244.60. The by-law must(1) define the meaning of non-residential premises, vacancy of a unit of assessment or of premises, average percentage of unoccupancy of a unit and reference period;
(2) prescribe the rules for calculating the abatement;
(3) prescribe the terms and conditions according to which an abatement is granted as well as the rules which apply where a debtor acquires or loses the right to an abatement during a fiscal year or where the amount of the abatement varies.
The rules for calculating the abatement must take into account, in particular,(1) the rate or the combination referred to in the second paragraph of section 244.58 that, according to the rules provided for in subdivision 4, applies in the calculation of the amount of the tax imposed on the unit of assessment concerned;
(2) the basis of imposition of the tax;
(3) the part of the fiscal year during which the vacancy exists.