Every corporation in Canada must file its T2 income tax return within six months of the end of its tax year, which puts June 30, 2026 as the T2 filing deadline for the large number of Toronto-area corporations with a December 31, 2025 fiscal year-end. This year the deadline carries extra weight: it falls exactly one day before Ontario's small business corporate income tax rate drops from 3.2% to 2.2% on July 1, 2026. A corporation filing its 2025 T2 this month is closing out the last full year taxed entirely at the old rate, while its 2026 fiscal year — already three months underway for a December year-end — is about to start prorating between the two rates. This piece covers the filing deadline itself, and the specific instalment and bookkeeping checks worth running now, before July 1, rather than discovering the rate change in next spring's filing.
Source: Government of Canada — When to file your corporation income tax return.
The six-month rule, precisely
The CRA's filing rule has two forms depending on whether the tax year ends on the last day of a month:
- If the tax year ends on the last day of a month, the T2 is due on the last day of the sixth month after that.
- If the tax year does not end on the last day of a month, the T2 is due on the same calendar day of the sixth month after that.
For a December 31, 2025 year-end, six months later is June 30, 2026 — a Tuesday, so no weekend adjustment applies this year. For an off-calendar year-end, the same-day rule applies instead: a March 15, 2026 year-end has a September 15, 2026 filing deadline. When a calculated due date does land on a Saturday, Sunday, or public holiday, the CRA treats the return as on time if filed the next business day.
Filing deadline vs. payment deadline
As with the personal T1, the T2 filing deadline is not the payment deadline. The CRA calls the payment date a corporation's "balance-due day," and for most corporations it falls well before the six-month filing deadline — the return itself reports and reconciles instalments already paid rather than triggering the tax bill on its own.
Source: Government of Canada — Balance due when filing a return: Corporate income tax payments.
A corporation can file its T2 perfectly on time by June 30 and still owe CRA arrears interest, because the balance-due day fell earlier in the year — well before the return was close to finished. Filing on time and paying on time are separate obligations on separate clocks; confirm your corporation's specific balance-due day with your accountant rather than assuming it lines up with June 30.
What's different about this June: the rate cut is three weeks away, not three months in the past
Ontario's small business corporate income tax rate falls from 3.2% to 2.2% on July 1, 2026, and the change is prorated for any tax year that straddles that date — the old 3.2% rate applies to the portion of a tax year before July 1, the new 2.2% rate to the portion on or after, weighted by days in each period.
For a December 31 year-end corporation, that means two very different things happening at once this month:
| Fiscal year | Rate treatment | Status as of June 21, 2026 |
|---|---|---|
| 2025 (Jan 1–Dec 31, 2025) | Flat 3.2% Ontario small business rate — no proration | T2 due June 30, 2026, being finalized now |
| 2026 (Jan 1–Dec 31, 2026) | Prorated: 3.2% for Jan 1–Jun 30, 2.2% for Jul 1–Dec 31 | In progress; roughly half already elapsed at the old rate |
The 2025 T2 due June 30 is unaffected by the rate cut — that year closes entirely under the old 3.2% rate. The proration only touches the 2026 fiscal year, which for a calendar-year corporation is already half over by the time July 1 arrives. That is the detail worth acting on now: instalments for the second half of 2026 should reflect the lower 2.2% rate on the post-July-1 portion of income, and a bookkeeping system that has not been told to prorate will keep calculating the whole year at the old rate through December.
What Toronto-area corporations should check before July 1
- File the 2025 T2 by June 30, 2026 if your year-end is December 31 — this return is unaffected by the rate cut and should not wait on it.
- Confirm your balance-due day for the 2025 filing separately from the June 30 filing deadline, especially if a payment is still outstanding.
- Ask specifically how your bookkeeping or payroll provider plans to prorate the 2026 rate cut, rather than assuming it will apply automatically at year-end. See our Ontario corporate tax guide for how the small business rate interacts with your T2 filing.
- Revisit remaining 2026 instalments now, before the July 1 split takes effect, so the second half of the year is not overpaid at the old rate. Model both halves of the year with our corporate tax calculator.
- Check whether the $600,000 Ontario small business limit (in effect since January 1, 2026) already changes how much of your 2026 income qualifies, independent of the July rate change — see our small business deduction limit guide.
- If you're incorporating a new business or restructuring an existing one this summer, factor the July 1 timing into when the corporation's own first fiscal year should start; see our guide to incorporating a business in Ontario.
Why acting before July 1 is different from reacting after
A corporation that waits until its 2026 T2 is being prepared next spring to think about the proration is choosing to find out, after the fact, whether its instalments through the second half of 2026 were calculated correctly. A corporation that checks now — while there are still more than three months of the fiscal year ahead of the split — has time to adjust remaining instalment payments, confirm the bookkeeping software is set up to prorate rather than apply a flat rate, and avoid either an instalment shortfall or an unnecessary overpayment sitting with the CRA until refunded next year. For a Toronto CCPC with a December year-end, this month's T2 filing and next month's rate change are two separate events that happen to land three weeks apart — worth treating as two separate to-do items rather than one.
Key takeaways
- Corporations with a December 31, 2025 year-end must file their T2 by June 30, 2026 — a Tuesday, no weekend shift.
- The filing deadline is not the payment deadline — confirm your corporation's balance-due day separately.
- Ontario's small business rate falls from 3.2% to 2.2% on July 1, 2026, prorated by days for any 2026 fiscal year that straddles that date.
- The 2025 T2 being filed this month is unaffected by the rate cut; the proration applies only to the 2026 fiscal year, already half elapsed.
- Checking instalments and bookkeeping settings before July 1 avoids finding out about a proration error only when next spring's T2 is prepared.
If your Toronto corporation's June 30 T2 filing, instalment planning, or bookkeeping setup needs a check before the July 1 rate change takes effect, RN Canada works with Ontario CCPCs remotely from our Edmonton and Vancouver offices through our tax return preparation services.