There are several choices when paying any taxes owed on your return(s).
For amounts owed to the IRS, Electronic Funds Withdrawal (EFW) is free and allows you to decide when the tax payment is scheduled to be withdrawn from your bank account. Electronic funds withdrawal is available only to those who e-file. Individuals may e-file early and, at the same time, schedule the electronic funds withdrawal as late as April 18, 2016. For returns filed after the filing deadline, the payment is effective on the filing date.
Others options for amounts due to the IRS are: