If you enable auto-reminders on an invoice, your customer will receive three emails: the first one 7 days before the invoice is due, then an email on the due date, and one again 7 days later. 

All reminders are sent between 8:00 and 8:30 a.m. EST.

Note: If your original payment request is sent to the customer within 24 hours of a scheduled reminder, Fincent skips the reminder so they don’t receive the same message twice. However, Fincent will continue to send auto-reminders (and you can see when the next reminder is scheduled) when resending a payment request. 

Note: You must be on Fincent's Starting, Growing, or Thriving plan to request payments and set reminders.