Eligible losses for Ontario CMT purposes are not affected by changes in the Ontario allocation factor
A corporation that becomes subject to Ontario corporate minimum tax (e.g., as a result of acquiring an Ontario permanent establishment) will be required to determine its eligible losses as if it had been subject to CMT in previous taxation years. There is no provision in the Taxation Act to adjust eligible losses to reflect changes in a corporation’s Ontario allocation factor.
Neal Armstrong. Summary of 15 November 2016 Internal T.I. 2016-0656351I7 under Taxation Act 2007 (Ont.), s. 58(2).