CRA Tax Instalments After a One-Off Capital Gain
You sold a non-registered stock or some other position this year, the gain was large, and nothing was withheld on it. Now you’re doing the arithmetic on what you’ll owe and wondering if the Canada Revenue Agency is about to put you on quarterly tax instalments. It isn’t, not for the year you sold. A single one-off capital gain does not put you on CRA tax instalments in the year you realize it. The reminder that eventually shows up lands in August of the following year, and it asks for the whole amount again, all at once, in a year the gain almost certainly will not repeat.
The Two-Sided Test That Decides If You Owe Instalments
CRA’s own guide, “Required tax instalments for individuals: Who has to pay” (page last updated January 20, 2026), sets the test as two conditions that must both be true: net tax owing above $3,000 (or $1,800 in Quebec) in the current year, and net tax owing above that same threshold in at least one of the two preceding years. The underlying law, section 156.1(2)(b) of the Income Tax Act, states it more precisely: a year is exempt where “the individual’s net tax owing for the particular year, or for each of the 2 preceding taxation years, does not exceed the individual’s instalment threshold.”
“Net tax owing” is the number that does all the work here: total federal and provincial tax payable, less whatever was deducted or withheld at source under section 153. A salary with tax already taken off doesn’t add to it. An untaxed capital gain does, because as CRA notes, “Income tax cannot be withheld from certain types of income, such as self-employment, investment, rental income, and capital gains.” If that’s new to you, our guide to how investment income is taxed in Canada explains why only half a capital gain is taxable in the first place.
A reminder letter is a suggestion, not an assessment: the obligation comes from section 156.1(2), not the letter. If your current year’s net tax owing will be $3,000 or less ($1,800 or less in Quebec), you owe nothing regardless of what the reminder says.
What This Looks Like With Real Numbers
Take an Ontario resident earning a $95,000 salary with tax withheld at source, who sells a non-registered position in 2026 for a capital gain of $90,000, with nothing withheld on the sale. Under section 38(a), half the gain is taxable: $45,000.00. Tax on the $95,000 salary alone works out to $19,196.55; tax on the combined $140,000 works out to $36,534.68. Both figures are federal plus Ontario tax before the Ontario Health Premium and CPP and EI, which are identical at both income levels and so cancel out of the difference. The difference, $17,338.13, is the 2026 net tax owing created entirely by the gain: 19.26% of the $90,000 gain, or 38.53% of the taxable half.
Because 2024 and 2025 were both fully-withheld salary years, net tax owing in each was $0. Are instalments required for 2026? No. The current year clears $3,000, but neither of the two preceding years does, so section 156.1(2)(b) exempts the year entirely. The full $17,338.13 is due on the balance-due day, April 30, 2027, and not a dollar earlier.
Why the Money Lands in September and December, Not March or June
Section 156(1)(b) of the Act is the mechanical piece almost nobody writes up. It sets the March 15 and June 15 instalments at one quarter of an amount tied to your net tax owing from two years back, and the September 15 and December 15 instalments at half the amount by which last year’s figure exceeds half of that two-years-back figure. The consequence for a gain realized in 2026: it cannot reach the March or June 2027 instalments at all, because those are built on 2025, a year the gain didn’t touch. It lands entirely on September 15 and December 15, 2027, through the August 2027 reminder.
What the August 2027 Reminder Asks For
The February 2027 reminder brings nothing, because March and June are built on 2025, a $0 net tax owing year. The August 2027 reminder is where the $17,338.13 shows up, split across September 15 and December 15, 2027, using one of three methods described in CRA’s guide to calculating your instalments: letting CRA base the payments on your latest assessed return, splitting the total based on your prior year’s result, or estimating the current year yourself.
| Option | September 15, 2027 | December 15, 2027 | 2027 total |
|---|---|---|---|
| No-calculation (CRA’s default, based on your latest assessment) | $8,669.06 | $8,669.06 | $17,338.13 |
| Prior-year (same total, split 75/25) | $13,003.60 | $4,334.53 | $17,338.13 |
| Current-year (your own estimate, split 75/25) | 75% of your estimate | 25% of your estimate | Your estimate |
Both fixed options land on the same $17,338.13, since both are anchored to the gain year itself. The current-year option is the only one that can come in lower, and it depends on getting a working estimate of 2027 net tax owing right. That’s exactly the number our capital gains tax calculator is built to help you estimate before you commit to a payment method.
If Your Estimate Turns Out Too Low
The current-year option is appealing if you know 2027 won’t look like the gain year, but the downside is bounded by law, not by the reminder’s number. Under section 161(4.01), CRA calculates interest on “whichever method gives rise to the least total amount of such parts or instalments,” and it only charges the difference “if more than $25.”
Say 2027 net tax owing actually lands at $8,000 and nothing was paid during the year. Interest runs on the cheapest of the three options, here four payments of $2,000.00, not the $17,338.13 the August reminder asked for. At 7%, the rate CRA prescribed for the fourth quarter of 2026, compounded daily (the rate resets every quarter; this is not a claim about 2027 or 2028), carried to the April 30, 2028 balance-due day:
- $2,000.00 due March 15, 2027, 412 days: $164.42
- $2,000.00 due June 15, 2027, 320 days: $126.57
- $2,000.00 due September 15, 2027, 228 days: $89.38
- $2,000.00 due December 15, 2027, 137 days: $53.24
- Total instalment interest: $433.62
The escape hatch also re-runs every year. At a 2027 net tax owing of $2,500 or $3,000, no instalments are required for 2027 at all; at $3,001 or $8,000, they are.
When the Penalty Starts to Bite
Interest alone doesn’t trigger a penalty. Section 163.1 of the Income Tax Act sets the penalty at half of the amount by which actual instalment interest exceeds the greater of $1,000 and 25% of what the interest would have been if no instalment had been paid at all. In CRA’s worked example on its page on interest and penalty charges, actual instalment interest of $2,500 against a hypothetical $3,200 with no instalments paid produces a $750 penalty: the $1,000 floor beats 25% of $3,200 ($800), so $2,500 minus $1,000, halved, equals $750.
Interest below $1,000 produces no penalty at all under that floor; the $433.62 above stays well under it, so the penalty here is $0.00. A single missed September 15 instalment would need to be roughly $22,376 before the interest alone reached $1,000, at 7% over the 228 days to the balance-due day.
The TFSA Difference, and Where Quebec Diverges
None of this machinery ever activates for a gain realized inside a TFSA, because a TFSA gain is never taxed and so never becomes part of net tax owing in the first place. If you’re deciding where to hold a position that might appreciate sharply, our guide to TFSA rules covers what qualifies and how contribution room works.
Quebec residents face a lower federal threshold, $1,800 instead of $3,000, based on the province you live in on December 31; Revenu Quebec runs a separate provincial instalment system on top of the federal one, which this piece doesn’t cover.
Running the Test on Your Own Numbers
Farmers and fishers whose main income comes from farming or fishing pay once a year, on December 31, with a reminder in November instead of the February and August cycle. You can also avoid instalments altogether by increasing withholding directly, using form ISP3520OAS for OAS, ISP3520CPP for CPP, or a TD1 with an employer or pension administrator.
Disclaimer: The content on bestcanadianstocks.ca is for informational and entertainment purposes only and does not constitute financial advice. Past performance is not indicative of future results. Always consult a qualified financial advisor before making investment decisions. Income Tax Act sections 38, 153, 156, 156.1, 161 and 163.1, and Income Tax Regulations section 5300, from Justice Laws Canada, retrieved September 21, 2026; the Act as retrieved is current to July 21, 2026 and last amended June 18, 2026. Canada Revenue Agency, ‘Required tax instalments for individuals’ (Who has to pay, Payment due dates, Options to calculate, Interest and penalty charges), all pages last updated January 20, 2026 and retrieved September 21, 2026. Prescribed interest rate of 7% on overdue taxes from the CRA prescribed interest rates announcement for the fourth calendar quarter of 2026, retrieved September 21, 2026; the rate is reset quarterly. Federal and Ontario 2026 brackets from the Canada Revenue Agency, ‘Current year tax rates and income brackets (2026)’; federal basic personal amount $16,452 and Ontario basic personal amount $12,989 and Ontario surtax thresholds from CRA guide T4032ON, January 2026 edition. All tax arithmetic is ours, calculated from those sources; the worked example is federal plus Ontario tax before the Ontario Health Premium and CPP and EI.
