Our high-value merchants use the photo upload add-on for this. See Photo Uploads Add-On / Let customers upload photos for a return for a demo of this feature.
You can require the customer to upload photos of the serial number(s) during the returns process to proceed with the return. Staff can then check the serial numbers on the images in the merchant dashboard.
This process has significant benefits over entering the serial number by hand.
less error-prone than letting customers enter Serial Numbers manually
proof that the customer is actually in possession of the item
better intelligence on the condition of the item
a better experience for the customer
As an alternative, each product in the return has a notes-field attached to it that can be used for Serial Number entry. The description and title of the notes field can be customized to match its purpose.
The following screenshot depicts an exemplary upload request during the return process. Texts can be customized in the Rich Returns dashboard.