Head over to the IRS website for directions. You’ll need to fill out this form, known as Form 4868, and it’s usually due by April 15. If you apply successfully, you’ll get a six month extension on your tax filing deadline.
Remember: Getting an extension doesn't give you more time to pay the taxes you may owe. You'll be charged a late payment penalty if you don't pay your taxes on time.
Special rules may apply (if you’re living outside the country, for example) so be sure to consult the IRS website before filing for an extension.