When you reach FRA you no longer need to report your earnings to Social Security. 

Find  your full retirement age here.

You do, however, need to report earnings for those months in the calendar year before the month you reach FRA. For example, if you reach FRA in May, you would need to report your earnings for the four earlier months. The law also changed the annual earnings limit for workers who reach FRA during the year. During those months before you reach FRA, your benefits would be reduced $1 for each $3 you earned over the limit which is $33,240 in 2006 and $34,440 in 2007.