00001: File name not valid
What it means
SdI code 00001 means the name of the file you sent does not follow the naming rule in the SdI technical specifications.
The usual cause
The SdI technical specifications build the name from the country code, the sender's tax identifier, an underscore and a progressive of up to five letters or digits, with the extension .xml or .xml.p7m, or .zip for a compressed archive. Check each part, including the underscore.
How to fix it
Rename the file to the required pattern, for example IT01234567890_00001.xml, and send it again.
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.