Refund Shipping on RMA

To refund shipping charges when generating an RMA, create the RMA as you normally would do via Income -> Orders -> Fulfillment Order -> Process RMAs. Then do the following:

1. Create an RMA Misc Credit type for refunded shipping charges by going to Admin -> Orders -> RMA Setup. Click the Add button in the section under RMA Misc Credits. Set the RMA Credit Description to Shipping Charge Refund or similar. Select if tax should be calculated for the refunded amount, and set a GL account for the shipping charge credit entry (should be the same as Admin -> Billing -> General Setup -> Shipping Liability).
2. Bring up the RMA you wish to add a shipping refund to (Income -> Orders -> Fulfillment Order -> Process RMAs) and click the link Receive Items On This RMA. 
3. In the bottom section you can enter text for Description Misc Credit. This description will appear on the invoice. Select Shipping Charge Refund (or the title you provided) for Credit Class. Enter in the Credit Amount for the amount of shipping to refund (enter as a positive value).

Another option to add the shipping credit is to edit the credit invoice after the RMA has processed.

1. Locate the credit invoice by going to Income -> Invoices. Click the invoice number to view the invoice.
2. Click the Edit button at the top of the page.
3. If you are editing with the POS view (Tools -> Add-Ons -> Edit Invoices on POS), add a negative amount for the shipping refund by clicking the amount next to Shipping in the subtotal area at the bottom of the page..
4. If you are editing the invoice with the non-POS method, click Unpost first, then add a negative amount for the shipping credit in the Shipping box at the bottom of the page. Click Post when done.