Corporations: File Form 1120 for 2012 calendar year and pay any tax due. For automatic 6-month extension, file Form 7004 and deposit estimated tax.
S Corporations: File Form 1120S for 2012 calendar year and pay any tax due. Furnish a copy of Schedule K-1 to each shareholder. File Form 2553 to elect S Corporation status beginning with calendar year 2013.
Employers: Deposit payroll tax for February if the monthly deposit rule applies.
Note: These tax due dates are based on calendar year taxpayers. If you are a fiscal year taxpayer, you should calculate your quarterly due dates based on your fiscal year end date. Estimated tax payment due dates are the 15th day of the 4th, 6th, 9th, and 12th months of the corporate tax year.