Reverse HST Calculator

What is Reverse Sales Tax?

Usually, when we shop, we take the price tag and add the sales tax to find out how much we need to pay. Reverse sales tax calculation is simply doing this in reverse: taking the final amount you paid and stripping away the taxes to reveal the original base price.

This is crucial because the tax amount is not always clearly listed on credit card statements or cash transaction slips, even though you paid it.

The Reverse Tax Formula

Calculating tax backwards isn't as simple as subtracting the percentage. If you paid $113 where tax is 13%, subtracting 13% gives you $98.31, which is incorrect (the base price was $100).

Steps:

1. Convert the tax percentage to a decimal (e.g., 13% = 0.13).
2. Add 1 to the decimal (1 + 0.13 = 1.13).
3. Divide the total price by this number.

To find the Tax Amount only:
Total Price - Pre-Tax Price = Tax Paid.

Calculation Examples by Province

Ontario (13% HST)

Suppose you bought a coffee maker for $56.50 (tax included).

• $56.50 ÷ 1.13 = $50.00 (Base Price)
• $56.50 - $50.00 = $6.50 (HST Paid)

British Columbia (5% GST + 7% PST = 12%)

Suppose you paid $112.00 for a service.

• $112.00 ÷ 1.12 = $100.00 (Base Price)
• $112.00 - $100.00 = $12.00 (Total Tax)
• $100.00 × 0.05 = $5.00 (GST)
• $100.00 × 0.07 = $7.00 (PST)

Alberta (5% GST Only)

Suppose you paid $21.00 for lunch.

• $21.00 ÷ 1.05 = $20.00 (Base Price)
• $21.00 - $20.00 = $1.00 (GST Paid)

Why Do You Need This?

Reverse tax calculations are indispensable in several scenarios:

• Lost Receipts: If you lost the itemized receipt but see the charge on your bank statement, you can back-calculate the tax to record it properly.
• Cash Deals: Sometimes prices are negotiated as "cash flat," but for accounting, you still need to record the implied tax if registered.
• Reimbursements: When splitting a bill with friends or colleagues where some items were taxable and others weren't.
• Invoicing: If a client gives you a fixed budget (e.g., "I have $500 total to spend"), you can calculate what your actual service fee should be.

Business & Bookkeeping Tips

For business owners, getting this right means money in your pocket.

claiming ITCs (Input Tax Credits): You can only claim the GST/HST you actualy paid. If you enter the full amount of an expense as "office supplies" without stripping out the tax, you are:

1. Overstating your expense (which lowers profit).
2. Missing out on the direct tax refund (ITC) which is dollar-for-dollar value.

Using a reverse calculator ensures you separate the Net Expense from the Recoverable Tax.

Frequently Asked Questions