GR-R-004-1: When Supplier is Greek, there must be one MARK Number

StandardPeppol BIS Billing 3.0 country rules (NL, DE, IT, SE, DK, NO, GR, IS)CountryGreeceSeverityError: the invoice is rejectedSyntaxUBLApplies toOnly when the seller (or for some rules the buyer) is in the named country: the rule is triggered by the country code of the party. Dutch rules implement NLCIUS, German rules the XRechnung requirements inside Peppol.

Official rule text

[GR-R-004-1] When Supplier is Greek, there must be one MARK Number

Why this error occurs

This rule only applies when another field has a certain value (for example a payment means code or an invoice type). Your file triggers the condition but does not provide the data that then becomes mandatory, or provides data that is then forbidden.

How to fix it

Either change the triggering value so the condition no longer applies, or add/remove the dependent elements as the rule text describes. Check the condition in the XPath test above to see exactly which value triggers it.

What the validator checks

Checked element (context):

UBL

/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 (XPath):

count(cac:AdditionalDocumentReference[cbc:DocumentDescription = '##M.AR.K##'])=1

Check your invoice

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Same check via API:

curl -F file=@invoice.xml https://einvoicechecker.com/v1/validate

Related rules

GR-R-004-2 When Supplier is Greek, the MARK Number must be a positive integer

Frequently asked questions

What does GR-R-004-1 mean?

GR-R-004-1 is a peppol national rule: When Supplier is Greek, there must be one MARK Number

Will my invoice be rejected because of GR-R-004-1?

Yes. GR-R-004-1 is flagged "fatal"; validators (KoSIT, Peppol access points, the German ZRE/OZG-RE portals, KSeF) reject the invoice until it is fixed.

Which formats does GR-R-004-1 apply to?

Only when the seller (or for some rules the buyer) is in the named country: the rule is triggered by the country code of the party. Dutch rules implement NLCIUS, German rules the XRechnung requirements inside Peppol. Syntax: UBL.

Source: Peppol BIS Billing 3.0.20 national rules (November 2025). Catalogue generated from the official rule sets on 2026-10-15.