The HST for Ontario is calculated from Ontario rate (8%) and Canada rate (5%) for a total of 13%. This rate is the same since july 1st 2010.
Amount with sales tax / (1+ (HST rate/100)) = Amount without sales tax
Amount without sales tax x (HST rate/100) = Amount of HST in Ontario
100$ / (1+(13/100)) = 88.50$ (88,495575$)
88,495575$ x (13/100) = 11.50$
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