Issue: Freight Condition amount is not showing as negative during Return PO creation.

Reason and Prerequisites:
The processing was intentionally converted. It is assumed that freight costs are also incurred for returns and are not refunded i.e. shipping cost is needed to send the stock back to the vendor which will be paid by the Vendor. So, again charging of Freight is not required.
Furthermore, negative delivery costs are not yet supported.

Solution:
If delivery costs are not incurred, you should delete them from the returns order item. If the supplier of goods refunds the freight costs for a possible underlying delivery, you can also enter this as a normal surcharge (for returns, this counts as a discount).

You can refer SAP Note – 210027

Best Regards,

Ganesh Padala