A letter from CRA arrives in the mail. It requests a payment you were not expecting, for an amount you do not fully understand, with a due date that has already passed. For many self-employed Canadians, that letter is how they first learn quarterly instalments exist.
Instalments are not a penalty or an audit signal. They are CRA’s mechanism for collecting income tax throughout the year from people who do not have an employer withholding tax on their behalf. Understanding how they work, when they are required, and how to calculate them correctly avoids both the surprise and the interest charges that come with getting it wrong.
Key CRA References
Required tax instalments for individuals | Who has to pay instalments | Options to calculate instalment payments | Instalment payment due dates | Interest and penalty charges
What Instalments Actually Are
Employees have tax withheld from each paycheque. The employer remits that tax to CRA on their behalf throughout the year. Self-employed individuals have no employer doing this. Their net income is earned with no tax withheld, which means the full tax owing is due at filing time unless instalments are paid during the year.
CRA uses instalments to approximate what a salaried employee’s withholding would look like. Rather than waiting until April 30 to collect the full amount, CRA requires quarterly payments on March 15, June 15, September 15, and December 15 of the tax year. These payments reduce your balance owing at tax time and, if paid in the required amounts by the due dates CRA publishes, can eliminate instalment interest.
Instalments are advance payments on the current year’s tax liability. They are not a separate tax. If you overpay through instalments, the excess is refunded when you file.
When CRA Requires Instalments
Not every self-employed person is required to pay instalments. CRA requires instalment payments when net tax owing exceeds CAD $3,000 in the current year and in either of the two preceding years. For instalment purposes, the required calculation can also take into account CPP contributions payable and voluntary EI premiums. The CAD $3,000 threshold applies federally. Quebec uses a separate threshold of CAD $1,800 for provincial purposes.
If your self-employment income is new, or if your income dropped significantly in a prior year, you may not be required to make instalments even if your current year income will be high. The triggering condition requires the threshold to be exceeded in the current year and at least one of the two prior years.
CRA often sends instalment reminders to people who will likely have to pay, but your legal obligation is determined by the rules, not by whether a reminder arrives. If you have been self-employed for two or more years and your net tax owing has exceeded CAD $3,000 in those years, it is worth confirming whether instalments are required for the current year.
The Three Calculation Methods
CRA permits three methods for calculating instalment amounts. Each produces a different number. The method you choose affects your cash flow during the year and your exposure to instalment interest if you underpay. The CRA page on options to calculate your instalment payments explains all three in full.
No-calculation method (CRA’s reminder amounts)
CRA sends instalment reminders in February and August showing the amounts to pay. The no-calculation method uses those reminder amounts exactly as shown. If you pay the CRA reminder amounts in full and on time, CRA will not charge instalment interest or a penalty under the no-calculation option, even if you still have a balance owing when you file. If your income is lower than prior years, you may overpay during the year and receive a refund at filing.
Prior-year method
Pay instalments equal to your total net tax owing from the prior year, distributed across the quarterly payment dates. This method also qualifies for the safe harbour from instalment interest, meaning CRA will not charge instalment interest even if the payments are lower than your actual current year tax.
This is the simplest self-calculated alternative when CRA reminders are not available or when you prefer to work from your prior year return independently. CRA publishes a calculation chart for instalment payments that walks through this method step by step.
Current-year method
Estimate your current year net income and calculate your estimated tax liability based on that estimate. Pay quarterly instalments equal to a portion of that estimated amount across the due dates. This method aligns your payments most closely with your actual current year obligation.
The risk with the current-year method is estimation error. If your actual income is higher than your estimate, you will have underpaid and CRA will charge instalment interest on the shortfall. If your estimate is accurate or conservative, this method minimises the overpayment that the prior-year method can produce in a declining income year.
A Worked Example: How the Calculation Works
Take a mortgage agent with the following situation: CAD $95,000 net self-employment income in the prior year, with total federal and provincial tax plus CPP contributions of CAD $38,000. In the current year, their income is expected to be approximately the same.
Using the prior-year method, the total instalment amount for the year is CAD $38,000. CRA’s calculation chart and reminder system determine how that amount is allocated across the March 15, June 15, September 15, and December 15 payment dates. If the agent pays the required amounts on each of those dates, paying the full prior-year instalments on time generally protects against instalment interest. Any remaining balance owing at year end is still due by April 30, and any overpayment is refunded when the return is filed.
If the same agent expects their current year income to increase to CAD $130,000, they might prefer the current-year method to avoid a large lump sum payment at filing. They would estimate their tax and CPP for the higher income year and pay accordingly. The trade-off is the estimation risk: if the actual income comes in higher than estimated, instalment interest applies on the shortfall.
What Happens If You Miss an Instalment
Missing a quarterly instalment does not automatically trigger a penalty. CRA charges instalment interest on late or insufficient payments, compounded daily at the prescribed interest rate, which changes quarterly. Instalment interest is not deductible. It is charged on the amount that was underpaid and for the period it was underpaid, not on the full annual amount.
CRA also charges a late instalment penalty in addition to interest if your instalment interest for the year exceeds CAD $1,000. The penalty is 50% of the excess above the greater of CAD $1,000 or 25% of the instalment interest that would have been charged if no instalments were made. In practice, this penalty compounds the cost of significant underpayment.
The safe harbour provisions under the prior-year method and the no-calculation method exist precisely because they eliminate instalment interest regardless of whether your current year tax ends up higher. Paying these amounts in full and on time protects against interest even in a high-income year.
Where Instalments Get Complicated
The straightforward case assumes a single source of self-employment income with predictable timing. Several situations make the calculation and timing more complicated.
Irregular income years create difficulty with the current-year method because the income estimate is unreliable until late in the year. A real estate agent who closes a large transaction in November cannot easily estimate December income in March. Using the prior-year method avoids the estimation problem at the cost of potentially overpaying if the current year is weaker.
Mixed income situations, where a person has both employment income with withholding and self-employment income, require attention to how much tax is already being remitted through payroll. Only the net tax owing after accounting for withholding counts toward the CAD $3,000 threshold. An IT contractor who also has a part-time employment position may have less instalment exposure than their self-employment income alone would suggest.
Income that arrives unevenly during the year affects cash flow even when the annual instalment amount is calculated correctly. Quarterly instalments are fixed regardless of when income is earned. A mortgage agent whose commissions are concentrated in spring and fall still owes the March 15 instalment even if January and February were slow.
The interaction between instalments and RRSP contributions is worth understanding. RRSP contributions made in the first 60 days of the year reduce net income for the prior year’s return but do not affect the instalment calculation for the current year in progress. The deduction affects next year’s instalment base, not the current one.
The Practical Question to Ask
If you have been self-employed for more than two years and your net tax owing has exceeded CAD $3,000 in those years, the question is not whether instalments apply but which method works best for your income pattern.
The no-calculation method is the lowest-effort approach: it uses CRA’s reminder amounts directly and protects against instalment interest and penalty if paid in full and on time. The prior-year method is the simplest self-calculated alternative when you want to work from last year’s return independently. The cost of both approaches is the potential overpayment in years when income declines. The current-year method requires an estimate that needs to be revisited each quarter as the year develops, and carries interest risk if the estimate is too low.
Self-employed Canadians face instalment obligations for both federal income tax and, in most provinces, provincial income tax, as well as CPP contributions on self-employment income. CPP contributions on self-employment income are calculated at the time of filing but affect the net tax owing amount that determines whether the instalment threshold is met. CRA’s guidance on interest and penalty charges is the primary reference for understanding the cost of getting this wrong.
If you are not certain whether instalments apply to your situation, or which method to use, that is a calculation worth running before the March 15 date arrives. Getting the method wrong does not typically produce catastrophic results, but instalment interest and late penalties accumulate in ways that are avoidable. See our guide to CRA penalties and interest for more on how these charges are calculated.
Email contact@teplov.ca or visit our 2025 Tax Return Services page to get in touch.