The deadline to request an extension was April 15. Now your return is just late unless you are in a combat zone or in one of the federally declared disaster areas that have automatic extensions. And an extension does not give you extra time to pay tax due. It only gives you extra time to prepare and file your Form 1040. Get your return filed and pay any tax due as soon as possible to mitigate late filing penalties and interest. If you are getting a refund or do not owe, there is no penalty for missing the deadline.