MPAC (or Municipal Property Assessment Corporation) describes its role as: The Municipal Property Assessment Corporation (MPAC) is responsible for assessing all property in Ontario. It operates under the authority of the Municipal Property Assessment Corporation Act. Every municipality in Ontario is a member of the Corporation, which is governed by a Board of Directors. MPAC does not set assessment policy but it does administer these policies. Its main responsibility is to calculate assessed values, and to classify properties according to their use, for each of the over four million properties in Ontario. These values are provided to municipalities on annual assessment rolls. Municipalities and the Province use these values when they calculate property taxes and education taxes.