Reverse Sales Tax Calculator

How to remove tax from a total

If you only know the tax-included total — a receipt total, an invoice amount, a price you were quoted — you can work backwards to find the subtotal and the tax using two simple formulas:

• Subtotal = total ÷ (1 + rate)
• Tax = total − subtotal

Type your total into the "Total with tax" field above and pick a province, and this calculator does that division automatically.

Worked example: Ontario, 13% HST

Say you have a $113 total from Ontario. The combined rate is 13%, or 0.13. Subtotal = $113 ÷ 1.13 = $100.00. Tax = $113 − $100.00 = $13.00. So a $113 total in Ontario breaks down to a $100 subtotal and $13 of HST.

Frequently asked questions

How do you remove tax from a total?

Divide the total by (1 + the tax rate) to get the subtotal, then subtract the subtotal from the total to get the tax amount.

Why can't I just multiply the total by the tax rate?

Because the tax rate applies to the subtotal, not the total — multiplying the total by the rate overstates the tax. Dividing by (1 + rate) first is what correctly isolates the subtotal.

Does this work for GST-only provinces too?

Yes — pick Alberta, the Northwest Territories, Nunavut or Yukon and the calculator uses the 5% GST-only rate instead.

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