For an Ontario corporation with a December 31, 2026 year-end, the key dates are: T4 slips by March 1, 2027, the tax balance by March 1 (or March 31 for most small CCPCs), and the T2 return and Ontario annual return by June 30, 2027. Miss the balance date and interest starts, even if the T2 is on time.
November is the right month to sort this out. Most owners with a calendar year-end have about eight weeks left in the year, and the first deadline after December 31 arrives sooner than people expect. This is the calendar, the rules behind it, and what to do before the holidays.
Ontario corporate tax deadlines at a glance (December 31 year-end)
| What | Rule | Date for a Dec 31, 2026 year-end |
|---|---|---|
| T4 slips and summary | Last day of February | Mon, March 1, 2027 (Feb 28 is a Sunday) |
| Corporate tax balance (general) | 2 months after year-end | Mon, March 1, 2027 |
| Corporate tax balance (most small CCPCs) | 3 months after year-end | Wed, March 31, 2027 |
| T2 corporation income tax return | 6 months after year-end | Wed, June 30, 2027 |
| Ontario annual return | Within 6 months after year-end | By June 30, 2027 |
If your year-end is not December 31, slide every line by the same number of months. The rules are below.
When is the T2 corporate tax return due?
CRA's rule is simple: file the T2 no later than six months after the end of each tax year. If the tax year does not end on the last day of a month, the return is due on the same day six months later. If the due date lands on a Saturday, Sunday or public holiday, CRA treats the return as on time if it is filed the next business day.
Two things catch new owners:
- No income is not an exemption. CRA says every resident corporation files a T2 every year, even with no tax payable. That includes inactive corporations and non-profits. Registered charities are one of the few exceptions.
- The T2 date is not the payment date. Paying in June because the return is due in June is how most first-year interest charges happen.
When is corporate tax payment due? The balance-due day
CRA calls it the balance-due day. Generally it is two months after the end of the tax year. It stretches to three months if all of these are true:
- the corporation was a Canadian-controlled private corporation (CCPC) throughout the year;
- it claimed the small business deduction for the year (or the prior year); and
- its taxable income was under the business limit.
Most owner-operated Markham corporations meet that test, which is why March 31 is the date many accountants circle. Check with yours before you count on it. If you do not qualify, the payment date for a December 31 year-end falls on Sunday, February 28, which moves to Monday, March 1, 2027.
First-year corporations have one break: CRA's instalment guide says a new corporation does not pay instalments in its first tax year. From year two, instalments may apply (eligible small CCPCs can pay quarterly). Budget for the year-one balance as one lump sum.
When are T4 slips due in 2027?
If the corporation paid salary in 2026 (including to you), the T4 slips and T4 Summary are due the last day of February. Because February 28, 2027 is a Sunday, that is Monday, March 1, 2027.
The penalty for late slips to employees is $25 a day per slip, minimum $100, maximum $2,500 per slip. For a two-person payroll, a week's delay costs more than an accountant's hour.
If you paid yourself only dividends, ask your accountant which slips apply. We have not listed T5 dates here.
Ontario annual return deadline
Ontario corporations file the annual return through the Ontario Business Registry, within six months after the end of each tax year. There is no government fee. Since May 5, 2021, CRA no longer accepts it with the T2, so this is a separate filing you have to remember.
Two other Ontario dates are not annual but still matter:
- Initial return: within 60 days of incorporating.
- Notice of change: within 15 days when directors, officers or the registered office address change.
If you moved this year and never updated the registry, fix it now: file a notice of change on the Ontario Business Registry before the annual return.
Watch your CRA mail: online mail is now the default
Since May 2025, CRA sends most business correspondence through online mail in My Business Account by default. CRA treats that mail as received on the date it is posted, not the date you log in. Set up the email notification and make sure it goes to an inbox someone reads.
Paper still arrives too: bank letters, Ontario notices, cheques. If the registered office is a home you are about to leave, or a unit nobody checks over the holidays, that is a gap. If you are changing addresses, this guide to updating CRA walks through it.
A November checklist for owners
- Confirm your year-end on your last T2 or Notice of Assessment. Do not assume December 31.
- Ask your accountant whether you get the three-month balance-due day.
- Set aside the tax now. Estimate it if you have to.
- Book payroll year-end so T4s go out before March 1.
- Check the Ontario Business Registry: registered office, directors, email for notices.
- Turn on CRA online-mail notifications for the right person.
- Put June 30, 2027 in the calendar for both the T2 and the annual return.
Where Markham Office fits
We do the corporate housekeeping, not the tax return. Annual return filing is $99 + HST, and an amendment is $119–$339 incl. any Ontario fee, + HST on our fee. A virtual office from $49/month gives the corporation a staffed registered address at 1005-3601 Highway 7 E., with letter mail handled while you are away for the holidays. For everything on the corporate side, start at Register, or call (905) 305-7800.