This reverse HST calculator starts from a tax-included total to find the price before tax and the included tax amounts. For example, an Ontario total of $1,130 ÷ 1.13 = $1,000 before tax, with $130 HST. Select the province of supply and confirm which taxes were charged.
Reverse sales tax calculator: start from the total
This calculator needs JavaScript. The rules it uses are on the CRA pages linked below.
The province selector changes the available taxes. For BC, Manitoba and Saskatchewan, select provincial tax only when PST or RST applied. For Quebec, select QST when the price includes it. The tool does not decide whether an item is exempt. To work through a single province in detail, see the Ontario HST calculator, the BC GST and PST calculator, or the Nova Scotia HST calculator.
The reverse-tax formula
Price before tax = tax-included total ÷ (1 + combined applicable rate). Use this formula to calculate reverse sales tax whenever you only have the tax-included total.
Included tax = total − unrounded price before tax. To split separate taxes, multiply the unrounded base by each applicable rate, then round the monetary components.
If only the tax amount is known, price before tax = tax amount ÷ rate; for example, $65 HST ÷ 0.13 = $500 before tax. Extracted HST also splits into its federal and provincial parts at the same rates used to charge it: in Ontario, $130 HST = $50 federal (5%) + $80 provincial (8%).
| Taxes included | Divisor | Example total | Price before tax |
|---|---|---|---|
| 5% GST | 1.05 | $1,050.00 | $1,000.00 |
| Ontario 13% HST | 1.13 | $1,130.00 | $1,000.00 |
| Nova Scotia 14% HST | 1.14 | $1,140.00 | $1,000.00 |
| 15% HST | 1.15 | $1,150.00 | $1,000.00 |
| 5% GST + 7% PST/RST | 1.12 | $1,120.00 | $1,000.00 |
| 5% GST + 6% PST | 1.11 | $1,110.00 | $1,000.00 |
| 5% GST + 9.975% QST | 1.14975 | $1,149.75 | $1,000.00 |
These are standard-rate examples, not taxability decisions. CRA’s guidance explains the GST/HST rate and separate PST base; Revenu Québec explains GST/QST arithmetic.
How do I find the original price before GST?
For a total containing only 5% GST, divide by 1.05. A $105 receipt contains a $100 base and $5 GST. Multiplying $105 by 5% gives $5.25, which is not the tax included in that receipt. The equivalent tax-extraction fraction is 5/105 of the total. Alberta has no provincial sales tax, so 5% GST is the only sales tax there, and zero-rated or exempt items carry none — work through one with the Alberta GST calculator.
Check rounding and mixed-rate purchases
Reverse calculations begin with a total that may already be rounded. The exact reconstructed components can differ by a cent from the supplier’s original lines. For example, a $575 total in Ontario ÷ 1.13 = $508.85 before tax, with $66.15 HST. A basket containing taxable, zero-rated and exempt items cannot generally be split correctly using one divisor on the entire receipt. Separate the relevant subtotals or obtain an itemized invoice.
Can I claim the extracted tax as an ITC?
Arithmetic does not establish eligibility. A GST/HST registrant needs an eligible commercial purchase, tax that meets the applicable rules, and supporting information. Use the actual invoice and CRA’s ITC requirements; do not create a tax credit solely by applying a reverse formula to a bank payment.
To add tax to a new price instead, use the main GST/HST calculator.