# GR-R-004-1

Source: https://xmlvalid.com/rules/GR-R-004-1

> When Supplier is Greek, there must be one MARK Number

- Level: error
- Rule sets: Peppol BIS Billing 3.0 rules 3.0.21
- Context: `/ubl-invoice:Invoice[$isGreekSender and ( /*/cac:AccountingSupplierParty/cac:Party/cac:PostalAddress/cac:Country/cbc:IdentificationCode = 'GR')] | /ubl-creditnote:CreditNote[$isGreekSender and ( /*/cac:AccountingSupplierParty/cac:Party/cac:PostalAddress/cac:Country/cbc:IdentificationCode = 'GR')]`
- Test: `count(cac:AdditionalDocumentReference[cbc:DocumentDescription = '##M.AR.K##'])=1`

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