Quebec pays instalments twice: how the CRA and Revenu Québec systems stack

Everywhere else in Canada, tax instalments mean one agency, one reminder, one set of quarterly payments. In Quebec it's all doubled: the CRA collects federal instalments, Revenu Québec collects provincial ones, and each runs its own reminders, its own math, and its own interest — including one rule with real teeth that exists nowhere else in the country.

Two systems, same calendar

Both agencies use the same due dates — March 15, June 15, September 15, December 15 — and the same basic structure: quarterly prepayments of tax that nothing is withholding.

• CRA (federal): required when your federal net tax owing is more than $1,800 this year and in 2025 or 2024. Note the number — for Quebec residents the federal threshold drops from the $3,000 used everywhere else, because Ottawa collects a smaller share of a Quebecer's total tax.
• Revenu Québec (provincial): required when your estimated Québec net income tax payable is over $1,800 this year and was over $1,800 in either of the two previous years. RQ's instalment concept sweeps in more than income tax: QPP contributions, the health services fund, and drug/parental insurance premiums ride along.

Cross both thresholds — common for self-employed Quebecers and retirees drawing RRIF income — and you're making eight payments a year to two different payees. The CRA side arrives on its familiar reminders; RQ's come with form TP-1026 amounts and are paid to Revenu Québec, not to Ottawa. Paying one agency does nothing for the other.

The rule with teeth: RQ's extra 10%

Both agencies charge interest on late or short instalments at their prescribed rates, compounded daily. But Revenu Québec adds something the CRA has no equivalent for: if an instalment payment is less than 75% of what was due, RQ charges an additional 10% per year, capitalized daily, on top of the regular interest.

Miss a $2,000 RQ instalment badly enough and you're not paying one interest rate — you're paying two, stacked. On the federal side, a comparable miss accrues the prescribed 7% (Q3 2026) and a penalty only once instalment interest tops $1,000. In Quebec, the punishment arrives much sooner and much faster. If cash is tight in a quarter, shorting both agencies equally is the worst strategy — getting each payment above RQ's 75% line before optimizing anything else avoids the stacked rate.

Escaping both systems at once

The exits work the same as everywhere, just twice:

• More withholding at source. RRIF and pension payers can withhold extra for both levels of tax. Push each agency's net tax owing under $1,800 and both instalment obligations fall away. For retirees this is usually the cleanest fix.
• The current-year option exists on both sides. Income dropping? Both the CRA and RQ let you pay based on this year's estimate instead of the reminder amounts — with interest exposure on both if you lowball.
• The reminder amounts carry the no-interest guarantee on both sides when paid in full and on time.

The starting number is the same either way: what your income generates in combined tax and what's already withheld. Your take-home pay breakdown for Quebec shows the combined federal-provincial bite at your income — the raw material for both agencies' tests. The instalment calculator applies the lower $1,800 threshold Quebec residents are measured against on the federal side, and flags the Revenu Québec obligation running alongside it. The general mechanics of the federal side are covered in who actually has to pay and the three calculation options.

The takeaway

In Quebec, "am I paying my instalments?" is two questions. Two agencies, both triggered at $1,800, both due the same four days — and only one of them charges an extra 10% the moment a payment slips under 75% of what it should have been. Budget for eight payments, keep RQ above its 75% line, and let extra withholding shrink both problems at once.