Free Business Tool Reverse Tax Solver

Reverse Tax Calculator Canada

Q: How do I reverse GST from a total?

Take the tax-included total and divide it by 1 plus the GST rate (or combined rate if other taxes apply). This gives the subtotal before tax, and the difference between total and subtotal is the GST amount.

Q: What is reverse tax calculation?

Reverse tax calculation starts with a tax-included total and works backward to find the pre-tax subtotal and tax portion. It is useful for bookkeeping, reporting, and invoice reconciliation when only final totals are available.

Q: Does this work for HST in Canada?

Yes. This works for HST provinces and also handles GST, PST, and QST combinations based on the province you select, so your reverse calculation reflects the applicable Canadian tax mix.

Calculate pre-tax subtotals from any tax-included total. Instantly strip out GST, HST, PST, or QST based on province-specific rates.

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✓ $113 total → $100 before 13% HST

✓ $115 total → $100 before 15% HST

✓ $105 total → $100 before 5% GST

Example Breakdown

Separate tax from your receipts easily.

Perfect for reconciling bills, tracking expenses, or matching client payments that were paid tax-inclusive.

Total (Tax Included) $115.00

GST/HST portion (15%) $15.00

Subtotal before tax $100.00

Free Calculator

Extract pre-tax amounts instantly.

Enter a tax-inclusive total and select the province to split it into the subtotal and tax portions automatically.

Total amount including tax ($)

Province or Territory

Tax rate applied: 0%

Enter a total and select a province to calculate.

Calculation Results

Outputs update instantly based on inputs.

Subtotal before tax $0.00

Tax amount included $0.00

Total (tax included) $0.00

Formula: subtotal = total ÷ (1 + tax rate).

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Reliable Bookkeeping Tools All calculations utilize official rates verified against current guidelines. For custom invoice generation that applies these rules automatically, try our free Invoice Generator.

Learn More

How to calculate tax backwards in Canada

A reverse tax calculation means starting with a tax-inclusive total and working backwards to extract the pre-tax subtotal and the exact tax amount.

To perform a reverse sales tax calculation in Canada manually, use the following formula:

Subtotal before tax = Total amount ÷ (1 + tax rate decimal)

For instance, if your tax rate is 15% (HST in Atlantic provinces), you convert 15% to 0.15. Then divide the total amount by 1.15 to find the subtotal before tax.

GST/HST Calculator → Free Invoice Generator →

Quick Examples

Reverse HST Calculations

Here is how totals are divided into subtotal and tax portions:

13% HST (Ontario) Example Total Paid: $113.00
Calculation: $113.00 ÷ 1.13 = $100.00 subtotal.
Tax amount is $13.00.

15% HST (NB, NL, PE, NS) Example Total Paid: $115.00
Calculation: $115.00 ÷ 1.15 = $100.00 subtotal.
Tax amount is $15.00.

FAQ

Frequently Asked Questions

How do I reverse GST from a total?

To reverse GST, divide your tax-inclusive total by 1 plus the tax rate (e.g., divide by 1.05 for 5% GST). The result is the pre-tax subtotal. To find the GST portion itself, subtract the subtotal from the total amount.

What is reverse tax calculation?

Reverse tax calculation starts with a final, tax-inclusive price and works backwards to determine the original pre-tax subtotal and the sales tax portion. This is common when businesses receive receipts that do not itemize the sales tax separately.

Does this work for HST in Canada?

Yes. This calculator supports all Canadian tax variants (GST, HST, PST, and QST) depending on the province you select. It automatically configures the correct rate mix so that your calculations remain compliant with regional tax setups.

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