Who owes installments, how to calculate them, and how to avoid CRA interest — explained clearly for self-employed Canadians and investors.
Quarterly tax installments are pre-payments of income tax that the CRA requires from certain Canadians — mainly the self-employed, retirees with pension income, and investors with significant investment income. Unlike employees who have tax withheld automatically each paycheque, these taxpayers must proactively send money to the CRA four times per year. Missing installments or underpaying results in interest charges at the CRA's prescribed rate.
The CRA requires installment payments if your "net tax owing" exceeds $3,000 in the current year AND it exceeded $3,000 in either of the two preceding years. Net tax owing = federal + provincial taxes + CPP (self-employed) minus any tax withheld at source. Residents of Quebec use a $1,800 threshold for federal and a separate provincial threshold.
Common groups required to pay installments:
The CRA offers three methods for calculating installments. You can use any one — the goal is to avoid interest by paying enough:
Pay 25% of your estimated net tax owing for the current year each quarter. This is the most accurate if your income is consistent or you can estimate it well. Risk: if you underestimate, you'll owe interest on underpaid amounts.
Pay 25% of last year's net tax owing each quarter. Simple to calculate and completely eliminates interest risk if you pay the full prior-year amount — even if you owe more at filing time.
Pay 25% of two years ago's tax in Q1 and Q2, then adjust based on last year's tax in Q3 and Q4. This is the method the CRA actually uses in its installment reminder notices.
The CRA sends installment reminders in February and August. These are not optional bills — they're suggestions based on the two-year-prior method. You can ignore the amounts and use a different method, but you cannot ignore the obligation to pay if you meet the $3,000 threshold.
If you didn't receive a reminder, you're still required to pay if you meet the threshold. Check CRA My Account online to see your installment history and any amounts owing.
The CRA charges interest at the prescribed rate (currently around 9–10%) on late or underpaid installments. Interest is calculated daily from the due date. If your installment interest exceeds $1,000, the CRA may also charge a penalty of 50% of the interest over $1,000.
However, if you overpay installments, the CRA pays you interest at the same rate on the overpayment — though this is rarely a good strategy.
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