How far in advance should I make a payment?
You should make payments on Pay.gov no later than 7:55 PM US Eastern Time on the business (banking) day before the due date. Business days are Monday through Friday, excluding US holidays. Holidays can affect processing times, so you may want to make payments sooner to avoid being late.
For example, if your payment is due on a Monday, Pay.gov recommends that you make your payment before 7:55 PM the previous Friday.