Hi pippypip
Thank you so much for your post and I am sorry to hear that you were having problems about sending receipts to your costumers. I really appreciate your patience and understanding about this issue and I do apologize for the delayed response. Currently, when your customer makes a payment, you can provide them a copy of the invoice (showing the payment) as a receipt. Our Help Article, Emailing and Printing invoices, has detailed information to assist with this. Having the payment receipt only to forward to customers is a great idea. This is duly noted and we really appreciate and valued your feedback/suggestions. We will relay this to the relevant team.
I would also recommend to post this in our Product Board Ideas for consideration by our developers and for others to vote on this feature.
Feel free to post again, we're happy to help.
Regards,
Earl