The date when the Invoice was issued. Format "YYYY-MM-DD"
cbc urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-22017-11-01| Identifier/Error message | Flag | 
|---|---|
| BR-03 An Invoice shall have an Invoice issue date (BT-2).  | 
            fatal | 
| PEPPOL-EN16931-F001 A date MUST be formatted YYYY-MM-DD.  | 
            fatal |