After an invoice is approved, OTM creates a Voucher record for it. Voucher Allocation distributes the total freight cost across the Order Releases on the shipment — proportionally by weight or volume — so each PO or Order Release line carries its share of the freight charge.

Voucher record after invoice approval:

OTM automatically creates the voucher once the invoice is approved:

At this point the ALLOCATION_VOUCHER status on the voucher is NOT ALLOCATED: