You need Turbotax Business (download only) to file 1120s. Not TT Home and Business.
You can buy that from Intuit directly at https://turbotax.intuit.com/small-business-taxes/ or from Amazon at http://amzn.to/2DEF1eF ...
If you are asking when to file an 1120 (C-corps) or 1120s (S-corps) you file them by the middle of the third month after their fiscal year ends. If the corporation is on a calendar year, that is March 15. You can get a six-month extension by filing form 7004.