The short answer: a missed CRA instalment accrues interest compounded daily at the CRA's prescribed rate for overdue amounts — 7% for both Q3 and Q4 2026 — from the due date to the day you pay. It is usually a real but modest number, not a cliff: enter your amount below to see it.
Defaults to today. Move it out to see what a later catch-up date would cost instead.
Only matters for whether you owed instalments at all: Quebec’s threshold is net tax owing over $1,800; the rest of Canada uses $3,000. It doesn’t change the interest math below.
Prefilled at 7% — the CRA’s verified rate for both Q3 and Q4 2026 (July–December). The CRA resets this every calendar quarter; edit it if you’re estimating a different quarter.
Interest accrued over 24 days
$11.53
Waiting until your catch-up date adds about $11.53 of instalment interest on $2,500.00, over 24 days late — so you'd owe about $2,511.53 in total. Each additional week you wait from there costs roughly $3.38 more.
Calm and knowable. This is one overdue instalment in isolation — the CRA also credits interest for any instalment you paid early or over the required amount elsewhere in the year, which can offset part of this.
Total to pay
$2,511.53
Cost per extra week
$3.38
A separate penalty may apply
This calculator estimates interest on one instalment. A different, additional instalment penalty can apply only if your total instalment interest for the whole year tops $1,000 — and even then, it’s the greater of $1,000 or 25% of what your interest would have been with no instalments paid at all, subtracted from your actual interest, then halved. Most people paying one late instalment in the low thousands never reach it. See the worked CRA example in the FAQ below.
Estimate, not advice. Interest compounds daily at the CRA prescribed rate you enter above and assumes that rate holds for the whole period — the CRA resets it every calendar quarter. The CRA also nets in contra (credit) interest from any instalment you paid early or over the required amount elsewhere in the year, which this single-instalment estimate can’t see. Confirm your specifics with a Canadian accountant or the CRA.
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A worked example
Say you missed your $2,500 instalment due September 15, 2026, and it stays unpaid all the way to the April 30, 2027 balance-due date — 227 days — at the verified 7% prescribed rate, compounded daily.
| Missed instalment | Due Sep 15, 2026 | $2,500 |
| Days late | To Apr 30, 2027 | 227 |
| Rate | 7%, compounded daily | — |
| Instalment interest | ≈ $111 | |
| Total owed | ≈ $2,611 |
About $111 on $2,500 left unpaid for the better part of a year — real, but rarely disastrous. It also isn't the whole picture: the CRA nets this against contra interest earned on any instalment you paid early or over the required amount, so your actual bill can land lower. Read the full mechanism, including the $1,000 penalty test, in CRA Instalment Interest: How the 7% Actually Works.
Not sure you even owe instalments in the first place? Check the $3,000 / $1,800 threshold test and the four 2026 due dates.
People also ask
What happens if I miss a CRA instalment due date?
The CRA charges instalment interest on the shortfall, compounded daily at the prescribed rate for overdue amounts, from the day the instalment was due until you pay it (or your balance due date, if sooner). It also credits you offsetting "contra" interest for any instalment you paid early or over the required amount elsewhere in the year, so a single missed date isn’t evaluated in isolation. A separate penalty only comes into play if your total instalment interest for the year passes $1,000.
How is CRA instalment interest calculated?
It compounds daily: each day’s interest is added to the balance before the next day’s interest is calculated, at the CRA’s prescribed rate for overdue amounts — 7% for both Q3 2026 (July 1–September 30) and Q4 2026 (October 1–December 31). The rate resets every calendar quarter, so a payment due in a later quarter can use a different rate once the CRA publishes it.
Does paying late instalments always trigger a penalty?
No. An instalment penalty applies only if your total instalment interest charges for the year are more than $1,000. Below that line, you owe the interest itself and nothing more. When the penalty does apply, the CRA takes the greater of $1,000 or 25% of what your interest would have been with no instalments paid at all, subtracts that from your actual instalment interest, and halves the difference — on the CRA’s own example, $2,500 of actual interest against a $3,200 no-instalment baseline produces a $750 penalty.
Do I get credit for paying other instalments early or extra?
Yes. The CRA calculates contra (credit) interest on instalments you paid early or over the required amount, and nets that against interest owed on a late or short instalment elsewhere in the same year. This calculator estimates one instalment on its own — your real CRA interest charge can come in lower once contra interest from your other payments is factored in.
What are the 2026 CRA instalment due dates?
For individuals: March 15, June 15, September 15, and December 15, 2026. An instalment is a payment you initiate — it isn’t a bill that arrives in the mail, though the CRA does mail reminders with suggested amounts based on your past returns.
Is this calculator official tax advice?
No. It applies the CRA’s verified daily-compounding convention and prescribed rate to a single missed or upcoming instalment to give a plain-language estimate. It doesn’t see your full-year instalment history, so it can’t net in contra interest from other quarters, and its penalty note is deliberately labelled "may apply." Confirm your specifics with a Canadian accountant or the CRA.
Sources
Every rate and rule in this calculator is transcribed directly from the CRA (verified 21 September 2026):
- CRA — Prescribed interest rates and the Q3 2026 and Q4 2026 quarter pages — the 7% rate on overdue amounts (incl. instalments) used above, confirmed for both quarters.
- CRA — Interest and penalty charges on instalments — the daily-compounding mechanism, contra (credit) interest, and the $1,000 instalment-penalty formula and worked example used in the FAQ above.
- CRA — Who has to pay tax instalments — the four 2026 due dates and the $3,000 / $1,800-Quebec net-tax-owing threshold.
VRITTI keeps the dates so this stays rare.
The app grows a CRA set-aside in the background and flags each instalment date before it arrives — so catching up is the exception, not the routine.
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