How to Issue an Invoice as a Sole Proprietor in Poland?

How to issue an invoice as a JDG (a Polish sole proprietorship) without having it bounced back? The usual story: you send an invoice, and a week later the client writes "the sale date is missing" or "wrong tax ID, please issue a correction". A missing mandatory field usually means a correction invoice, extra back-and-forth and a delayed payment.

There is a second reason to get this right now. Since 1 April 2026, most Polish businesses issue invoices through KSeF (Poland's national e-invoicing system), and on 1 January 2027 the temporary 10,000 PLN monthly threshold that let the smallest JDGs invoice the old way ends.

Below: the full list of required invoice fields, what changes for VAT-exempt businesses, how KSeF fits in, and a short checklist.

I write as a software founder who builds invoicing tools, not as a tax advisor. Everything here is based on the law and Ministry of Finance (MF) announcements, with links. For disputed cases, ask your accountant or check an official tax ruling.

When a JDG must issue an invoice, and by when

Sales to another business are documented with an invoice. A private individual (a consumer) gets one on request. The rules come from the Polish VAT Act.

Deadline: you issue the invoice by the 15th day of the month following the month of delivery of the goods or completion of the service (Art. 106i of the VAT Act). You can also issue it early, up to 30 days before delivery or completion.

Example: you completed a service on 20 October 2026. The invoice is due by 15 November 2026 at the latest.

Required invoice fields under Art. 106e of the VAT Act

The list of mandatory fields is in Art. 106e(1) of the VAT Act. For a typical JDG invoice it comes down to this:

What is not required: the words "original" and "copy", or the title "VAT invoice". An invoice without them is valid, and the buyer keeps the right to deduct VAT.

In specific situations extra markings apply, for example "cash accounting method", "self-billing", "split payment mechanism" and reverse charge (Art. 106e(1) points 16–24). The law does not require a payment due date or a bank account number, but without them the client cannot pay you, so always add them.

Invoices from a VAT-exempt JDG

If you use a VAT exemption, your invoice shows no VAT rate and no VAT amount. Instead there is one more duty: state the legal basis of the exemption (Art. 106e(1) point 19), for example a specific article of the VAT Act.

There is one exception. A taxpayer exempt from VAT because of the sales threshold (Art. 113(1) and (9)) does not have to state the legal basis. From 2026, that threshold is 240,000 PLN.

Being VAT-exempt does not exempt you from KSeF. More on that below.

How to issue an invoice as a JDG in KSeF: what changes

The timeline, without generalisations (KSeF on podatki.gov.pl):

• 1 February 2026 – receiving invoices through KSeF is mandatory for all taxpayers.

• 1 April 2026 – issuing in KSeF covers the remaining businesses, including JDGs and VAT-exempt firms.

• until 31 December 2026 – an exception for invoiced sales up to 10,000 PLN gross per month. The invoice that crosses this threshold must already go through KSeF, and there is no way back to the old rules.

• 1 January 2027 – the threshold disappears and KSeF applies to everyone.

In practice:

• An invoice is an XML file in the FA(3) structure. The system validates it, assigns a KSeF number and generates a UPO (an official confirmation of receipt).

• The KSeF number does not replace your own invoice number. They are two different numbers: yours goes into the P_2 field, the KSeF number is assigned by the system.

• The visual copy of the invoice (e.g. the PDF you send to the client) carries a QR code and the KSeF number.

• Invoices to consumers are voluntary in KSeF.

A simplified fragment of the file (not a complete invoice):

<P_1>2026-10-15</P_1>   <!-- issue date -->
<P_2>FV/10/2026/001</P_2> <!-- invoice number assigned by you -->
<P_6>2026-10-14</P_6>   <!-- date of the service -->
<P_15>6150.00</P_15>    <!-- total amount due -->

A worked example: a service for 5,000 PLN net, 23% VAT is 1,150 PLN, 6,150 PLN gross in total. In 2026 that invoice fits under the 10,000 PLN threshold, but in 2027 it has to go through KSeF.

What happens if an invoice is issued outside KSeF

Under the current text of the law, penalties apply from 1 January 2027. The cap is 100% of the VAT shown on the invoice, or up to 18.7% of the total amount due for an invoice without VAT (Art. 106ni). For the invoice above: up to 1,150 PLN.

There is an important change in progress, though. On 16 September 2026 the Ministry of Finance announced that penalties would be pushed back by a year, and on 23 September 2026 a draft act, UD477, appeared, setting their start at 1 January 2028. It is still a draft, not law. The MF also stresses that postponing penalties does not postpone the obligation to use KSeF (MF announcements).

The most common mistakes on JDG invoices

• A wrong or outdated NIP or address for the buyer.

• A missing sale date when it differs from the issue date.

• Gaps in numbering, or two invoices with the same number.

• No exemption basis on the invoice of a VAT-exempt JDG (except the Art. 113 exemption).

• Confusing the KSeF number with the invoice number.

• A PDF that differs from the XML sent to KSeF.

Checklist before you send an invoice

1. The buyer's details match the official registry (NIP, name, address).

2. The invoice number is sequential and not repeated.

3. The issue date is there, and the sale date too if it differs.

4. Description, quantity, net price, VAT rate and gross amount add up.

5. If you are VAT-exempt, the exemption basis is stated (where required).

6. You added a payment due date and a bank account number.

7. You know whether this invoice must go through KSeF, and you keep the KSeF number and UPO.

Conclusion

A correct JDG invoice is a dozen concrete fields from Art. 106e and, from 2027 without exceptions, submission to KSeF. Most mistakes happen in buyer data and numbering, exactly where people retype and calculate by hand.

That is why in Biurko buyer data is filled in from the GUS registry by NIP, numbering runs automatically, and the invoice goes to KSeF when you issue it, with the KSeF number and UPO attached. You can also issue bilingual invoices, and the interface works in Polish, Ukrainian and English. Try Biurko free for 14 days at biurko.io.

FAQ

What must an invoice issued by a JDG in Poland contain?

The issue date, a sequential number, the seller's details and NIP, the buyer's details, a description of the goods or service, unit and quantity, net price, VAT rate and amount, and the total due. If the sale date differs from the issue date, add it. The full list is in Art. 106e of the VAT Act.

Does a VAT-exempt JDG have to issue invoices in KSeF?

Yes. Since 1 April 2026 the obligation also covers VAT-exempt businesses. The exception is invoiced sales up to 10,000 PLN gross per month, but only until 31 December 2026. From 1 January 2027 KSeF applies to everyone.

What is the deadline for issuing an invoice for a service?

By the 15th day of the month following the month the service was performed. A service done on 20 October 2026 needs an invoice by 15 November 2026. You can issue it earlier, up to 30 days before the service is performed.

Does an invoice need the word "original" or "VAT invoice"?

No. The words "original" and "copy", and the title "VAT invoice", are not required, and including or omitting them does not affect whether the invoice is valid. What matters is the presence of the fields listed in Art. 106e of the VAT Act.

Do invoices to private individuals also go through KSeF?

No. Invoices to consumers are issued in KSeF voluntarily. If you choose to send such an invoice to KSeF, you must give the consumer access to it, for example through a visual copy with a QR code.