 Higher income taxpayers, as well as taxpayers with sources of income that are defined as net investment income in the statute, pay an additional 3.8% tax to offset the costs of the Affordable Care Act.This tax first took effect in 2013.At the time, "higher income taxpayers" were defined as taxpayers with a modified adjusted gross income of $250,000 for married couples filing jointly, $125,000 for married couples filing separately, and $200,000 for individuals or heads of household.