Why is interest income taxed twice? First it's added to taxable income (line 2b) and secondly, tax is calculated on Form 8960 ('Net investment income tax') and added in

[psgodley]

My interest income was added to taxable income, but also had tax calculated separately on Form 8960 that was added to the total tax. This looks like the interest income gets taxed twice.

[AnthonyC · Accepted solution]

Yes, interest income can be included in both calculations.  It is included in your overall taxable income calculations.  And, Form 8960 applies a surcharge tax of 3.8% when you have certain net investment income and your modified AGI exceeds certain statutory thresholds. 

You can read more about this tax and its history at the links below -

https://www.irs.gov/individuals/net-investment-income-tax

https://www.irs.gov/newsroom/questions-and-answers-on-the-net-investment-income-tax