March 12 - 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 17 - 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 2007 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 2007 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. 

S corporation election - File Form 2553, Election by a Small Business Corporation, to choose to be treated as an S corporation beginning with calendar year 2008. If Form 2553 is filed late, S treatment will begin with calendar year 2009. 

March 31 - Electronic filing of Forms 1098, 1099, and W-2G. File Forms 1098, 1099, or W-2G with the IRS. This due date applies only if you file electronically (not by magnetic media). Otherwise, see February 28.
The due date for giving the recipient these forms will still be January 31.

For information about filing Forms 1098, 1099, or W-2G electronically, see Publication 1220, Specifications for Filing Forms 1098, 1099, 5498 and W-2G Magnetically or Electronically.