. Check the conditions with your accountant or SPF Finances.
Does the Belgian mandate cover invoices to foreign customers?
No. Belgium's structured e-invoicing obligation applies to domestic B2B transactions between businesses established in Belgium. Invoices to customers in other countries, and to consumers, are outside the mandate, so a PDF is generally still acceptable unless the customer or their country requires otherwise. Belgian businesses must still be able to receive Peppol invoices from domestic suppliers.
What happens if KSeF is unavailable when I need to issue an invoice?
Poland's rules provide offline procedures. In offline24 mode you can issue the invoice outside KSeF and upload it by the next business day, and separate rules cover KSeF outages and total failure situations announced by the Ministry of Finance. Invoices delivered outside KSeF in these modes generally need verification QR codes. Check the current Ministry guidance and your software's offline support.
What is the QR code on a KSeF invoice for?
When an invoice is shown or delivered outside KSeF, for example to a consumer or a foreign customer, or as a printed copy, it carries a QR code that lets the recipient check the invoice against KSeF. Invoices issued in offline modes may need an additional certificate QR code. Your invoicing software should generate these automatically, so check it supports the current KSeF 2.0 requirements.
Do foreign companies have to use KSeF?
Foreign businesses with a fixed establishment in Poland that takes part in the sale generally fall under KSeF. Foreign businesses registered for Polish VAT without a fixed establishment are generally not obliged to issue invoices in KSeF, though they can choose to. They may still need to deal with KSeF when receiving invoices. Confirm your status with a Polish tax adviser.
Invoice Creator Editorial Team
Guides on invoicing, cash flow and small-business finance from Invoice Creator, operated by Next Software Development Company. Content is reviewed for accuracy against the fields our own invoice generator produces.
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