BR-1
Invoice Number Missing (BT-1)
What This Error Means
Every EN 16931 invoice must carry a unique invoice identifier (BT-1) in cbc:ID. This is the invoice number as it appears on the paper equivalent. It must be unique within the seller's context and may not be empty or whitespace-only.
Why this happens
BR-1 fires when the invoice has no invoice number (BT-1, cbc:ID) or the element is empty/whitespace. This is a core EN 16931 mandatory field. The cause is almost always a generation bug: the numbering sequence was not assigned before export, a template emitted an empty cbc:ID, or the number was written into the wrong element (e.g. cbc:UUID or a custom reference instead of cbc:ID). Because the invoice number is also a § 14 UStG requirement, a missing value is both a validation and a tax-compliance problem.
How to Fix It
Populate cbc:ID with your invoice number. Ensure it is unique and matches your internal numbering system. Sequential gaps are allowed but duplicates are not.
Step-by-step
1) Populate cbc:ID directly under the Invoice root with your invoice number, e.g. RE-2024-00123. 2) Ensure the value is non-empty and not just spaces. 3) The number must be unique within your invoicing context; gaps in the sequence are allowed but duplicates are not. 4) Do not confuse cbc:ID (BT-1, the human invoice number) with cbc:UUID or with order references. 5) Re-validate. If the field is now present but the receiver still complains about duplicates, your numbering logic is reusing values across documents.
<cbc:ID>RE-2024-00123</cbc:ID>
Fix Automatically
Upload your invoice to our Smart Repair engine. It will detect and fix BR-1 errors automatically with a GoBD audit trail.
Open Smart RepairFrequently asked questions
Can the invoice number contain letters?
Yes. BT-1 is alphanumeric, so values like RE-2024-00123 are valid. It only needs to be present, non-empty and unique within your invoicing context.
Are gaps in the numbering allowed?
Yes, sequential gaps are permitted for EN 16931 validation. What is not allowed is duplicate invoice numbers, which can cause processing or audit issues.
Related Errors
Other commonly encountered validation errors