Landscape has changed for higher-income individuals

Most individuals will pay federal income taxes for 2015 based on the same federal income tax rate brackets (10%, 15%, 25%, 28%, 33%, and 35%) that applied for 2013. The same goes for the maximum tax rate that generally applies to long-term capital gains and qualifying dividends (for those in the 10% or 15% marginal income tax brackets, a special 0% rate generally applies; for those in the 25%, 28%, 33%, and 35% brackets, a 15% maximum rate will generally apply).

Starting this year, however, a new 39.6% federal income tax rate applies if your taxable income exceeds $400,000 ($450,000 if married filing jointly, $225,000 if married filing separately, $425,000 if filing as head of household). If your income crosses that threshold, you'll also be subject to a new 20% maximum tax rate on long-term capital gains and qualifying dividends.

You could see a difference even if your income doesn't reach that level. That's because, if your adjusted gross income (AGI) is more than $250,000 ($300,000 if married filing jointly, $150,000 if married filing separately, $275,000 if filing as head of household), your personal and dependency exemptions may be phased out this year, and your itemized deductions may be limited.

Two new Medicare taxes need to be accounted for this year as well. If your wages exceed $200,000 this year ($250,000 if married filing jointly or $125,000 if married filing separately), the hospital insurance (HI) portion of the payroll tax--commonly referred to as the Medicare portion--is increased by 0.9%. Also, a new 3.8% Medicare contribution tax now generally applies to some or all of your net investment income if your modified adjusted gross income exceeds those dollar thresholds.