# XV-AT-04

Source: https://xmlvalid.com/rules/XV-AT-04

> The supplier number the federal government assigns (Lieferantennummer) is missing: e-Rechnung.gv.at reads it from the seller identifier (BT-29, cac:PartyIdentification/cbc:ID of the seller).

- Level: error
- Rule sets: e-Rechnung.gv.at checks (UBL) Fehlerliste, October 2026
- Context: `/ubl:Invoice | /cn:CreditNote`
- Test: `normalize-space(($supplier/cbc:CustomerAssignedAccountID, $supplier/cac:Party/cac:PartyIdentification/cbc:ID)[normalize-space(.) != ''][1]) != ''`

Validate a document against these rules: https://xmlvalid.com/validate