450: Invoice content failed the semantic checks
What it means
KSeF invoice status 450 means the invoice failed KSeF's content checks.
The usual cause
KSeF checks that the invoice date (P_1) is not later than the date it receives the invoice and, in production, checks NIP checksums for Podmiot1, Podmiot2, Podmiot3 and PodmiotUpowazniony where present. Check these values and any details in the response.
How to fix it
Correct any errors found, for example the invoice date or a NIP, and send the invoice again.
The code as published
Błąd weryfikacji semantyki dokumentu faktury Read the official document . Source: KSeF API 2.0, specyfikacja OpenAPI (open-api.json), version 2.9.0, published by Ministerstwo Finansów, read on 8 November 2026.
Look at your file
Open the invoice in your browser to find the fields this code names: Open a Polish KSeF invoice. Open a Polish KSeF invoice