GST/QST Sales Tax Calculator (Quebec 2026)

In Quebec two sales taxes are added to the selling price: 5% GST and 9.975% QST, for a combined rate of 14.975%. Enter an amount before taxes below and instantly get each tax and the total to invoice. Everything runs in your browser — no signup, no data sent anywhere.

How are sales taxes calculated in Quebec?

The calculation happens in two steps, both on the pre-tax amount:

1. GST = amount × 5%
2. QST = amount × 9.975%
3. Total = amount + GST + QST

Take a $100 invoice before taxes:

• GST: $100 × 0.05 = $5.00
• QST: $100 × 0.09975 = $9.975, rounded to $9.98
• Total to invoice: $114.98

Each tax line is rounded separately to two decimals. If the third decimal is less than 5, round down; if it is 5 or more, round up. That is the method Revenu Québec expects on an invoice, and the one this calculator applies.

A common mistake is to add the two rates together (14.975%) and then split the result. The total comes out the same, but the two tax lines can end up a cent away from what your accounting software computes — a discrepancy that then propagates into your returns.

Quebec sales tax rates in 2026

Tax	Rate	Applied to
GST (goods and services tax)	5%	Pre-tax amount
QST (Québec sales tax)	9.975%	Pre-tax amount
Combined rate	14.975%

These rates have been unchanged since January 1, 2013. That is also the date QST stopped being calculated on an amount that already included GST: there is no longer any tax-on-tax effect in Quebec. Before 2013 the effective rate was slightly higher than the sum of the two posted rates.

Who has to charge GST and QST?

You must register for the GST and QST files as soon as your taxable supplies exceed $30,000 over four consecutive calendar quarters. The threshold is a rolling one: it does not reset on January 1, it is assessed over the last four quarters.

Three situations to know:

• Below the threshold — you are a “small supplier”. Registration is optional and you do not charge taxes.
• Threshold crossed over four quarters — you must register and start collecting taxes.
• Threshold crossed within a single quarter — the obligation is immediate, with no grace period.

Registering voluntarily while below the threshold has a real upside: it entitles you to input tax credits (ITC) and input tax refunds (ITR), meaning you recover the taxes paid on your business purchases. For a business with significant expenses, that can beat staying a small supplier.

What an invoice must show

As soon as you charge taxes, your invoice must display:

• your GST and QST registration numbers (formats 123456789 RT0001 and 1234567890 TQ0001);
• the pre-tax amount;
• GST and QST on separate lines, with their rates;
• the total including all taxes.

A client who is registered for the tax files needs this information to claim their own ITCs and ITRs. An incomplete invoice can be rejected during an audit — and you are the one they will call.

 What if I only know the total?

That is the reverse situation: you have a receipt showing only a tax-included amount and you need the pre-tax figure for your books. Divide the total by 1.14975.

Our reverse sales tax calculator does it automatically and breaks out the GST and QST included in the amount.