CRA Tax Instalments Due September 15, 2026: The $3,000 Rule and What Missing One Costs

Who Actually Has to Pay a Tax Instalment

You have to pay 2026 tax by instalments if two things are both true. First, your 2026 net tax owing — roughly, what you would owe CRA at filing after withholding, credits, and prior payments — comes to more than $3,000, or more than $1,800 if you lived in Quebec on December 31, 2026. Second, your net tax owing also cleared that same threshold in 2025 or in 2024. Miss either condition and instalments are not required, no matter how large a single year's bill was.

The part that surprises most retirees: CPP and OAS are not taxed at source the way a paycheque is. Withholding on both is voluntary — you have to request it — so by default nothing is collected upfront. Stack that on top of a RRIF, and the math gets sharper still. The CRA-prescribed RRIF minimum withdrawal comes out with zero withholding tax by law, regardless of the RRIF's size or your bracket. A 75-year-old with a $500,000 RRIF has to withdraw $29,100 as the 2026 minimum, and none of it is collected in advance. Layer that on CPP and OAS income underneath it, and even at Ontario's lowest combined marginal rate — 19.05% on roughly the first $54,000 of taxable income — that single RRIF withdrawal alone works out to roughly $5,500 in federal-plus-provincial tax nobody withheld. Cross $3,000 two years running and instalments follow automatically. (For how the bracket layers stack, see our federal tax brackets guide.)

CRA is explicit about which income types create this gap: self-employment income, rental or investment income, certain pension payments, and income from more than one job. None of these route through an employer's payroll system, so none of them get the automatic deduction a T4 job does.

This is the same marginal-versus-average confusion that trips people up on the tax return itself — a retiree or consultant looks at their bracket and assumes withholding roughly covers it, when in practice nothing was withheld on the piece that matters most. See our breakdown of how Canadian marginal tax actually works if that distinction is not intuitive yet.

The 2026 Instalment Calendar — and Why September 15 Is Next

Most individuals required to pay instalments follow four fixed dates. When a due date lands on a weekend or a CRA-recognized holiday, CRA treats the payment as on time if it arrives the next business day — which is exactly what happened with the first 2026 date.

Two groups run on a different calendar entirely. If your main source of 2026 income is self-employment from farming or fishing, you skip the quarterly schedule and make a single payment by December 31, based on one reminder CRA mails in November rather than the usual February/August pair. And if someone required to pay instalments dies during the year, any instalment due on or after the date of death does not have to be paid — the estate is not billed for instalments the person never lived to owe.

How CRA Calculates What You Owe: 3 Methods

CRA sends instalment reminders (form INNS1) twice a year — a February reminder covering the March and June payments, and an August reminder covering September and December. If September 15 is the first instalment deadline you have ever had to think about — a first full year of RRIF withdrawals, a new consulting practice, a non-registered portfolio that started throwing off real income — an August-only reminder, with no February one before it, is usually why. You have three ways to calculate what you actually owe.

The prior-year and current-year totals both add estimated CPP contributions payable and voluntary EI premiums payable on top of net tax owing — the relevant add-on for anyone self-employed. Pay the full amount your chosen method calls for, by each due date, and CRA generally will not charge interest or a penalty, unless the estimate itself turns out to be too low.

What Skipping the September 15 Payment Actually Costs

Getting a reminder in the mail is not the same as owing money. If CRA sent you one but your real 2026 net tax owing will land at or under $3,000 ($1,800 in Quebec), you can disregard it entirely — no payment, no consequence. The cost only shows up if you genuinely owe instalments and pay late, short, or not at all.

Instalment interest compounds daily at CRA's prescribed rate — 7% annually for the July-to-September 2026 quarter, reset every three months. CRA calculates it as the interest you should have paid on each required instalment, from its due date to your balance-due date (April 30, 2027 for most individuals), minus any interest earned on what you actually paid. The result is only billed if it exceeds $25. Most taxpayers do not realize CRA runs this calculation three ways — under the no-calculation, prior-year, and current-year methods — and bills you based on whichever produces the smallest number. You get the benefit of the cheapest method automatically, without asking for it.

Put real numbers on it. Say a $3,500 instalment was due September 15 and you catch up when you make your December 15 payment instead — that is 91 days late, costing roughly $61 in interest at the current 7% rate. Ignore it completely and pay only when you file next April, and that stretches to 227 days — roughly $155 in interest on the same $3,500 if the rate held at 7%, on top of the $3,500 itself. Neither number is catastrophic on its own. The risk is what happens when several instalments run short across the year at once.

The Instalment Penalty — A Separate Charge Once Interest Tops $1,000

Interest and the instalment penalty are two different things, and conflating them understates how this can escalate. The penalty only applies once your total 2026 instalment interest charges exceed $1,000 for the year — a single late payment on a modest instalment rarely gets there. When it does, CRA takes the higher of two figures: a flat $1,000, or 25% of what your interest would have been had you made no instalment payments at all. That higher amount is subtracted from your actual interest charge, and the remainder is divided by two.

CRA's own published example shows the mechanics: a taxpayer with a $2,500 actual instalment interest charge for the year — against a hypothetical $3,200 if they had paid nothing at all — has 25% of that hypothetical ($800) compared to the flat $1,000. Since $1,000 is higher, CRA subtracts it from the $2,500 actual charge, leaving $1,500, then divides by two: a $750 instalment penalty, stacked on top of the $2,500 in interest, stacked on top of the tax that triggered it all.

How to Reduce or Eliminate Your Instalments Before September 15

If your circumstances changed enough that 2026 net tax owing will land at or under the threshold, you can simply stop paying and disregard future reminders. If you are still over it, three levers actually move the number. First, request extra withholding directly: OAS through Form ISP3520OAS, CPP through Form ISP3520CPP (Quebec Pension Plan benefits go through Retraite Québec instead), or an employer/pension plan through Form TD1. Self-employment, rental, investment, and capital gains income cannot have tax withheld at the source at all, no matter which form you file — those categories have to be managed through the instalment system itself, or through the estimate you choose under the current-year option. For the exact OAS and CPP amounts currently in pay, see our July 2026 benefit increases guide.

Second, an RRSP contribution before the deadline cuts net tax owing directly, not just the instalment estimate — the 2026 limit is $33,810 or 18% of prior-year earned income, whichever is lower. See our RRSP deadline strategies guide for the exact math on how much room you have left. Third, if you are due a refund on your 2025 return, you can direct CRA to apply it straight to your instalment account instead of taking it as cash, and CRA applies the full amount on the assessment date. Paying an instalment early or slightly over the required amount also earns instalment credit interest — not refundable, but usable against any shortfall interest for the same tax year, which is the cheapest insurance available if your income is genuinely uncertain heading into December.