March 11 

Employees who work for tips - If you received $20 or more in tips during February, report them to your employer. You can use Form 4070.

March 15

Employers - Nonpayroll withholding. If the monthly deposit rule applies, deposit the tax for payments in February.

Employers - Social Security, Medicare, and withheld income tax. If the monthly deposit rule applies, deposit the tax for payments in February.

Corporations - File a 2012 calendar year income tax return (Form 1120 or 1120-A) and pay any tax due. If you want an automatic 6-month extension of time to file the return, file Form 7004 and deposit what you estimate you owe.

S Corporations - File a 2012 calendar year income tax return (Form 1120S) and pay any tax due. Provide each shareholder with a copy of Schedule K-1 (Form 1120S), Shareholder's Share of Income, Credits, Deductions, etc., or a substitute Schedule K-1. If you want an automatic 6-month extension of time to file the return, file Form 7004 and deposit what you estimate you owe.

Electing large partnerships - Provide each partner with a copy of Schedule K-1 (Form 1065-B), Partner's Share of Income (Loss) From an Electing Large Partnership. This due date is effective for the first March 15 following the close of the partnership's tax year. The due date of March 15 applies even if the partnership requests an extension of time to file the Form 1065-B by filing Form 8736 or Form 8800.