Please refer to IRS Form 2210 Underpayment of Estimated Tax by Individuals, Estates, and Trusts for additional information.
If you owe tax and are filing after the due date of the return, you should send in payment with your return. Your penalty will be based on the amount you owe and the number of days it is late. The number of days late value can only be calculated by the IRS because they must determine the date received. Although you can e-file and request a direct withdrawal date, that may or may not be the actual date the funds are received by the IRS.
The IRS will send you a bill to notify you of the amount of the penalty owed. Any further inquiries regarding your penalty or penalty calculation details should be directed to the IRS at 1-800-829-1040.