Section 6A. (a) Notwithstanding any general or special law to the contrary, upon the request of the board of selectmen in a town, the city council in a city with a plan E form of government or the mayor in any other city, within any fiscal year, the department of revenue may recalculate the minimum required local contribution for that year. Based on the criteria established in this section, the department of revenue shall recalculate the minimum required local contribution for a municipality's local and regional schools and shall certify the amounts calculated to the department of elementary and secondary education.

(b) A city or town that used qualifying revenue amounts in a fiscal year which are not available for use in the next fiscal year, or that is required to use revenue for extraordinary non-school-related expenses for which it did not have to use revenues in the preceding fiscal year or that has an excessive certified municipal revenue growth factor which is greater than or equal to 1.5 times the state average municipal revenue growth factor may appeal to the department of revenue, not later than October 1, for an adjustment of its minimum required local contribution and net school spending for that fiscal year.

(c) If an appeal is determined to be valid, the department of revenue may reduce proportionately the minimum required local contribution amount based on the amount of shortfall in revenue or based on the amount of increase in extraordinary expenditures in the current fiscal year; provided however, that no adjustment to the minimum required local contribution on account of an extraordinary expense in the budget for the fiscal year in which the waiver is granted, shall affect the calculation of the minimum required local contribution in subsequent fiscal years. Qualifying revenue amounts shall include, but not be limited to, extraordinary amounts of free cash, overlay surplus and other available funds.

(d) If upon submission of adequate documentation, the department of revenue determines that a municipality's appeal regarding an excessive municipal revenue growth factor is valid, the department of revenue shall recalculate the municipal revenue growth factor and the department of elementary and secondary education shall use the revised growth factor to calculate the preliminary local contribution, the minimum required local contribution and any other factor that directly or indirectly uses the municipal revenue growth factor. Any relief granted as a result of an excessive municipal revenue growth factor shall constitute a permanent reduction in the minimum required local contribution.

(e) The board of selectmen in a town, the city council in a city with a plan E form of government, the mayor in any other city or a majority of the member municipalities of a regional school district, which used qualifying revenue amounts in a fiscal year that are not available for use in the next fiscal year, may appeal to the department of revenue, not later than October 1, for an adjustment to its net school spending requirement for that fiscal year. If an appeal is determined to be valid, the department of revenue shall reduce the net school spending requirement based on the amount of the shortfall in revenue and reduce the minimum required local contribution of the member municipalities accordingly. Qualifying revenue amounts shall include, but not be limited to, extraordinary amounts of excess and deficiency, surplus and uncommitted reserves.

(f) If the regional school budget has already been adopted by two-thirds of the member municipalities then, upon a majority vote of the member municipalities, the regional school committee shall adjust the assessments of the member municipalities in accordance with the reduction in minimum required local contributions approved by the department of revenue or the department of elementary and secondary education in accordance with this section.

(g) Notwithstanding clause (14) of section 3 of chapter 214 or any other general or special law to the contrary, the amounts determined under this section shall be the minimum required local contribution described in this chapter. The department of revenue and the department of elementary and secondary education shall notify the house and senate committees on ways and means and the joint committee on education of the amount of any reduction in the minimum required local contribution amount.

(h) If a city or town has an approved budget that exceeds the recalculated minimum required local contribution and net school spending amounts for its local school system or its recalculated minimum required local contribution to its regional school districts as provided in this section, the local appropriating authority shall determine the extent to which the community shall avail itself of any relief authorized by this section.

(i) The amount of financial assistance due from the commonwealth in any fiscal year, under this chapter or any other law, shall not be changed on account of any redetermination of the minimum required local contribution pursuant to this section.

(j) The department of revenue and the department of elementary and secondary education shall issue guidelines to implement their respective duties pursuant to this section.