UPO (KSeF receipt)

The official confirmation KSeF issues for received invoices, with the KSeF number and the date the invoice entered the system.

In KSeF an invoice counts as issued and received when the system accepts it and assigns a KSeF number; the UPO is the proof. Integrations download it after each sending session and store it next to the invoice, because it settles disputes about whether and when an invoice was delivered. A rejected invoice gets an error instead and has to be corrected and sent again.

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Related terms

KSeF (Polish National e-Invoice System): Poland’s central system for structured e-invoices: invoices are sent as FA(3) XML and receive a KSeF number.
KSeF offline modes: Ways to issue invoices when KSeF or your connection is down, then send them later, marked with QR codes.
Webhook: An HTTP request one system sends to another when something happens, instead of the other system asking repeatedly.

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