It's possible you are being subject to the Net Investment Income Tax of 3.8%.
The income and gains from investments you hold will be taxed an additional amount if your Modified Adjusted Gross Income meets or exceeds the amount for the filing status below.
- Married filing jointly - $250,000
- Married filing separately - $125,000
- Single - $200,000
- Head of household (with qualifying person) - $200,000
- Qualifying widow(er) with dependent child - $250,000
Form 8960 (Net Investment Income Tax – Individuals, Estates, and Trusts) is used for the 3.8% surtax on investment income for the Affordable Care Act.