Today, March 17, 2014 is the deadline for calendar year corporation returns. File today or pay a penalty and interest on any tax due. There are minimum penalties even if the corporation does not owe any tax. Your corporation can get an automatic extension by filing Form 7004 (PDF) with IRS today. You can file the extension form electronically, by mailing via the US Post Office (certified or registered mail highly recommended), or using one of the IRS approved private delivery services.
Generally, you must use a tax software to file the extension form electronically with IRS. Most tax professionals who prepare corporate returns should be able to file the extension electronically.
Extension filing requirements vary by state. Some accept a copy of the Form 7004 mailed with the actual return. Most require the corporation to request an extension on a state specific form. NC requires corporations to use Form CD-419 to request an extension and for payment of any tax due. The NC calendar year corporate returns are not due until April 15, 2014 so you do not have to file the NC extension today. Other states have different deadlines though the majority use the IRS due date. You can find the CD-419 on this page. You can file electronically for free but there is a convenience fee if you use a credit or debit card. NC does not charge for a bank draft. You can also complete a personalized extension form, print it and then mail it via the U.S. Post Office.
The U.S. Post Office lists their hours on their website but you need to remember that IRS and the states are highly unlikely to excuse you if the USPS hours on the website are wrong.