# DE-R-022

Source: https://xmlvalid.com/rules/DE-R-022

> If both supplier and customer are located in Germany, attached documents provided with an invoice in "ADDITIONAL SUPPORTING DOCUMENTS" (BG-24) shall have a unique filename (non case-sensitive) within the element ″Attached document″ (BT-125).

- Level: error
- Rule sets: Peppol BIS Billing 3.0 rules 3.0.21
- Context: `(/ubl-invoice:Invoice | /ubl-creditnote:CreditNote)[$supplierCountryIsDE and $customerCountryIsDE]`
- Test: `count(cac:AdditionalDocumentReference) = count(cac:AdditionalDocumentReference[not(./cac:Attachment/cbc:EmbeddedDocumentBinaryObject/@filename = preceding-sibling::cac:AdditionalDocumentReference/cac:Attachment/cbc:EmbeddedDocumentBinaryObject/@filename)])`

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