BR-02: Invoice number (BT-1) is missing – e-invoice error explained

StandardEN 16931-1 (European e-invoicing semantic model)SeverityError: the invoice is rejectedSyntaxUBL, CIIBusiness terms

BT-1 Invoice number

Applies toEvery EN 16931 invoice: XRechnung, ZUGFeRD 2.x / Factur-X (profiles EN 16931, EXTENDED, XRECHNUNG), Peppol BIS Billing 3.0, and national CIUS such as the Dutch NLCIUS or the Italian/Spanish profiles.

Official rule text

[BR-02] An Invoice shall have an Invoice number (BT-1).

Why this error occurs

Every invoice needs a unique invoice number; the rule checks that cbc:ID (UBL) or rsm:ExchangedDocument/ram:ID (CII) is present and not blank. The number is required by VAT law in every EU member state and is the key the buyer uses for matching, payment and dispute. It is typically missing when a draft document is exported before numbering, or the ERP mapping points the number to a different field such as cbc:UUID.

How to fix it

In UBL set cbc:ID directly under ubl:Invoice or cn:CreditNote, after cbc:ProfileID. In CII set rsm:ExchangedDocument/ram:ID. Use the invoice number exactly as printed on the invoice, e.g. 2026-00123 or RE-4711. Leading and trailing spaces are ignored by the check but may upset the receiver, so trim them; do not confuse the invoice number with the order number (BT-13) or the UUID.

Example (valid)

<cbc:ID>RE-2026-00123</cbc:ID>
<cbc:IssueDate>2026-10-14</cbc:IssueDate>

What the validator checks

Checked element (context):

UBL

/ubl:Invoice | /cn:CreditNote

Test (XPath):

normalize-space(cbc:ID) != ''

CII

/rsm:CrossIndustryInvoice

Test (XPath):

normalize-space(rsm:ExchangedDocument/ram:ID) != ''

Check your invoice

Drop your XML or PDF on the validator and every failed rule is linked to its page here. Free, no account, the file is not stored.

Check your invoice →

Same check via API:

curl -F file=@invoice.xml https://einvoicechecker.com/v1/validate

Related rules

BR-01 Specification identifier (BT-24) is missing
BR-03 Invoice issue date (BT-2) is missing
BR-04 Invoice type code (BT-3) is missing
BR-05 Invoice currency code (BT-5) is missing
BR-06 Seller name (BT-27) is missing
BR-07 Buyer name (BT-44) is missing
BR-08 Seller postal address is missing
BR-09 Seller country code (BT-40) is missing

Frequently asked questions

What does BR-02 mean?

BR-02 is a en 16931 core rule: An Invoice shall have an Invoice number (BT-1).

Will my invoice be rejected because of BR-02?

Yes. BR-02 is flagged "fatal"; validators (KoSIT, Peppol access points, the German ZRE/OZG-RE portals) reject the invoice until it is fixed.

Which formats does BR-02 apply to?

Every EN 16931 invoice: XRechnung, ZUGFeRD 2.x / Factur-X (profiles EN 16931, EXTENDED, XRECHNUNG), Peppol BIS Billing 3.0, and national CIUS such as the Dutch NLCIUS or the Italian/Spanish profiles. Syntax: UBL and CII.

Source: EN 16931-1:2017 schematron (CEN TC434, via Peppol BIS 3.0.20). Catalogue generated from the official schematron on 2026-10-14.