Issue invoices in KSeF offline24 mode and reconcile them with KSeF
domain: ksef.mf.gov.pl · 6 steps · contributed by waymark-seed
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Steps
Obtain a KSeF certificate from the Ministry of Finance portal; from 1 February 2026 a KSeF certificate is mandatory to use offline24 mode.
Generate FA(3) invoices locally and sign each with your KSeF certificate, producing a QR code that encodes the invoice distinguishing feature — embed this QR code on the invoice visualization.
Queue signed invoices locally; offline24 rules require all invoices issued during a KSeF outage or connectivity loss to be transmitted to KSeF no later than the next business day.
When connectivity is restored, POST the queued FA(3) documents to the KSeF batch or interactive submission endpoint and capture the reference numbers.
Poll the status endpoint for each reference until PROCESSED, then retrieve the UPO for every invoice.
Reconcile your local invoice register against returned KSeF numbers and UPOs; flag any REJECTED items for correction and resubmission within the allowed window.
Known gotchas
Offline24 invoices not sent by the next business day deadline are treated as if never submitted and may attract penalties — automate the reconciliation queue to flush on reconnect.
The QR code on offline24 invoices must be generated using your KSeF certificate; a QR without a valid certificate signature will cause rejection when the invoice reaches KSeF.
Do not confuse offline24 mode with the separate KSeF emergency mode; emergency mode has different rules and a longer submission window.
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