Glossary Term
BT-31

BT-31 Seller VAT Identifier

BT-31 is the seller's VAT registration number, required when the invoice includes VAT and essential for EU intra-community transactions.

Quick Facts

Parent
BG-4 Seller
Condition
Required when VAT is charged
Data type
Identifier
Cardinality
0..1

Definition

What is BT-31?

BT-31 (Seller VAT identifier) contains the seller's VAT (Value Added Tax) registration number. It's conditionally mandatory — required whenever the invoice includes VAT or involves cross-border EU transactions.

Requirements

  • Cardinality: 0..1

  • Data type: Identifier

  • Conditionally mandatory: required when VAT is charged

  • Must follow the country-specific VAT number format

    • VAT Number Formats by Country

    Country Format Example
    --------------------------
    Germany DE + 9 digits DE123456789
    Netherlands NL + 9 digits + B + 2 digits NL123456789B01
    Belgium BE + 10 digits BE0123456789
    France FR + 2 chars + 9 digits FR12345678901
    Italy IT + 11 digits IT12345678901
    Spain ES + 1 letter + 7 digits + 1 char ESB12345678

    In UBL XML


      DE123456789
      
        VAT

    In CII XML


      DE123456789

    When Is It Required?

  • Invoice includes VAT at any rate other than 0%

  • Intra-community supply (reverse charge)

  • Peppol BIS: either BT-31 or BT-32 (seller tax registration) must be present

  • XRechnung: required for all VAT-registered sellers

    • Common Errors

  • Missing when VAT is charged — BR-CO-09 requires BT-31 when tax is present

  • Wrong country prefix — VAT number must start with the correct country code

  • Invalid format — each country has specific length and character rules

  • Missing TaxScheme — the VAT identifier must be nested under a TaxScheme element with ID "VAT"

    • XML Examples

    UBL (Peppol, XRechnung)

    <cbc:CompanyID>DE123456789</cbc:CompanyID>

    CII (ZUGFeRD, Factur-X)

    <ram:ID schemeID="VA">DE123456789</ram:ID>