Income Tax Act subsection 125

The small business deduction is available on active business income for a Canadian Controlled Private Corporation. It provides a reduction in the corporate tax rate up to the federal limit of $500,000.

What the above means is if you are earning active business income as a CCPC then your first $500,000 of net income is taxed at a reduced rate. This makes it easier to amass funds in a corporation and is a large reason many Canadians incorporate their businesses.