The Social Security Administration has made changes to the retirement earnings test for 2013.  This test only applies to people who have taken early retirement and are under their full retirement age.  One out of two exempt amounts applies depending upon the year you reach your full retirement age.
         
For people younger than the full retirement age of 66 in 2013, the annual exempt amount is $15,120.  That means that for $2 earned over $15,120, Social Security will deduct $1 from your benefit amount.

For people who reach the full retirement age of 66 in 2013, the annual exempt amount is $40,080.  That means that for every $3 earned over $40,080, Social Security will deduct $1 from your benefit amount.

There is no limit on earnings for individuals who reached full retirement age before 2013.  These retirees will not have any benefits withheld regardless of how much money they earn.