Also called: SE tax, SECA, FICA
The self-employed pay both halves of Social Security and Medicare tax: 12.4% plus 2.9% on 92.35% of net earnings. Half of the tax is deductible in arriving at AGI.
The 12.4% Social Security part stops at the annual wage base, which is shared with any W-2 wages. The 2.9% Medicare part has no cap. Employees pay half of each rate through FICA withholding and the employer pays the other half.