You can create a restocking fee item and apply it to credit memos when a
customer returns goods for which they will not receive a full refund.
Go to the Lists menu and click Item List.
Click Item at the bottom of the list and click New.
For Type, select Other Charge.
For Item Name/Number, enter Restocking Fee.
For Amount or %, enter the set price or percentage you typically charge a
customer if they return an item because they decide they no longer want it.
Note that this is a default value that you can change when you create the
customer credit memo.
For Account, select an income account (such as Miscellaneous Revenue) to
associate with restocking fee funds.