After you file

It will get debited from your account since that is what you choose.  When you choose to set up a payment plan the program automatically prints a payment voucher in case you decided you want to send in money to reduce your taxes owed.  A penalty & interest incur until the full taxes owed is paid in full so the more you can pay upfront, the less penalty & interest you will incur.  You do not have to send in a payment.