But if you have too much income, you lose out. The credit is reduced at the rate of 2 percent of modified adjusted gross income above $75,000 for singles and $150,000 for couples. (Thus, singles with incomes of $95,000 and couples with incomes of $190,000 get no credit.)
For those who qualify, this credit amounts to a rebate of the 6.2 employee Social Security payroll tax for old age, survivor and disability insurance until the credit reaches the maximum amount. Most workers will start seeing the credit reflected on their take-home pay shortly after April 1 as employers start using new IRS tables calling for lower withholding.
But if you have multiple jobs or anticipate too high an income this year to qualify for the credit, you may have too little money withheld. Again, the solution is to file a new W-4 form appropriate to your situation, and/or adjust your quarterly estimated tax payments.