When does one have to pay back 1 or 2 earned on social security?

You may have to pay back Social Security benefits if you earn more than the annual earnings limit while receiving benefits before reaching full retirement age. For 2023, if you earn over $21,240, your benefits will be reduced by $1 for every $2 you earn above this limit. Once you reach full retirement age, your earnings do not affect your benefits, and any withheld benefits will be recalculated and paid back to you.