If you have a receipt that shows only the final total — the price with tax already included — and you need to know the original price before tax, you need a reverse sales tax calculation. Canadians do this constantly: bookkeepers separating tax for expense claims, freelancers issuing tax-inclusive quotes, shoppers checking a bill, and small business owners preparing GST/HST returns. This guide explains exactly how it works, why the formula is what it is, and how to apply it in each province for 2026.
The Reverse Sales Tax Formula
Everything comes down to one line. To remove tax from a total that already includes it, divide the total by one plus the tax rate:
Tax Amount = Total − Price Before Tax
The reason you divide by 1.13 in Ontario rather than subtracting 13% is subtle but important. The 13% tax was calculated on the pre-tax price, not on the total. If you simply subtracted 13% of the total, you would remove too much. Dividing reverses the original multiplication exactly.
Why subtracting 13% gives the wrong answer
Say the total is $113 in Ontario. The correct pre-tax price is $100. But if you subtract 13% of $113, you get $113 − $14.69 = $98.31 — which is wrong by nearly $1.70. The mistake compounds on larger amounts. Always divide; never subtract the percentage from the total.
Step-by-Step: Reverse HST in Ontario (13%)
- Step 1 — Take your total including tax. Example: $226.00
- Step 2 — Add 1 to the rate: 13% becomes the divisor 1.13
- Step 3 — Divide: $226 ÷ 1.13 = $200.00 pre-tax price
- Step 4 — Subtract to find tax: $226 − $200 = $26.00 HST
- Verify — $200 × 1.13 = $226.00 ✓
Reverse Tax in Every Province (2026)
The method is identical everywhere — only the divisor changes. Here is the combined rate and divisor for each province and territory, using rates current for 2026:
| Province / Territory | Combined Rate | Divide Total By |
|---|---|---|
| Ontario | 13% HST | 1.13 |
| Quebec | 14.975% (GST 5% + QST 9.975%) | 1.14975 |
| British Columbia | 12% (GST 5% + PST 7%) | 1.12 |
| Alberta | 5% GST | 1.05 |
| Saskatchewan | 11% (GST 5% + PST 6%) | 1.11 |
| Manitoba | 12% (GST 5% + PST 7%) | 1.12 |
| Nova Scotia | 14% HST | 1.14 |
| New Brunswick | 15% HST | 1.15 |
| Prince Edward Island | 15% HST | 1.15 |
| Newfoundland & Labrador | 15% HST | 1.15 |
| Yukon / NWT / Nunavut | 5% GST | 1.05 |
Note on Nova Scotia: the HST rate dropped from 15% to 14% on April 1, 2025. Many older calculators still divide by 1.15 for Nova Scotia — that is now incorrect. Use 1.14.
Quebec — a special case
Quebec charges 5% federal GST plus 9.975% provincial QST. Crucially, the QST is calculated on the base price, not on top of the GST — the two are not compounded. So the combined multiplier is simply 1 + 0.05 + 0.09975 = 1.14975. To reverse: $114.98 ÷ 1.14975 = $100.00, giving GST of $5.00 and QST of $9.98.
PST provinces — a warning for businesses
In British Columbia, Saskatchewan and Manitoba, the total combines federal GST with a separate provincial sales tax. You can reverse the full amount to find the pre-tax price, but if you are a registered business claiming input tax credits, remember that only the GST portion is recoverable. The PST is a permanent cost. See our Input Tax Credit guide for the full breakdown.
Common Uses for Reverse Tax Calculation
- Bookkeeping: separating the tax portion of a tax-inclusive receipt for your records and GST/HST return.
- Freelancers & contractors: working out the pre-tax value of an all-in quote.
- Expense reports: employers often need the pre-tax amount and tax shown separately.
- Price checking: confirming a store charged the correct tax on a purchase.
Open the Reverse Sales Tax Calculator →
All rates verified against the Canada Revenue Agency for 2026. This guide is for information only and is not professional tax advice — confirm figures with the CRA or a qualified accountant before filing.