Documentation for classifieds purchase

A ward member has asked if there is anything special that needs to be done to document the purchase of an item (e.g., a tent, or some sort of camping gear) from an individual through some sort of platform (e.g., through ksl classifieds or Facebook). Is there specific info that she needs to get from the seller in the form of a receipt, or a form that she should complete? I’m not sure what to tell her that she needs as a receipt is not typical. Before the purchase, she would have approved previously with the bishop.

Even with electronic transactions, there's usually something emailed, or can be printed (perhaps to PDF), or at least a screen shot.

As long as the essential elements of a receipt are provided in writing then there should be no problem. Those essential elements are date of purchase, seller/retailer/vendor name, item(s) purchased, selling price of each item and total amount of purchase (including tax if required). If the seller is not willing to provide a receipt then the buyer can write down the essential elements. While not required, a signature from either the seller or buyer on the document would not hurt.