The highest marginal federal tax rate in Canada is 33% and the highest marginal provincial tax rate in Ontario is 13.16% (source: Government of Canada tax rates webpage)
Adding these together, the highest marginal tax rate should be 46.16% in Ontario. However, I live in Ontario and am paying a 53.53% marginal tax rate. This is also listed as the highest combined marginal rate by multiple sources, even ones that repeat the 33% and 13.16% values (example). Why is it 53.53% and not 46.16%? Is there an established formula for calculating a marginal tax rate since it doesn't seem to just be federal rate + provincial rate?