The amount of the credit received must be reported on the employee’s 2009 income tax return filed in 2010. Taxpayers who do not have taxes withheld by an employer during the year can also claim the credit on their 2009 tax return.
It is not necessary to submit a Form W-4 to get the automatic withholding change. However, an employee with multiple jobs or married couples whose combined incomes place them in a higher tax bracket may elect to submit a revised W-4 to ensure enough withholding is held to cover the tax for his or her combined income
The benefit will generally be spread out over the paychecks they receive beginning this spring and continue until the end of the year. Many higher-income taxpayers will see little or no change in their take-home pay. That’s because the Making Work Pay 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 other taxpayers whose modified AGI is between $75,000 and $95,000.
Taxpayers will not get a separate, special check mailed to them from the IRS like last year’s economic stimulus payment.
—http://www.savingtoinvest.com/2009/01/no-second-stimulus-rebate-checks-1000.html