If you owe the IRS, you must pay your tax in full by April 15th. If you do not pay your tax in full, the IRS will calculate penalties and interest on your outstanding balance. The penalty for not filing is 5% per month up to a maximum penalty of 25% of the balance due. By contrast, the failure to pay penalty is 0.5% per month, plus interest. The bottom line? If you think you owe, file an extension as a way to avoid the late filing penalty.
Form 4868.....6 month extension
Turbo Tax, TaxAct and H&R Block On-line have methods for filing extension