The Ontario small business deduction (SBD) reduces the amount of income tax certain types of firms pay. Firms that are categorized as small businesses pay a lower rate on the first $500,000 of their turnover. As of January 1st, 2020, the lower rate of Ontario corporate income tax is 3.2 percent instead of 3.5 percent. But you have to qualify to secure the deduction. An experienced CPA can help you to do that.