You can add a transporter and related contract number to a relation. Added transporter and contract will be displayed in the transport contract field drop-down of the transport order. These added transport contract details are displayed in the order document.
Invoices are displayed on the export screen in a particular month. The month of the invoice is taken from the invoice date and not from another date, such as the due date.
The invoice date is therefore leading in terms of month for export periods. For example: Invoice date 22-05-2022 and due date 15-06-2022. This invoice will appear in the export under the month May.