payroll rates in effect as of the date of the determination. The payroll used in determining the minimum municipal obligation of a pension plan under section 303(c) of the act (53 P. S. § 895.303(c)) shall be based on the payroll to be reported on the Internal Revenue Service Form W-2 and shall be the estimated payroll for the active membership of the pension plan, including projected increases in active membership, for the following plan year. The revised calculation of the minimum municipal obligation, as prescribed under sections 302 and 303 shall be implemented for the minimum municipal obligations developed for the plan years commencing after December 31, 1991. If a municipality fails to adopt a minimum municipal obligation, the minimum municipal obligation shall be calculated using the actual payroll and member contributions for the applicable year and actuarial data extracted from the certified actuarial valuation prepared immediately before the year for which the minimum municipal obligation is to be calculated. The minimum municipal obligation calculated under this subsection shall be used to determine compliance with the actuarial funding standard. References Government finances in the United States