The IRS has issued the 2009 version of IRS Publication 919, How Do I Adjust My Tax Withholding? as a result of the "Making Work Pay" credit in the American Recovery and Reinvestment Act of 2009 (ARRA).

Employees can use this publication to help them determine if their federal income tax withholding is sufficient, and, if necessary, prepare a new Form W-4 to adjust their withholding. The publication includes worksheets for projecting 2009 tax, withholding, and deductions. For 2009, a new worksheet (Worksheet 12) has been added on the "Making Work Pay" credit.The amount of the "Making Work Pay" credit is $400 (unless the person makes under $6,450; then it’s 6,2% of compensation).  Because the credit is refundable (people can get it even if they owe no tax), most low-income workers will also qualify for the full credit.  The credit is phased out for a married couple filing a joint return whose modified adjusted gross income (AGI) is between $150,000 and $190,000, and for other taxpayers whose modified AGI is between $75,000 and $95,000.

It is a good idea to look at Publication 15T and print out the employee notice (on page 73 of the publication) that you should provide to your employees explaining the changes.  Some employees are beginning to discover after filing their 2008 personal income tax returns that they didn't have enough money withheld from their paychecks.  Employees may really feel the shortfall in 2009 with the changes in the withholding rates.