If you cannot file your return by the due date, you can request an extension of time to file. But it’s important to keep in mind that filing for an extension of time to file does NOT give you an extension of time to pay your tax bill. If you do not pay by the due date, you will owe interest on any past-due tax, and in addition you may be subject to a late-payment penalty.
To receive an automatic six-month extension of time to file your tax return, file Form 4868 by the due date. It’s a good idea to include in the payment you send with your extension request any additional amounts you might owe.
The rules vary for state filing extensions. Check your state’s requirements.