The trigger is $3,000 of tax, tested against two years
Instalments become mandatory once total taxes payable pass $3,000, and the test looks at both the current year and the year before it. Under that line, nothing is required during the year and the full amount is simply paid on the balance-due day. Over it, the tax is meant to arrive in monthly or quarterly payments as the profit is earned, with only the remainder settled after year-end. Ontario corporate tax is administered by CRA and rides in the same payment, so one instalment covers both governments rather than two.
The balance-due day matters as much as the instalment schedule. Most corporations must pay any remaining balance two months after year-end. A Canadian-controlled private corporation that claimed the small business deduction, with taxable income within the limit for itself and its associated corporations, generally gets three months. The T2 return is not due until six months after year-end either way, which is exactly why so many owners meet their tax bill long after the moment they could have done anything about it.
First years are the quiet exception. Instalment interest is measured against the smallest of three permitted calculations, and two of those look backwards at tax paid in earlier years. A corporation in its first taxation year has no history behind it, so the backward-looking figures are nil and no instalment obligation effectively bites. The tax still comes; it just comes all at once on the balance-due day.
Monthly or quarterly: the test that sets your rhythm
Monthly is the default, and quarterly has to be earned. Monthly instalments are due on the last day of every month of the tax year. To pay quarterly instead, on the last day of each three-month period, a corporation has to be a CCPC that claimed the small business deduction in the current or previous year, have taxable income of $500,000 or less in the current or previous year together with its associated corporations, have taxable capital employed in Canada of $10 million or less across that same group, and have a perfect compliance record over the previous twelve months.
That last condition is the one that trips owner-managed businesses. Perfect means perfect: no late T2, no late GST/HST return or payment, no late payroll remittance, nothing outstanding on any account CRA administers. A single filing missed by a week during a busy season can cost the quarterly privilege and turn four payments a year into twelve. It is one of the few places in the tax system where administrative tidiness has an immediate cash value.
Two more mechanics are worth knowing. Instalments are calculated on tax payable, not on revenue or on the number the bookkeeper booked as an accrual, so the figure comes out of the tax return rather than the income statement. And unlike individuals, corporations do not receive reminders that compute the payment for them. CRA sends a statement of account; the calculation is yours to make, which means the first sign of a problem is often interest on a return filed months later.
Why the second profitable year is the one that hurts
The pain point is almost never the first good year, it is the one after. In year one, the balance is paid on the balance-due day with no instalments required. In year two, the corporation pays that balance and begins twelve monthly instalments on top of it, so a single cash cycle carries roughly two years of tax. Nothing has gone wrong and no rate has changed. The schedule simply caught up with the profit.
Three calculation methods exist: estimate the current year and pay a twelfth of it each month, pay a twelfth of last year tax, or use a hybrid that applies the year-before-last figure for the first two months and last year figure across the rest. Paying on last year figure is the safe harbour, because meeting it protects you from instalment interest even if this year turns out much better. Estimating is cheaper on cash flow when profit is falling, and expensive when your estimate proves optimistic. Interest on short instalments compounds daily at the prescribed rate for overdue amounts, it is not deductible, and once it grows past a threshold an additional penalty layers on top of it.
Instalments paid early earn offsetting credit that can absorb interest on later ones, so catching up in June is worth materially more than catching up in December. Here is what usually changes the number, and what to do about each:
| What changed in the business | What it does to instalments | The move |
|---|---|---|
| First profitable year | No instalments required now; the full obligation starts next year on top of this year balance | Reserve the balance and next year monthly amount out of the same profit |
| You stopped bonusing the profit out | Corporate taxable income rises, so tax and next year instalment base rise with it | Set the pay mix before year-end, not at filing time |
| Income crossed the small business limit | The excess is taxed at the general rate; the base jumps faster than revenue did | Model the limit across the associated group early in the year |
| Investment income grew inside the company | Refundable tax has to be funded through instalments even though it comes back later | Hold that cash rather than reinvesting the gross amount |
| A one-time gain on selling property or equipment | Last year tax is inflated, so instalments based on it badly overshoot | Switch to the current-year estimate, with support for the number |
| One late payroll or GST/HST remittance | Quarterly eligibility is lost; twelve payments replace four | Repair the compliance record before the next twelve-month window closes |
How you pay yourself sets next year instalment base
Owner compensation is the biggest lever on the instalment base, because salary and bonus are deductible to the corporation and dividends are not. A year of paying yourself in dividends leaves corporate taxable income intact, so corporate tax and the instalments that follow it stay high, while a bonus strips income out of the corporation and shrinks both. Neither is automatically better. A bonus creates payroll remittances during the year and personal tax instalments for you personally, so the same money is often just being pushed through a different meter.
Timing rules apply to the strip. A bonus accrued at year-end must actually be paid, with the source deductions remitted, within 180 days of the corporation year-end, or the deduction is denied and reversed into income. Owners who accrue a bonus to bring taxable income under the small business limit and then leave it unpaid discover the reversal two years later, at which point the instalment base was wrong all along.
Shareholder loans are the other blind spot. Drawing personally through the loan account moves cash out of the company without reducing its taxable income, so the corporation still owes tax on profit it no longer holds. Add a habit of running personal costs through the business, covered in can my corporation pay personal expenses, and a reassessment can raise tax for closed years and lift the instalment base for the open one at the same time. The decision framework for the whole picture sits in corporate tax planning for owner-managed businesses.
Passive income makes you fund a tax you get back later
Investment income earned inside a CCPC carries a combined rate around 50%, a large slice of which is refundable to the corporation only when it pays taxable dividends. Instalments do not care that the money comes back. The corporation has to fund the full amount during the year and wait for the dividend refund, so a portfolio that had a strong year quietly raises the payment schedule long before any of it is recovered. Portfolio dividends received from other corporations bring Part IV tax, which is generally settled at the balance-due day rather than spread across instalments, adding a second lump that the monthly schedule never signalled.
There is a compounding effect through the small business limit. Once aggregate investment income in the associated group passes $50,000 in a year, the business limit grinds down by $5 for every $1 of excess and disappears entirely at $150,000, pushing active income from the small business rate to the general rate. The tax increase shows up in the year it happens, and then again a year later in a higher instalment base. What counts as the active side of that line is set out in what is active business income.
What changes the answer, and how we handle it
Five facts decide what your corporation actually has to pay and when:
- Total tax payable in the current and prior year: both are tested, so one good year drags the obligation into the next one
- Small business deduction status: it sets the rate, the three-month balance-due day and quarterly eligibility all at once
- Your twelve-month compliance record: one late remittance anywhere converts quarterly into monthly
- The direction of profit: rising profit favours the prior-year safe harbour, falling profit favours a supportable current-year estimate
- Owner pay and investment income: the bonus decision and the passive-income grind both move the base a full year before you feel them
Our approach is unglamorous. We calculate the instalment schedule from the T2 as soon as the year is closed rather than at filing time, choose the calculation method deliberately for the direction the business is heading, and put the amounts on a calendar the owner and the bookkeeper both work from. Where profit is volatile we revisit the estimate mid-year, because an overshoot ties up cash and an undershoot compounds daily. This is routine work for a corporate tax planning CPA in Ontario, and it sits inside Tax Planning & Advisory next to the annual owner-pay decision.
If a large balance has already landed and the instalments start next month, deal with both at once rather than in sequence: the payment arrangement, the pay mix that lowers next year base, and the reserve that stops the cycle repeating. A free 15-minute discovery call is enough to size all three.
Source: CRA — Corporation payments.
