User Activity

What is the process for cleaning up small balances under say 2 dollars? I've got a lot of people who just paid the incorrect tax amount and their balance is like 26 cents.
Is there a way to set up automated text/email reminders for customers who haven't paid their invoice after x amount of days?
I'm trying to bypass an export of a $0 invoice to QB but the button to do so has disappeared. Help?