Select Shipping Carrier and Shipping Method with Handle Charge enabled.
Notice that the Handling Cost field is not Editable to manually enter an amount.
- Click the Calculator button beside the Shipping Cost Field
- Click Calculate beside the Shipping Cost in the header of the Sales Order
- The Handling Cost field now becomes editable even if the shipping cost calculated is 0.00.
- Manually enter or change the value in this field
- Save the Sales Order