With our previous system RMS, when processing a return, we could select a customer and a date range, and look for transactions from this customer in this date range.

This made the return far less error prone. In general, we have not found returns easy since the move to Citrus Lime (much faster and easier on the old system) and this would be a help -whether it is implemented from the customer purchase history or as an extra condition on a standard return (if a customer is selected, only show transactions for return relating to that customer).