The amount of active small business income eligible for the Ontario low rate of corporate tax is $400,000. Ontario levies a surtax (on companies that claim the Ontario small business rate) where taxable income exceeds income eligible for these low rates. The small business rates, income threshold eligible for low rates, surtax thresholds and surtax rates are as follows:

Companies with active business income will bear a low marginal rate on income up to the income threshold eligible for low rates, and a high marginal rate (general rate plus surtax) on income within the surtax threshold range. Income in excess of the surtax threshold will be taxable at the general rate or M & P rate, as applicable.