The 18-month filing deadline for SR&ED is one of the hardest rules in the Canadian tax system. There is no extension, no late-filing penalty regime, and no CRA discretion to accept a claim filed after the window closes. The deadline simply ends your right to claim the credit for that year.
Despite this, many Canadian companies miss it — either because they didn’t know the deadline existed, because they assumed their accountant was handling it, or because they started the process too late to complete it in time. Understanding exactly how the rule works is the first step to making sure it never applies to you.
The exact rule
SR&ED claims must be filed within 18 months of the end of the fiscal year in which the qualifying work occurred. For a company with a December 31 fiscal year-end, the work done in the 2024 fiscal year must be claimed no later than June 30, 2026. The claim is filed on Form T661, attached to your T2 corporate income tax return or as an amended T2.
The 18-month window is a statutory deadline under the Income Tax Act. CRA has no authority to grant extensions, regardless of the circumstances — illness, missed communication with your accountant, or a business disruption that delayed filing. The deadline is absolute.
💡 The most common missed-deadline scenario: a company hires an SR&ED consultant after hearing about the program, only to discover their most recent fiscal year already passed the 18-month window two months earlier. The work was fully eligible. The credit is permanently gone.
What CRA can and cannot do
CRA cannot accept a late T661. Even if you filed your T2 on time but forgot to attach the SR&ED schedules, you cannot add them afterward once the 18-month window has closed. There is a taxpayer relief provision (formerly called “fairness”) that allows CRA to waive some penalties and interest under certain conditions — but it does not extend to SR&ED filing deadlines. The deadline is jurisdictional, not discretionary.
What CRA can do: accept an amended T661 within the 18-month window if you filed an initial claim and need to correct or expand it. Corrections and additions to an already-filed claim are permissible up to the deadline.
Partial years and mid-year fiscal changes
If your company changed its fiscal year-end, the 18-month clock runs from the end of each tax year, including stub periods. A company that moves from a June 30 year-end to a December 31 year-end will have two deadlines in a short span — one for the stub period and one for the new fiscal year. Missing either window forfeits the credit for that period.
What to do if you’re approaching the deadline
- File something — even an incomplete claim filed on time can be amended later within the window. A filed claim preserves your right to the credit; an unfiled claim does not.
- Engage an SR&ED consultant immediately if you’re within 60 days of your 18-month deadline. Most consultants can prepare a baseline claim quickly if the work is clearly eligible.
- Talk to your accountant now about your SR&ED calendar for the current fiscal year. Set the deadline as a hard date in your financial planning calendar.
Protecting future claims
The single most effective protection against a missed SR&ED deadline is treating the filing window as a hard business deadline — like a GST remittance or a payroll tax date — not as a flexible goal. Build the SR&ED timeline into your fiscal year calendar in Q1, assign clear ownership, and engage your consultant well before the deadline, not after.
