There are several possibilities depending on what you want to do.

There is 3 options described below.

Option 1 :  The customer doesn’t want the product anymore. You want to receive this item and credit it.

You need to create a shipment, but with a negative quantity. This way, instead of shipping a product to a customer, you will be receiving the product from the customer.
Make sure that the “Create Invoice” option is selected on the Commit button. The credit will be created automatically.

At the same time, the product will be available to resell to someone else, so no need to do anything in your inventory about this item.