or after January 1 of the first calendar year that begins after the date of enactment of this Act. 4. Taxes on unearned income (a) Modifications to tax on net investment income (1) In general Section 1411 of the Internal Revenue Code of 1986 is amended by adding at the end the following new subsection: (f) Additional amount for certain high income individuals (1) Inclusion of specified net income (A) In general In the case of any individual whose modified adjusted gross income for the taxable year exceeds the high income threshold amount, subsection (a)(1) shall be applied by substituting the greater of specified net income or net investment income for net investment income in subparagraph (A) thereof. (B) Phase-in of increase The increase in the tax imposed under subsection (a)(1) by reason of the application of subparagraph (A) (determined before application of paragraph (2)) shall not exceed the amount which bears the same ratio to the amount of such increase (determined without regard to this paragraph) as— (i) the excess described in subparagraph (A), bears to (ii) $100,000 ( 1/2 such amount in the case of a married taxpayer (as defined in section 7703) filing a separate return). (2) Additional rate bracket In the case of any individual whose modified adjusted gross income for the taxable year exceeds the high income threshold amount, the amount of tax imposed under subsection (a)(1) shall be increased by an amount equal to 13.6 percent of the lesser of— (A) the greater of the specified net income or net investment income for the taxable year, or (B) the excess (if any) of— (i) the modified adjusted gross income for such taxable year, over (ii) the high income threshold amount. (3) Definitions (A) High income threshold amount For purposes of this subsection, the term high income threshold amount means— (i) except as provided in clause (ii) or (iii), $400,000, (ii) in the case of a taxpayer making a joint return under section 6013 or a surviving spouse (as defined in section 2(a)), $500,000, and (iii) in the