There are several ways to interpret your question.
- You pay SS and medicaid taxes on "compensation" from working, that's W-2 wages and self-employment. You pay these taxes on your compensation from working no matter how old you are, and no matter if you declare retirement or collect your SS benefit. If you are 90 years old working as a Walmart greeter, you still pay SS and medicaid tax on your wages.
- If you declare retirement and start taking your SS benefit before your "full retirement age" but continue to work (including full time, part time, side gig, etc.) then your employment can reduce your SS benefit, until you reach full retirement age.
- If you retire and social security is your only income, your SS benefit not taxable. However, if you have other income (from work, pension, 401k, IRA, gambling, etc.) then your benefit can be taxable as well. Your benefit is taxable based on your other income and is not affected by your age.
