High-income earners should start planning for the 3.8% tax on investment income that will go into effect Jan. 1 as part of the 2010 Affordable Care Act, advisers say. "High earners don't understand the impact. I have one client, a very high net worth individual with a lot of investment interest, who may owe $1.3 million more," said Joseph Perry, partner-in-charge of tax and services for Marcum.