; and (B) the number of the participant’s years of credited service. For each calendar year after the first full calendar year following the date of the enactment of the Emergency Pension Plan Relief Act, the accrual rates in subparagraph (A) shall increase by the national average wage index (as defined in section 209(k)(1) of the Social Security Act). For purposes of this subsection, the rates applicable for determining the guaranteed benefits of the participants of any plan shall be the rates in effect for the calendar year in which the plan becomes insolvent under section 4245 or the calendar year in which the plan is terminated, if earlier. . II Relief for Single Employer Pension Plans 201. Extended amortization for single employer plans (a) 15-year amortization under the Internal Revenue Code of 1986 Section 430(c) of the Internal Revenue Code of 1986 is amended by adding at the end the following new paragraph: (8) 15-year amortization With respect to plan years beginning after December 31, 2019— (A) the shortfall amortization bases for all plan years preceding the first plan year beginning after December 31, 2019 (and all shortfall amortization installments determined with respect to such bases) shall be reduced to zero, and (B) subparagraphs (A) and (B) of paragraph (2) shall each be applied by substituting 15-plan-year period for 7-plan-year period . . (b) 15-year amortization under the Employee Retirement Income Security Act of 1974 Section 303(c) of the Employee Retirement Income Security Act of 1974 ( 29 U.S.C. 1083(c) ) is amended by adding at the end the following new paragraph: (8) 15-year amortization With respect to plan years beginning after December 31, 2019— (A) the shortfall amortization bases for all plan years preceding the first plan year beginning after December 31, 2019 (and all shortfall amortization installments determined with respect to such bases) shall be reduced to zero, and (B) subparagraphs (A) and (B) of paragraph (2) shall each be applied by substituting 15-plan-year period for