KSeF Advance and Final Invoices in Poland in 2026

You issue advance and final invoices in the national e-invoicing system (KSeF) using the same FA(3) structure, but you must link the documents correctly. If an earlier advance invoice was an e-invoice, the settlement document must include its KSeF number, not just the number assigned in your own software.

The short answer

If you receive part of the payment before performing a service or delivering goods, you will usually document it with an advance invoice. You do not, however, have to issue a separate advance invoice if you receive the payment in the same month in which you perform the service or deliver the goods, except for transactions subject to the special deadlines in Article 106i(3)–(8) of the VAT Act. In that case, you issue one sales invoice containing the required information about the payment received.

If the advance payment was documented separately, after fulfilling the order you issue a final invoice that:

• reduces the amount due by the advance payments received,
• reduces VAT by the tax shown on the advance invoices,
• identifies the KSeF numbers of earlier advance e-invoices,
• retains its own document number assigned in your numbering series.

If the advance payment covered the full price and was documented in full, the rules do not require a separate final invoice merely to report the same sale again.

When an advance invoice is created

An advance invoice documents a payment received before goods are delivered or a service is performed. This may be:

• a deposit,
• a prepayment,
• the first instalment,
• another part of the price,
• full payment received in advance.

A pro forma invoice is not an invoice and does not document the receipt of money. If the customer has only accepted an offer but has not yet paid, there is no advance invoice to send to KSeF on that basis.

The VAT Act also identifies transactions for which an earlier payment does not follow the typical advance-invoice scheme. Before issuing a document automatically, therefore, check the type of transaction, especially for cross-border settlements and services accounted for over specific periods.

Check separately whether the payment and the sale fall in the same month. In that case, the exception under Article 106b(1a)–(1b) may apply instead of two separate invoices.

Does an advance invoice go to KSeF?

If the seller is required to issue a particular invoice through KSeF, this also applies to an advance invoice. The document is created as XML compliant with FA(3), sent to the system, and assigned a KSeF number once accepted.

You need to distinguish among three identifiers:

1. your own advance invoice number, for example FZ/18/07/2026,
2. the KSeF number assigned after the document is accepted,
3. the order, contract, or booking number used operationally.

None of these replaces the others. In particular, the KSeF number does not replace your own invoice numbering.

How to issue a final invoice

Once the service has been performed or the goods delivered, your software should collect all payments assigned to the order. The final invoice then shows the transaction’s full value and settles the amounts already documented.

Before sending it, check:

• the value of the entire order,
• the total advance payments received,
• the net and VAT amounts from each advance payment,
• the date on which the service was performed or the goods delivered,
• the KSeF numbers of the advance invoices,
• your own numbers for advance invoices that were not e-invoices,
• the amount still payable.

If an earlier advance invoice was issued through KSeF, the settlement invoice should contain its KSeF number. If the earlier document was lawfully issued outside KSeF, provide the number assigned by the seller.

The FA(3) structure includes a FakturaZaliczkowa section for identifying earlier documents. According to Ministry of Finance guidance, this element may occur up to 100 times. This matters for contracts settled through many instalments.

Several advance payments for one order

With two or more payments, do not add them up manually without checking the source documents. Each advance payment may have its own date, number, taxable amount, and VAT.

If the last advance invoice documents the remaining payment and, together with the earlier invoices, covers the full price, it should identify the numbers of those earlier advance invoices. If an amount remains to be settled after the supply has been completed, issue a final invoice and link it to all earlier advance payments.

In practice, it is worth maintaining an unambiguous chain:

order → payment → advance invoice → KSeF number → final invoice.

This means your accountant does not have to reconstruct the payment history from the bank statement alone.

What to do when an advance invoice has been corrected

Once KSeF accepts an invoice, you do not edit or delete it. You correct an error with a corrective invoice.

Before issuing the final invoice, check not only the original advance invoice but also any corrections to it. The settlement should use the current values after corrections. Otherwise, the final document may charge part of the VAT again or show an incorrect amount payable.

If KSeF rejected the advance-invoice file on technical grounds, it received no KSeF number and did not become an e-invoice. You must correct the file and send it again. You do not issue a correction for a document that the system never accepted.

An advance payment in a foreign currency

For a payment in euros or another currency, the software must correctly determine the values required in PLN. The VAT exchange rate follows the VAT Act and does not necessarily match the rate later used to account for revenue for income tax (PIT) purposes.

Do not enter one exchange rate “for all accounting” without checking the date the advance payment was received, the document’s issue date, and the date the supply was completed. KSeF will accept technically correct XML, but it will not confirm that the exchange rate or tax point is correct.

You can read more about foreign documents in KSeF and intra-EU supplies, intra-EU acquisitions, and imported services.

An advance invoice issued in offline mode

You may issue an advance invoice in the appropriate offline mode if you meet that mode’s requirements. It must still comply with the FA(3) structure, include the required markings, and be submitted to KSeF by the deadline.

Preparing an ordinary PDF and manually adding a KSeF number later is not enough. When providing the document to the buyer outside the system, you must also use the appropriate QR codes.

We explain the deadlines separately in KSeF offline24, failures, and unavailability.

Common mistakes

1. Treating a pro forma invoice as an advance invoice.
2. Issuing the final invoice for the full amount without deducting advance payments.
3. Deducting the gross value without correctly settling the taxable amount and VAT.
4. Providing only your own advance invoice number even though the document has a KSeF number.
5. Omitting one of several instalments.
6. Failing to account for a correction to an earlier advance invoice.
7. Issuing an unnecessary final invoice after a full prepayment has already been documented correctly.
8. Assuming that KSeF’s acceptance of the XML confirms the document’s tax correctness.

Checklist before sending

• Has the payment actually been received?
• Is this transaction subject to the standard rules for advance payments?
• Does your own number match your numbering series?
• Do the net, VAT, and gross amounts match the payment?
• Does the final invoice cover the order’s full value?
• Have all earlier advance payments and their corrections been deducted?
• Have you entered the KSeF numbers of earlier e-invoices?
• Have you checked the submission status and KSeF number?

We explain the full technical process in the guide on how to issue an invoice in KSeF.

Sources

• Ministry of Finance: KSeF 2.0 questions and answers
• Ministry of Finance: KSeF 2.0 materials and manuals
• VAT Act — ELI
• Consolidated text of the VAT Act — ELI, in particular Article 106b(1a)–(1b) and Article 106i(3)–(8).

Want to organise advance payments before KSeF?

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Write to Paweł or see Oxyok bookkeeping.

This material is general in nature. The correct documentation method depends on the type of transaction, the timing of payment, and the rules applicable to the particular supply.