Call the IRS at 800-829-1040 to determine if your request for an extension was approved. The customer service representative will be able to advise you if the extension was received and approved. If approved, the extension you get by filing form 4868 will afford you an extension of time to file until October 15.
Submit your extension electronically with your return before the April 15th deadline. Most online tax preparation software companies such as TurboTax and TaxCut allow you to file the electronic version of Form 4868 with your e-filed return. This way, once you receive the email confirmation from the IRS confirming receipt of your return, you will also be able to confirm receipt of the extension. You should receive an email confirmation within 72 hours of your return submission.
Call the IRS International Tax Office at 215-516-2000 if you are out of the country and filed form 2350, Extension of Time to File U.S. Income Tax Return, instead of form 4868. You would only use form 2350 if you submitted form 2555 to claim foreign earned income.