[ibr-co-19]-If Invoicing period (ibg-14) is used, the Invoicing period start date (ibt-073) or the Invoicing period end date (ibt-074) MUST be filled, or both.
ibr-co-19
cac:InvoicePeriod
exists(cbc:StartDate) or exists(cbc:EndDate) or (exists(cbc:DescriptionCode) and not(exists(cbc:StartDate)) and not(exists(cbc:EndDate)))