How Canadian sales tax works
Canada runs two parallel sales-tax systems. The federal GST is a 5% value-added tax that applies across the country. In five provinces it is harmonised with the provincial sales tax into a single HST, administered by the CRA. In the remaining provinces, GST is charged on top of a separate PST administered by each province (or QST in Quebec, administered by Revenu Quebec).
HST provinces
Single combined rate, remitted to the CRA: Ontario 13%, Nova Scotia 14%, New Brunswick 15%, Newfoundland and Labrador 15%, Prince Edward Island 15%.
GST only
Federal GST 5% with no provincial sales tax: Alberta, Northwest Territories, Nunavut, Yukon.
GST plus PST
Federal GST 5% plus a separate provincial sales tax administered by the province: BC (PST 7%), Saskatchewan (PST 6%), Manitoba (RST 7%).
GST plus QST (Quebec)
Federal GST 5% plus Quebec Sales Tax 9.975%. Both apply to the same pre-tax base under the non-cascading rule that took effect 1 January 2013.
Recoverable vs non-recoverable
GST and HST are input tax credits: a registered business recovers the tax it paid on its inputs against the tax it collected from its sales. QST in Quebec is also recoverable through Revenu Quebec's input-tax-refund system. PST in BC, SK, and MB is not recoverable; it lands as a cost in the books. The calculator splits the result so you can code the recoverable and non-recoverable portions to the right accounts.
Common scenarios
Ontario invoice. Net of $100 plus HST 13% gives $113 gross with $13 of recoverable HST. One line, one rate, single remittance to the CRA.
British Columbia invoice. Net of $100 plus GST 5% plus PST 7% gives $112 gross. The $5 GST is recoverable as an ITC; the $7 PST sits as a business cost.
Quebec invoice. Net of $100 plus GST 5% plus QST 9.975% gives $114.98 gross (non-cascading: both taxes apply to the pre-tax $100). Both the $5 GST and the $9.98 QST are recoverable.
Alberta invoice. Net of $100 plus GST 5% gives $105 gross. No PST. The $5 GST is recoverable.