That's the combined effect of the new law's higher capital-gains rate and limitation on deductions, as well as a new tax this year to help pay for the new health-care law.

WSJ: As Tax Hikes Loomed, Some CEOs Sold Company Stock

If no further action is taken by Congress, the maximum individual income tax bracket would increase to a stated rate of 39.6%, but an effective marginal rate of 40.8% for most high-bracket taxpayers due to a limitation on itemized deductions that would also come back in 2013.

FORBES

While most people are fixated on tax rate increases adding to their income tax bill in 2013 and beyond, very few people are aware that the Pease limitation reinstatement can add to their income tax bills by phasing out some key itemized deductions.

FORBES: Pease Limitation Puts A Lid On Itemized Deductions For Wealthy Folks