00404: Duplicate invoice
What it means
SdI code 00404 means this invoice matches a previously processed invoice under the duplicate checks. No notification of rejection by SdI or refusal by the recipient was sent for that earlier invoice.
The usual cause
Check whether you sent the same invoice twice or reused its number for the same seller and year. The detailed check also considers TipoDocumento (including TD04), Art73 and SoggettoEmittente.
How to fix it
Check the earlier invoice and its submission status before sending anything again. If this is a different invoice with a reused number, give it a new number and send it again.
Elements the check reads
-
1.2.1.1 IdFiscaleIVA -
2.1.1.1 TipoDocumento -
2.1.1.3 Data -
2.1.1.4 Numero
The code as published
Read the official document . Source: Elenco dei controlli effettuati sul file fattura del Sistema di Interscambio, version 2.0, published by Agenzia delle Entrate, fatturapa.gov.it, read on 8 November 2026.
Klarbon explains each code in its own words; the official wording is in the document linked above.
Look at your file
Open the invoice in your browser to find the fields this code names: Open an Italian FatturaPA invoice. Open an Italian FatturaPA invoice