Use Form 8960 Net Investment Income Tax—Individuals, Estates, and Trusts to figure the amount of your Net Investment Income Tax (NIIT).

Per IRS Instructions for Form 8960, on page 1:

Who Must File

Attach Form 8960 to your return if your modified adjusted gross income (MAGI) is greater than the applicable threshold amount.

Application to Individuals

U.S. citizens and residents. Individuals who have for the tax year (a) MAGI that’s over an applicable threshold amount, and (b) net investment income, must pay 3.8% of the smaller of (a) or (b) as their NIIT.

The applicable threshold amount is based on your filing status.

• Married Filing Jointly or Qualifying Widow(er) is $250,000.
• Married Filing Separately is $125,000.
• Single or Head of Household is $200,000.

To make entries for Form 8960 in TaxAct:

1. From within your TaxAct return (Online or Desktop), click Federal. On smaller devices, click in the upper left-hand corner, then click Federal.
2. Click Taxes in the Federal Quick Q&A Topics menu to expand, then click Net investment income tax (Form 8960).
3. The program will proceed with the interview questions for you to enter or review the appropriate information.

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.