What is in W2 box 3? The max is 137,700.
Yes you numbers are right. Your Net Profit is 3,209.
3,209 x .9235 = 2,963.51
2,963.51 x .029 (Medicare %) = $86 self employment tax
But also you get to deduct $43 (1/2 SE tax) from your total income for your regular income tax. You pay both SE tax and income tax on your Net Profit.
