To send a receipt to a customer:
If it was paid through Stripe, turn on the email receipts setting directly in Stripe.
To automatically send a receipt to your customers in Stripe:
Log in to your Stripe account.
Select Settings in the left sidebar.
Click Emails.
Toggle on Successful payments.
Click Save to apply.
If it is another payment type - you can send a paid-in-full Invoice, or send a Transaction History Statement from Fieldwork.