what is the method for calculating earned income by IRS for people receiving social security

I cannot afford to have any suprises .....

If I am receiving benefits, what is the formula the IRS uses for reporting my monthly income to social security please? They told me I have to report my income to them monthly.

And even if they gave me wrong info... What exactly is the method to calculate earned income because they told me it is not the same way I calculate it for taxes?

Iam so confused and worried.

Thank you.