same principal residence In the case of a taxpayer to whom a credit under subsection (a) is allowed by reason of subsection (c)(7), subparagraphs (A), (B), and (C) shall be applied by substituting $6,500 for $8,000 and $3,250 for $4,000 . (2) Limitation based on modified adjusted gross income (A) In general The amount allowable as a credit under subsection (a) (determined without regard to this paragraph) for the taxable year shall be reduced (but not below zero) by the amount which bears the same ratio to the amount which is so allowable as— (i) the excess (if any) of— (I) the taxpayer’s modified adjusted gross income for such taxable year, over (II) $125,000 ($225,000 in the case of a joint return), bears to (ii) $20,000. (B) Modified adjusted gross income For purposes of subparagraph (A), the term modified adjusted gross income means the adjusted gross income of the taxpayer for the taxable year increased by any amount excluded from gross income under section 911, 931, or 933. (3) Limitation based on purchase price No credit shall be allowed under subsection (a) for the purchase of any residence if the purchase price of such residence exceeds $800,000. (4) Age limitation No credit shall be allowed under subsection (a) with respect to the purchase of any residence unless the taxpayer has attained age 18 as of the date of such purchase. In the case of any taxpayer who is married (within the meaning of section 7703), the taxpayer shall be treated as meeting the age requirement of the preceding sentence if the taxpayer or the taxpayer's spouse meets such age requirement. (c) Definitions For purposes of this section— (1) First-time homebuyer The term first-time homebuyer means any individual if such individual (and if married, such individual’s spouse) had no present ownership interest in a principal residence during the 3-year period ending on the date of the purchase of the principal residence to which this section applies. (2) Principal residence The term principal residence has the same meaning as when used in