Reverse sales tax calculator

Why you cannot just subtract 13%

You have a receipt for $100.00 in Ontario and you need the price before tax. The instinct is to take 13% off the total. That gives $87.00, and it is wrong by $1.50.

The reason is that the tax was never calculated on $100.00. It was calculated on the smaller number — the pre-tax price — and then added. So to undo it you divide by 1.13, not subtract a percentage. The right answer is $88.50 before tax and $11.50 of tax.

The error is proportional, so it grows with the receipt: on $10,000 it is $149.56. It is the single most common arithmetic mistake in expense claims, and it always goes the same way — understating the pre-tax cost, and therefore the tax you could claim back.

When you actually need this

Expense claims and bookkeeping. A business reclaims the GST/HST it paid as an input tax credit, and to do that it needs the tax split out. A till receipt that only shows a total forces the calculation.

Invoicing backwards from a round number. Quoting "$1,000 all in" means the price before tax is $884.96, not $1,000. Get that wrong on a quote and the difference comes out of your margin.

Checking a receipt. Dividing the total and comparing the tax line is the fastest way to spot a till charging the wrong rate — which happens most often in the months after a rate change.

The arithmetic, in full

For Ontario, with a combined rate of 13%:

Price before tax = total ÷ 1.13

HST = price before tax × 0.13

Worked on $100.00: $100.00 ÷ 1.13 = $88.50, of which $11.50 tax.

There is only one tax to reverse here, which makes Ontario the easy case.

The divisor for all 13 jurisdictions

The whole operation is one division, and the only thing that changes from one province to the next is what you divide by. Cheapest first:

Alberta — divide by 1.05. 5% GST and no provincial tax at all.

Northwest Territories — divide by 1.05. 5% GST and no provincial tax at all.

Nunavut — divide by 1.05. 5% GST and no provincial tax at all.

Yukon — divide by 1.05. 5% GST and no provincial tax at all.

Saskatchewan — divide by 1.11. 5% GST plus 6% PST, both on the same base.

British Columbia — divide by 1.12. 5% GST plus 7% PST, both on the same base.

Manitoba — divide by 1.12. 5% GST plus 7% RST, both on the same base.

Ontario — divide by 1.13. A single 13% HST.

Nova Scotia — divide by 1.14. A single 14% HST.

Quebec — divide by 1.14975. 5% GST plus 9.975% QST, both on the same base.

New Brunswick — divide by 1.15. A single 15% HST.

Newfoundland and Labrador — divide by 1.15. A single 15% HST.

Prince Edward Island — divide by 1.15. A single 15% HST.

Three shapes, and they matter for what comes out the other side. In the 4 places with GST only the division gives you a base and one tax figure, and you are done. In the 5 HST provinces you also get one figure, but it is a blended one that has the federal 5% buried inside it. Only in the 4 with a separate provincial tax does the division have to be followed by a split — and that split is the part that decides how much money you get back.

Why anyone does this: the receipt that is allowed not to tell you

Almost nobody reverses a receipt out of curiosity. They do it because a registered business recovers the GST/HST it paid through an input tax credit, and to claim one it needs the tax as a separate figure.

Which runs into the thing that makes this page necessary. Below $100, the receipt is not required to show the tax at all. The Canada Revenue Agency asks for three things on a purchase under that amount: the supplier’s name or trading name, the date of the invoice, the total amount paid or payable. That is the whole list. So the corner-shop receipt in your wallet is not badly made — it is complying, and the tax has to be derived by dividing.

From $100 the requirements step up: you also need the supplier’s GST/HST registration number and an indication of the total amount of GST/HST charged. And from $500, on top of that, the buyer’s name or trading name, a brief description of the property or services, the terms of payment. So the receipts you most need to reverse are precisely the small ones, where the law asks least.

And in British Columbia there is a second reason the split matters, which costs real money: the 5% GST comes back and the 7% PST does not. Provincial sales tax is not an input tax credit for a GST/HST registrant. On a $100.00 receipt that divides into $89.29 before tax, $4.46 of GST and $6.25 of PST, only the $4.46 is recoverable — the $6.25 is a cost of doing business like any other.

A single division by 1.12 gives you $10.71 of "tax" and stops there. Claim that as an input tax credit and you have over-claimed by $6.25 on every hundred dollars you spend.

Read off CRA — Input tax credits, and the documentary requirements that apply by amount of the purchase, on 2026-09-21.

Backing out, removing, reversing — and the one that means something else

This operation has more names than it has steps, and they all describe the same division. Backing out the tax, removing it, reversing it, working out the pre-tax price, the price before tax, the inverse or backward calculation, subtracting tax from a total — one arithmetic operation, seven labels, and people reach for whichever one their bookkeeper used.

Two of them are worth pinning down because they are used loosely and mean different things.

"Net of tax" is not this. In accounting it usually means after income tax, not after sales tax, and a figure described as net of tax in a set of accounts is very unlikely to be the number you get by dividing a till receipt. If someone asks for a figure net of tax, ask which tax.

"Tax-inclusive" and "tax-exclusive" pricing describe which number you were quoted, not an operation. A tax-inclusive price is the total — the one you divide. A tax-exclusive price is the base — the one you multiply. Almost every dispute about a quote is really a disagreement about which of the two was meant, and the gap between them is exactly the tax.

The distinction that actually matters is none of these: it is divide, do not subtract. Everything else is vocabulary.

The cent that will not reconcile

If you reverse receipts one at a time this never comes up. If you reverse a hundred of them into a ledger, it comes up on the first afternoon.

The total you start from was already rounded to the cent when the till printed it. Dividing it gives a base with more decimal places than money has, and rounding that to the cent leaves a figure which, multiplied back up, does not always return the total you started with.

In Quebec, at 14.975%: a total of $11.71 reverses to $10.18 before tax. Put 14.975% back on $10.18 and you get $11.70 — a cent adrift from where you began. Neither figure is wrong; the cent was lost when the till rounded, and no arithmetic gets it back.

Which is why bookkeeping software posts the tax as the difference between the total and the rounded base, rather than calculating it from the base directly. The total is the figure that actually changed hands and it is the one that has to be right; the base absorbs the rounding. This calculator shows both, and on a receipt where they disagree by a cent, the total wins.

It also means a reversed figure should never be used to check whether a shop charged the correct rate on a small purchase — a cent of difference proves nothing. On a $2,000 invoice it would; on an $11.71 receipt it is just rounding.

The receipt where dividing gives the wrong answer

Everything above assumes one thing, and it is worth saying out loud: that every line on the receipt was taxed at the same rate. On a great many Canadian receipts it was not, and then no single division can recover the split.

Zero-rated goods are the common case. Basic groceries, prescription drugs and most medical devices carry GST/HST at zero per cent — not exempt, formally, but rated at zero, which is the same thing at the till and a different thing on the seller's return. So a supermarket bill is two receipts printed as one.

Put numbers on it. A $105.20 Ontario shop made of $60.00 of basic groceries and $40.00 of taxable goods carries $5.20 of tax — all of it on the $40.00. Divide the $105.20 total by 1.13 and you get $93.10 before tax and $12.10 of tax: $6.90 more tax than was actually charged, invented out of groceries that were never taxed.

The tell is on the receipt itself. A till that handles mixed baskets prints the taxable subtotal separately, usually flagged line by line with a letter. Where that subtotal exists, use it and skip the division entirely — you are not deriving anything, you are reading it.

And the case that looks like a till error and is not. Ontario refunds its provincial share at the point of sale on books, children's clothing and footwear, children's diapers, children's car seats, qualifying newspapers, qualifying food and beverages, so those lines come through at the federal 5% while everything else on the same receipt carries the full 13%. Three rates on one piece of paper, and the total tells you about none of them.

Either way this is the point at which a calculator stops being the right tool and the taxable subtotal printed on the paper becomes the only honest source.

And when the paper does not carry one — an old till roll, a handwritten receipt — the answer is not to divide anyway. It is to add up the taxable lines yourself and reverse that subtotal, which is the same division applied to the right number. The arithmetic on this page was never the difficult part; knowing which figure to feed it is.

Where the split is the hard part

Four jurisdictions charge two taxes on the same base, and they are the ones where a single division is not the whole answer — you divide once, then split the result in two, because only half of it is recoverable.

Saskatchewan — divide $100.00 by 1.11 to get $90.09, then split the $9.91 of tax into $4.50 of GST and $5.41 of PST. Only the GST comes back.

British Columbia — divide $100.00 by 1.12 to get $89.29, then split the $10.71 of tax into $4.46 of GST and $6.25 of PST. Only the GST comes back.

Manitoba — divide $100.00 by 1.12 to get $89.29, then split the $10.71 of tax into $4.46 of GST and $6.25 of RST. Only the GST comes back.

Quebec — divide $100.00 by 1.14975 to get $86.98, then split the $13.02 of tax into $4.35 of GST and $8.68 of QST. Only the GST comes back.

Quebec is the one people get wrong most often, and not because of the odd rate. The QST is charged on the price excluding the GST, not on the GST-inclusive amount — the two sit side by side on the same base. So the divisor is 1.14975, one division, and not two in sequence.

Questions

How do I remove 13% tax from a total in Ontario?

Divide by 1.13. A $100.00 total is $88.50 before tax and $11.50 of tax. Subtracting 13% from the total instead gives $87.00, which is wrong by $1.50.

Why is subtracting the percentage wrong?

Because the tax was calculated on the pre-tax price, not on the total. Taking 13% off the total removes 13% of a bigger number than the one the tax was worked out on, so you take away too much. The error is proportional and grows with the receipt.

Does this work for a receipt with exempt items on it?

No, and that is the real limitation. If part of the bill was zero-rated — groceries, prescriptions — the tax was charged on only part of the total, and dividing the whole thing gives the wrong split. This works for a receipt where everything was taxable.

How do I back out sales tax from a total?

Divide, do not subtract. Take the total and divide it by one plus the combined rate: Alberta 1.05, Northwest Territories 1.05, Nunavut 1.05, Yukon 1.05, and so on for all 13. In Ontario a $100.00 total backs out to $88.50 before tax.

What is the formula to remove tax from a price?

Price before tax = total ÷ (1 + rate). Tax = total − price before tax. The second line matters: working the tax out from the base instead can leave you a cent adrift, because the total was already rounded when it was printed.

How do I separate GST and PST from one total?

One division, then a split. In British Columbia divide $100.00 by 1.12 to get $89.29, then apply each rate to that base: $4.46 of GST and $6.25 of PST. Do not reverse them one at a time — both were charged on the same pre-tax price, not one on top of the other.

Can I claim back the PST as well as the GST?

No. A GST/HST registrant recovers the GST or HST through an input tax credit; provincial sales tax is not recoverable. On a $100.00 British Columbia receipt that is $4.46 back and $6.25 gone. Read off the CRA's input tax credits guidance on 2026-09-21.

Why does my receipt not show the tax?

Because under $100 it does not have to. The CRA's documentary requirements for a purchase below that amount are the supplier's name, the date and the total — nothing more. The tax has to be derived, which is what this calculator is for. From $100 the receipt must also show the GST/HST registration number and the tax charged.

How do I reverse the QST in Quebec?

Divide by 1.14975 — once, not twice. The QST is charged on the price excluding the GST, so the two taxes sit side by side on the same base rather than compounding. A $100.00 total is $86.98 before tax, $4.35 GST and $8.68 QST.

Is "net of tax" the same as the price before sales tax?

Usually not. In accounting "net of tax" normally means after income tax, not after sales tax, so a figure described that way in a set of accounts is rarely the number you get by dividing a till receipt. If someone asks for a figure net of tax, ask which tax they mean.