crediting rates, the interest crediting rate which is treated as in effect and as the projected interest crediting rate shall be a reasonable projection of such variable interest crediting rate, not to exceed 6 percent. . (c) Effective date The amendments made by this section shall apply with respect to years beginning after the date of the enactment of this Act. 402. Aligning use of lookback months to determine interest rates (a) In general The Secretary of the Treasury shall modify Treasury Regulation section 1.417(e)–1(d)(10)(ii) (or any successor provision) to provide that the same rule applicable to modifications of the time for determining the applicable interest rate shall apply to modifications of the time for determining any interest rate used by a plan to the extent that the use of such interest rate is permissible under section 417(e)(3) of the Internal Revenue Code of 1986. Such modified regulations shall require that after any such modification of such time under a plan pursuant to this section, no further modifications of such time are to be permitted for 5 years with respect to such plan without the consent of the Secretary of the Treasury. (b) Effective date The modifications and amendments required under subsection (a) shall be deemed to have been made as of the date of the enactment of this Act, and as of such date all applicable laws shall be applied in all respects as though the actions which the Secretary of the Treasury is required to take under such subsection had been taken. 403. Corrections of mortality tables (a) In general Not later than 6 months after the date of the enactment of this Act, the Secretary of the Treasury shall amend the regulation relating to Mortality Tables for Determining Present Value Under Defined Benefit Pension Plans (82 Fed. Reg. 46388 (October 5, 2017)). Under such amendment— (1) except as provided in paragraphs (2) and (3), the mortality improvement rates for valuation dates occurring during 2018 shall be based on the mortality improvement rates in the