# HAP1650-3a

Source: https://xmlvalid.com/rules/HAP1650-3a

> The invoice number (InvoiceNumber) is empty.

- Level: error
- Rule sets: Facturae validation rules of the Spanish public sector Orden HAP/1650/2015, Facturae 3.2.x description of 6 June 2017
- Context: `/*:Facturae/*:Invoices/*:Invoice`
- Test: `normalize-space(*:InvoiceHeader/*:InvoiceNumber) != ''`

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