Hi _ (add the client’s first and last name),
Hope you’re doing well. I just wanted to remind you that the invoice #_ (add invoice number) with the total of _ (add currency and amount due) I’ve sent you on _ (add month and date) is due one week from now.
Although I’m sure you’re busy, I’d greatly appreciate it if you were to go over the invoice and payment details for the services rendered. Please contact me if you have any questions.
_ (add your first and last name)