If you didn't request an extension, the IRS says you should still file your taxes now and pay as much as possible to help reduce penalties and interest. Filed taxes late but expecting a refund ...

An extension request must be filed by the normal April 18 tax deadline. Since it's automatic as soon as you file it, your new deadline will be Oct. 16.

If you miss the deadline and don't request an extension, the Failure to File penalty is 5% of the tax due for any month the return is late, less any tax paid on time and available credits, up to a ...