[CubicleGuy]

Regarding your SS, you need to send back every dollar you make beyond what you paid in, plus interest. Anything after that is hypocracy money.

Who gets to decide on the interest rate?

[VA Advogado]

I think it would be fair to use the Social Security administration's own published interested rate figure they use for disputed payments. Otherwise, the federal courts have their own rate they use for judgments. Finally, there is the refund interest rate for the IRS.