(4) Denial of deductions if converted to rental housing If, during the 5-year period beginning on the date of the qualified completion event described in subsection (a), an individual who owns a residence fails to use such residence as such individual’s principal residence for any period of time, no deduction shall be allowed for expenses paid or incurred by such individual with respect to renting, during such period of time, such residence. (5) Waiver The neighborhood homes credit agency may waive the repayment required under paragraph (1) in the case of homeowner experiencing a hardship. (k) Inflation adjustment (1) In general In the case of a calendar year after 2020, the dollar amounts in this section shall be increased by an amount equal to— (A) such dollar amount, multiplied by (B) the cost-of-living adjustment determined under section 1(f)(3) for such calendar year by substituting calendar year 2019 for calendar year 2016 in subparagraph (A)(ii) thereof. (2) Rounding (A) Substantial rehabilitation In the case of the dollar amount in subsection (f)(4), any increase under the preceding sentence which is not a multiple of $1,000 shall be rounded to the nearest multiple of $1,000. (B) In the case of the dollar amount in subsection (g)(1)(A)(i), any increase under the preceding sentence which is not a multiple of $0.01 shall be rounded to the nearest multiple of $0.01. (C) In the case of the dollar amount in subsection (g)(1)(A)(ii), any increase under the preceding sentence which is not a multiple of $100,000 shall be rounded to the nearest multiple of $100,000. . (b) Current year business credit calculation Section 38(b) (of the Internal Revenue Code of 1986) is amended by redesignating paragraphs (6) through (37) as paragraphs (7) through (38), respectively, and by inserting after paragraph (5) the following new paragraph: (6) the neighborhood homes credit determined under section 42A(a), . (c) Limitation on carryback Section 39 of the Internal Revenue Code of 1986 is amended by adding at the end the