I think the standard things that customers look for on receipts are: the invoice number the payment was applied to (or multiple invoice numbers), if the payment short-paid an invoice, how much is left outstanding on that invoice (which would be self explanatory if it listed the original invoice amount and the payment amount), date of the invoice the payment was applied to, payment method (whether it was cheque or credit card), and if there could be a PDF version attached to the receipt email that would be great, too. I've had a few customers ask for print-friendly copies of the receipt before.
... View more