In order to receive items you have sold that are being returned you can do one of these things
Go to the Sales section and click on New Return. You will then need to enter the Document Template and the Document Number or the Product and Document Date and you will be guided for the next steps.
You can enter in the search field (top right) the document number your client has bought that product with. For example, if they have bought the item with Ship on Consignment #23 you enter 23 and you will find that Shipment. Clicking on it will allow you to issue a Return of Goods from Client as you would in (1).
3. You can also enter in the search field the product number and you will then be able to find the recent documents that product has been sold with. Having that you can follow the process in (2) to again issue a Return of Goods from Client.
Note: that the same processes can be used either with product codes or serial numbers.