The bill approved in Congress to avert the so-called fiscal cliff would bring the first major tax increase on high earners in 20 years.

While leaving income-tax rates in place for most Americans, taxpayers with more than $400,000 in taxable income or couples with $450,000 would see the top marginal tax rate rise to 39.6% in 2013 from 35% in 2012. For income earned below that level, the 2012 rates would be permanently extended.

Taxes...