Message

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.

Context
cac:InvoiceLine/cac:InvoicePeriod | cac:CreditNoteLine/cac:InvoicePeriod
Test
exists(cbc:StartDate) or exists(cbc:EndDate)
Usage
/ ubl:Invoice / cac:InvoiceLine / cac:InvoicePeriod / cbc:StartDate
/ ubl:Invoice / cac:InvoiceLine / cac:InvoicePeriod / cbc:EndDate
/ ubl:CreditNote / cac:CreditNoteLine / cac:InvoicePeriod / cbc:StartDate
/ ubl:CreditNote / cac:CreditNoteLine / cac:InvoicePeriod / cbc:EndDate