[IBR-057-OM] - Invoice line period start date (ibt-134) and Invoice line period end date (ibt-135) when provided must belong to the same calendar month.
IBR-057-OMcac:InvoiceLine | cac:CreditNoteLinenot($isSummary) or (substring(cac:InvoicePeriod/cbc:StartDate,1,7) = substring(cac:InvoicePeriod/cbc:EndDate,1,7))