How to Use the GST/HST Calculator

Before You Start

• Identify the customer's province — for goods shipped inter-provincially, you generally charge the destination province's rate.
• Know whether you are starting with the pre-tax amount (forward) or a total already-paid amount (reverse).
• For Quebec, note that GST and QST are calculated separately and are not compounded on each other.

Step-by-Step

1. Select the customer's province: Tax is charged at the rate of the province where the supply is made or delivered.
2. Choose forward or reverse mode: Forward: you have the pre-tax price and need to add tax. Reverse: you have the total amount paid and need to back out what the pre-tax price was.
3. Add line items: Click "Add Line" for each service or product. Give each a description and amount. All lines use the same province rate.
4. Toggle PST/QST if needed: Uncheck the provincial tax toggle if your supply is exempt from PST/QST (e.g., many B2B services in some provinces).
5. Review breakdown: The tax breakdown panel shows each tax component separately. The line item table shows per-line totals.

How to Read the Output

• For HST provinces (Ontario, NS, NB, NL, PE), there is only one combined tax — GST and provincial are not shown separately.
• For PST provinces (BC, MB, SK) and Quebec (QST), the federal and provincial taxes are separate lines.
• The effective tax rate shown will match your province's posted rate when all taxes are applied.

Common Mistakes to Avoid

• Using your own province's rate instead of the customer's province for shipped goods.
• Compounding QST on top of GST-inclusive price — QST applies to the pre-GST amount, not the GST-inclusive total.
• Forgetting that some supplies (basic groceries, most healthcare, financial services) are zero-rated or exempt and should not have tax applied.