BT-1: Invoice Number
Unique identifier of the invoice assigned by the seller.
Technical Specification
Mandatory (1..1) in every e-invoice
Semantic data format according to European Standard EN 16931-1
What does BT-1 mean?
The invoice number (BT-1) uniquely identifies the invoice document throughout its retention period. In according with tax regulations, every invoice must bear a sequential, unique number. In EN 16931, XRechnung, and ZUGFeRD, BT-1 is a strict root-level mandatory field.
Practice Context: B2B vs. B2G (Public Procurement)
Applies equally to B2B and B2G invoices. Must be unique and persistent.
XML Syntax & Code Example
<cbc:ID>RE-2026-0842</cbc:ID>Business Rules & Schematron Checks
An invoice shall have an Invoice number (BT-1).
Check BT-1 in your invoice
Use the XML paths above to locate BT-1. A snippet illustrates this field; it is not a complete invoice. After correcting a value in the source application, export and check the entire file again.
Official specifications and rule sets
Requirements depend on the invoice profile and version. Consult the matching specification for mandatory fields, code lists and rules; Peppol-specific requirements do not automatically apply to every ZUGFeRD invoice.
Related Business Terms (BTs)
Create compliant E-Invoices easily
Create XRechnung and ZUGFeRD invoices in Billance and check the exported file locally. Use this guide to understand BT-1 and review your invoice details before sending.