KSeF payment obligation from 1 August 2026: invoice number required in bank transfers
Warsaw, 30 June 2026 – From 1 August 2026, a new KSeF payment obligation applies in Poland: for payments made through the split payment mechanism (mechanizm podzielonej płatności), the KSeF reference number of the underlying invoice must be included in the payment title of the bank transfer. For companies purchasing goods or services from Polish suppliers, or issuing invoices in Poland themselves through the Krajowy System e-Faktur (KSeF), this means a concrete change to payment processes that must be operational by 1 August.
What exactly changes under the KSeF payment obligation
Poland has been rolling out its KSeF mandate in phases since February 2026, when large taxpayers were first required to connect, followed by most other businesses in April 2026. The new payment rule is an additional step that closes the loop between invoicing and payment. For split payment transactions, the obligation applies from 1 August 2026; for regular bank transfers outside the split payment mechanism, a similar requirement follows from 1 January 2027. No penalties will be imposed before the relevant start date, as long as a business can demonstrate it made reasonable and timely preparations.
In practice, this means the full 35-character KSeF number, made up of the invoice issuer’s NIP number, issue date and a technical checksum, must be copied into the “payment title” field of the transfer. For a single payment covering multiple KSeF invoices, businesses instead use the collective identifier generated through the KSeF system API. Accounting and ERP systems that automatically match payments to invoices will therefore need to correctly read and pass on this field.
Consequences for Dutch and Belgian businesses
For companies in the Netherlands and Belgium that purchase goods or services from Polish suppliers, or that invoice through a Polish subsidiary, this is a direct operational change. Finance departments and shared service centres processing payments to Polish creditors need to verify whether their payment software can correctly handle the KSeF number in the payment title field. For businesses working with a Peppol Serviceprovider, it is worth checking whether the AP/AR connection in use already supports this Polish requirement, since KSeF is a national system that exists alongside the Peppol network and does not use exactly the same data structure.
Companies looking to understand how this Polish regulation fits into their broader e-invoicing strategy can combine it with the earlier experience Peppol.now described in the article on Poland’s first weeks with KSeF and what the April deadline meant, which also explains how KSeF relates to the wider international e-invoicing landscape in which Peppol plays a central role.
What businesses should do now
Companies that receive or issue invoices through KSeF should start mapping out now which payment processes are affected. Concretely, this means checking whether the accounting package or banking environment in use can automatically place the KSeF number in the payment title, testing with a limited number of transactions before 1 August, and actively informing Polish trading partners about the new requirement. For businesses invoicing internationally across multiple national systems at once, a clear overview of the differences between KSeF, Peppol and other national platforms remains essential to avoid duplicate processes.
For most companies this is not cause for alarm, but it does call for planning. The grace period before the actual start date leaves a few weeks to adjust and test payment processes, but waiting until just before 1 August increases the risk of misallocated payments and delayed accounts payable processing. Shared service centres handling payments across several countries in particular should explicitly include this Polish requirement in their implementation planning, alongside the broader ViDA and Peppol developments taking place elsewhere in Europe.
- Podatki.gov.pl: Numer KSeF i zbiorczy identyfikator
- KSeF-gov.pl: changes to invoice payment transfers under KSeF
- Tax Insight: obligation to include the invoice number in transfers and payment allocation
Compare Peppol Serviceproviders on Peppol.now to find out which provider best supports international AP/AR integrations, including Polish KSeF connections.
