I need to know how to request extension and file an S-corporation extension — Do I need to file Form 7004?
You can extend filing Form 1120S when you file Form 7004. Enter Code 25 in the box on Form 7004, Line 1. You get an automatic five-month extension to file Form 1120S.
Even if you file an extension, you must still pay the tax you owe by April 15, 2019.
After you file extension by submitting Forms 1040 and 1120S, you’ll receive a refund for any tax you overpaid. If you underpaid, then the amount you still owe will be subject to interest and penalties.