If you claim your benefit before "full retirement age" but you keep working, your benefit for next year can be reduced by how much you work this year. However, if you are at or older than your full retirement age, then continuing to work will not reduce your benefit.
Separately, if you continue to work after taking your benefit, you might increase your benefit by increasing your credits, but you will not reduce your benefit. Your benefit is based on your average income over the top 35 wage-earning years. If you earn more than the average, it may increase your benefit, but if you earn less than your average, it won't reduce your benefit.
No matter how old you are or whether or not you continue to work, your SS benefit can be taxed if your other income (from working, prizes, pension, etc.) is more than a certain threshold.
