# FX-SCH-A-000011

Source: https://xmlvalid.com/rules/FX-SCH-A-000011

> An Invoice shall have an Invoice number (BT-1).

- Level: error
- Rule sets: Factur-X MINIMUM rules 1.09, Factur-X BASIC rules 1.09
- Context: `/rsm:CrossIndustryInvoice`
- Test: `(rsm:ExchangedDocument/ram:ID !='')`

Validate a document against these rules: https://xmlvalid.com/validate