An extension will give you extra time to file your return, but any tax is still due by the original deadline. An extension can help reduce penalties, but any outstanding balance will still be charged a late payment penalty (0.5 percent per month) and interest (right now at 3 percent annually).
Individual taxpayers can file an extension using Form 4868. Extensions can also be filed online, which has the benefit that you’ll receive a confirmation code from the IRS notifying you that your extension was received. Businesses request an extension using Form 7004.
Note well: While an extension gives you extra time to file your return, an extension does not give you extra time to pay your tax.
Payments are still due by April 17, 2018 for the year 2017. But an extension can help reduce your penalties if you cannot afford to pay in full by the deadline.