26 U.S.C. § 68 - Overall limitation on itemized deductions

(1) 3 percent of the excess of adjusted gross income over the applicable amount, or

(2) 80 percent of the amount of the itemized deductions otherwise allowable for such taxable year.

(1) In general 
For purposes of this section, the term applicable amount means $100,000 ($50,000 in the case of a separate return by a married individual within the meaning of section 7703).

(2) Inflation adjustments 
In the case of any taxable year beginning in a calendar year after 1991, each dollar amount contained in paragraph (1) shall be increased by an amount equal to

(1) the deduction under section 213 (relating to medical, etc. expenses),

(2) any deduction for investment interest (as defined in section 163 (d)), and

(3) the deduction under section 165 (a) for casualty or theft losses described in paragraph (2) or (3) of section 165 (c) or for losses described in section 165 (d).

(1) In general 
In the case of taxable years beginning after December 31, 2005, and before January 1, 2010, the reduction under subsection (a) shall be equal to the applicable fraction of the amount which would (but for this subsection) be the amount of such reduction.

(2) Applicable fraction 
For purposes of paragraph (1), the applicable fraction shall be determined in accordance with the following table: