`UBL-SR-52`

Document reference shall occur maximum once

Official rule text

[UBL-SR-52]-Document reference shall occur maximum once

Where the rule applies

Rule set	Document type	Severity
XRechnung with the CEN EN 16931 rules (3.0.2) KoSIT, CEN	EN16931 XRechnung (UBL Invoice), EN16931 XRechnung Extension (UBL Invoice), EN16931 XRechnung CVD (UBL Invoice), EN16931 XRechnung (UBL CreditNote), EN16931 XRechnung CVD (UBL CreditNote), EN16931 (UBL Invoice), EN16931 (UBL CreditNote)	fatal
Peppol BIS Billing 3.0 (3.0-2026.5) OpenPeppol	Peppol BIS Billing 3.0 (UBL Invoice), Peppol BIS Billing 3.0 (UBL CreditNote)	fatal
HR-CIUS (eRačun) (1.0.4) Croatian Tax Administration	HR-CIUS (UBL Invoice), HR-CIUS (UBL CreditNote)	fatal

Fatal and error findings make the invoice invalid (valid: false); warnings and information do not.

Technical check

Syntax: UBL · HR-CIUS (eRačun) (1.0.4), Peppol BIS Billing 3.0 (3.0-2026.5), XRechnung with the CEN EN 16931 rules (3.0.2)
Context: cac:InvoiceLine | cac:CreditNoteLine
Test (must be true): count(cac:DocumentReference) <= 1

How the API reports this rule

Every finding of POST /v1/validate carries the rule id, severity, message, location (XPath) and rule set, and links this page (docUrl):

{
  "severity": "fatal",
  "ruleId": "UBL-SR-52",
  "message": "[UBL-SR-52]-Document reference shall occur maximum once",
  "xpath": "/…",
  "source": "schematron:xrechnung@3.0.2",
  "docUrl": "https://einvoice-api.eu/rules/ubl-sr-52.html"
}

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Rule text and severity are taken unchanged from the official rule set; this page is generated from the API's configuration. Not legal advice.