BR-55
Each Preceding Invoice reference (BG-3) shall contain a Preceding Invoice reference (BT-25).
What the rule checks
As the rule set's publisher wrote it. The rule runs on every element the context matches, and fails where the test is false; the validator reports the line of that element.
cac:BillingReference
exists(cac:InvoiceDocumentReference/cbc:ID)
Checked with EN 16931 Invoice (UBL), EN 16931 Credit Note (UBL), Croatia eRačun Invoice (UBL), Croatia eRačun Credit Note (UBL)
/rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeSettlement/ram:InvoiceReferencedDocument
normalize-space(ram:IssuerAssignedID) != ''
Checked with EN 16931 Invoice (CII)
(/ubl:Invoice | /cn:CreditNote)/cac:BillingReference
exists(cac:InvoiceDocumentReference/cbc:ID)
Checked with France EXTENDED-CTC-FR (UBL)
/rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeSettlement/ram:InvoiceReferencedDocument
(ram:IssuerAssignedID!='')
Checked with France Factur-X BASIC WL, Factur-X / ZUGFeRD BASIC WL