Here is an article that provides the percentages of social security benefits that are taxable to you:
https://www.ssa.gov/benefits/retirement/planner/taxes.html
Regarding your question about SS tax being taken out of your pay:
Your benefits may increase when you work:
As long as you continue to work, even if you are receiving benefits, you will continue to pay Social Security taxes on your earnings. However, the social security administration will check your record every year to see whether the additional earnings you had will increase your monthly benefit.
Thank you,
John
CPA
