Data Model
Invoice Number (BT-1)
Definition
The invoice number (BT-1) is a unique alphanumeric identifier assigned by the seller to an invoice. It is a mandatory field under EN 16931 and must be unique within the seller's invoicing period. The invoice number is tax-relevant (§ 14 para. 4 UStG) and is used for referencing on payment documents and in communication with the buyer.
Switch to German:Rechnungsnummer (BT-1) (DE)
Related terms
Business Term (BT)A Business Term (BT) is a single, semantically defined data element of the European standard EN 16931. Each Business Term has a unique number (e.g., BT-1 for the invoice number, BT-9 for the payment due date), a name, a definition, and cardinality rules. Business Terms are syntax-independent and are mapped to different XML elements in UBL and CII.EN 16931EN 16931 is the European standard that defines the semantic data model of a core invoice. It specifies the mandatory and optional fields (Business Terms), their meaning, and the validation rules that apply to all conforming electronic invoices in the EU. Nationally implemented standards such as XRechnung, ZUGFeRD (EN 16931 profile), and Factur-X must comply with this standard.Credit Note / Corrected InvoiceA credit note or corrected invoice is issued when an original invoice was erroneous or a supply is reversed. In EN 16931, a credit note is identified with invoice type code 381 and a corrected invoice with code 384. The corrective invoice typically contains the original invoice number as a reference (BT-25) and must include all mandatory fields just like a regular invoice.