You can make a payment from your bank account directly to the IRS for your individual tax return, an amended tax return, an installment agreement, extensions, estimated tax payments, or payments related to various IRS notices.
Direct Pay is available during the following hours: Monday to Saturday: Midnight to 11:45 p.m. ET and Sunday: 7 a.m. to 11:45 p.m. ET.
You must set your payment up a day before you actually want them to receive it. So if you want the payment to post on the 15th then you must set the payment up the day before (weekends and holidays could affect when you have to set up your payment!
Click here for more information on how to pay the IRS with DirectPay.