# FX-SCH-A-000213

Source: https://xmlvalid.com/rules/FX-SCH-A-000213

> If Invoice line period (BG-26) is used, the Invoice line period start date (BT-134) or the Invoice line period end date (BT-135) shall be filled, or both.

- Level: error
- Rule sets: Factur-X BASIC rules 1.09
- Context: `//ram:SpecifiedLineTradeSettlement/ram:BillingSpecifiedPeriod`
- Test: `(ram:StartDateTime) or (ram:EndDateTime)`

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