@DoninGA wrote:
The SS taxable income is from all your W-2's box 3 and any net self-employment income that you reported on a tax return.
Even if your only income is wages from a W-2 job, your social security wages (W-2 box 3) will often be more than your gross wages (box 1) because certain payroll deductions (like 401k contributions) are exempt from income tax but are not exempt from social security tax.
There is also an annual social security maximum wage, which was $132,900 for 2019 (and is inflation-linked). Any year that you earn more than the SS wage base, your SS earnings will be the maximum for that year.
And some earnings are exempt from SS tax, such as certain earnings while a college student or graduate student and during certain Fellowships, so you might have zero SS wages in a year when you were a student or Fellow even though you had taxable income. Some job classifications are entirely exempt from SS tax, depending on your state of residency.
