May 12 - Employers Social Security, Medicare, and withheld income tax. File form 941 for the first quarter of 2008. This due date applies only if you deposited the tax for the quarter in full and on time. 

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

May 15 - Employers - Nonpayroll withholding. If the monthly deposit rule applies, deposit the tax for payments in April. 

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

June 10 - Employees who work for tips. If you received $20 or more in tips during May, report them to your employer. You can use Form 4070. 

June 16 - Individuals. If you are a U.S. citizen or resident alien living and working (or on military duty) outside the United States and Puerto Rico, file Form 1040 and pay any tax, interest, and penalties due. Otherwise, see April 15. If you want additional time to file your return, file Form 4868 to obtain 4 additional months to file. Then file Form 1040 by October 15.  However, if you are a participant in a combat zone you may be able to further extend the filing deadline. 

Individuals. Make a payment of your 2008 estimated tax if you are not paying your income tax for the year through withholding (or will not pay in enough tax that way). Use Form 1040-ES. This is the second installment date for estimated tax in 2008. 

Corporations. Deposit the second installment of estimated income tax for 2008. A worksheet, Form 1120-W, is available to help you estimate your tax for the year. 

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

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