00306: Buyer's tax number not valid
What it means
SdI code 00306 means the buyer's tax number, in 1.4.1.2 CodiceFiscale, is not valid.
The usual cause
Check for a typo or a VAT number entered in the tax number field.
How to fix it
Correct the buyer's tax number and send the file again.
Elements the check reads
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1.4.1.2 CodiceFiscale
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
Other SdI codes
- 00300 Sender's tax number not valid
- 00301 Seller's VAT number not valid
- 00302 Seller's tax number not valid
- 00303 Tax representative's VAT number not valid
- 00304 Tax representative's tax number not valid
- 00305 Buyer's VAT number not valid
- 00311 Recipient code not valid
- 00312 Recipient code not active
- 00320 Seller's VAT number and tax number do not match
- 00321 Seller's tax number is not in the VAT group
- 00322 Tax number missing with a VAT group number
- 00323 Seller's VAT number closed more than five years ago
- 00324 Buyer's VAT number and tax number do not match
- 00398 Central office code used where a specific office exists
- 00399 Private-sector format used for a public body