T2 Adjustment Request Calculator
A corporation that missed a deduction has three years from the date of its original notice of assessment to have the year reassessed, four years if it is not a Canadian-controlled private corporation, and no equivalent second chance once that window closes. Work out whether the year is still open, what the adjustment actually recovers after the fee, and whether an adjustment request or a voluntary disclosure is the correct route.
net after the fee
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Where the Year Stands
| Item | Basis | Result |
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What the Adjustment Is Worth
| Item | Basis | Amount |
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Adjustment Request Against the Other Routes
| Feature | Adjustment Request | Voluntary Disclosure | Notice of Objection |
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Points That Decide This
What to Do Next
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Disclaimer: Subsection 152(3.1) of the Income Tax Act fixes the normal reassessment period at three years after the day of sending of the original notice of assessment for a Canadian-controlled private corporation and four years for any other corporation, and subsection 152(4) permits the Minister to reassess within that period on a taxpayer request. Subsection 152(4.2), which allows the Minister to reassess a statute-barred year in order to give a refund, applies only to an individual other than a trust and to a graduated rate estate, so it is not available to a corporation. Paragraph 152(4)(b)(i) allows a reassessment within an extended period to give effect to a loss carryback, and paragraph 152(4)(a)(i) removes the time limit entirely where there has been a misrepresentation attributable to neglect, carelessness or wilful default, so the period protects the corporation less than it protects the Minister. Capital cost allowance is a permissive deduction claimed under paragraph 20(1)(a) and Part XI of the Regulations, and the CRA’s administrative position on revising a permissive deduction after filing is set out in Information Circular IC84-1, under which a revision that amounts to retroactive tax planning is generally refused. The prescribed information for a scientific research and experimental development claim must be filed within the period in subsection 37(11), which is twelve months after the filing-due date for the year, and that deadline cannot be extended. Refund interest is paid under subsection 164(3) from a date fixed by that subsection rather than from the day the tax was paid, and arrears interest is charged under subsection 161(1); the prescribed rates are set quarterly under section 4301 of the Income Tax Regulations. The Voluntary Disclosures Program is an administrative program operated under the taxpayer relief provisions in subsection 220(3.1), and a disclosure is generally not accepted as voluntary once the CRA has contacted the corporation about the matter. The rates, fees, interest periods and dates used here are inputs that should be replaced with the corporation’s own assessed figures and the current published rates before anything is relied on. This page is general information, not tax advice.
Three Years for a CCPC, Four for Everyone Else
The question of how to amend a corporate tax return in Canada starts with one date, and it is not the filing date. Subsection 152(3.1) measures the normal reassessment period from the day the CRA sent the original notice of assessment for that year. For a Canadian-controlled private corporation the period is three years from that day. For any other corporation, including a public corporation and a corporation controlled by non-residents, it is four years.
Getting this wrong by a single year is the most expensive mistake available on this subject, because the consequence is not a penalty but a permanently lost deduction. A corporation that assumes four years when it only has three will send an adjustment request that the CRA has no power to act on.
Two details are worth holding onto. The clock runs from the original assessment, so a later reassessment for some other reason does not restart it. And it runs from the date of sending, which is the date printed on the notice, not the date the corporation opened the envelope.
The period cuts both ways, but not evenly. Inside it, the corporation can ask for a change and the CRA can make one. Outside it, the corporation’s request is generally out of time, while paragraph 152(4)(a)(i) still allows the Minister to reassess without any time limit where there has been a misrepresentation attributable to neglect, carelessness or wilful default. The corporation’s window closes first.
The Warning That Matters Most: A Corporation Has No Ten-Year Relief
Individuals who miss a deduction have a safety net. Subsection 152(4.2) lets the Minister reassess a statute-barred year in order to reduce tax or give a refund, on request, going back ten calendar years. It is the provision behind every article about the ten-year rule for adjusting old returns.
It does not apply to corporations. By its own terms subsection 152(4.2) applies to an individual other than a trust and to a graduated rate estate. There is no corporate equivalent. Once a corporation’s normal reassessment period closes on a year, a deduction it forgot to claim in that year is generally gone for good, and no relief application, fairness request or taxpayer relief claim brings it back.
This is the single most misunderstood point on the subject. Advisers and online guidance routinely transplant the ten-year individual rule onto corporations. Please do not plan on the basis of it. A corporation asking about a corporate tax refund from amending prior years has three or four years from each notice of assessment and then nothing.
The picture is not entirely bleak, and two genuine exceptions matter. Paragraph 152(4)(b)(i) allows a prior year to be reassessed within an extended period specifically to give effect to a loss carryback, so a loss can still reach a year that is otherwise closed to amendment. And a loss, an undepreciated capital cost balance or any other pool the corporation failed to use is not destroyed by the closing of a year; it simply carries forward and can be claimed in a year that is still open. What is lost is the refund of tax already paid in the closed year, not the underlying pool.
SR&ED Has an Eighteen Month Wall
Scientific research and experimental development is the one item on the list where the reassessment period is beside the point. Subsection 37(11) requires the prescribed claim information to be filed no later than twelve months after the filing-due date for the year. A corporation’s filing-due date is six months after its year end, so in practice the deadline is eighteen months after the year end.
That deadline is statutory and it cannot be extended. It is not subject to taxpayer relief, it is not subject to the CRA’s discretion, and it is not rescued by the year still being inside the normal reassessment period. A corporation with a December year end that has not filed its SR&ED claim by the end of the following June, eighteen months later, has lost the claim even though the year remains open for every other kind of adjustment.
| Year End | Filing Due Date | SR&ED Reporting Deadline | Extendable |
|---|---|---|---|
| 31 December | 30 June the following year | 30 June, two years after the year end | No |
| 31 March | 30 September the same year | 30 September, the year after | No |
| 31 July | 31 January the following year | 31 January, two years after | No |
The calculator computes this date from the year end entered and flags it whenever the SR&ED option is selected, because it is the one deadline on this page that can already have passed while everything else still looks comfortable.
A Missed CCA Claim Is Not Automatically Fixable
Capital cost allowance is a permissive deduction. Paragraph 20(1)(a) allows the corporation to deduct such amount as is allowed by regulation, and the Regulations set a maximum rather than a required amount. A corporation that claimed nothing has not made an error; it has made a choice, and the undepreciated capital cost simply stays in the class.
That is why a missed CCA claim for a prior year of a corporation sits in a different category from a forgotten invoice. The CRA’s administrative policy on revising a permissive deduction after a return has been filed is set out in Information Circular IC84-1, and the policy will generally not allow a revision where the effect is retroactive tax planning. If the year is being revisited only because the rate has since changed, or because a loss has appeared that makes the deduction more valuable now, expect the request to be refused.
Where a revised CCA claim tends to succeed. The strongest cases are where the original figure was simply wrong rather than chosen: an asset left off the schedule, a class applied incorrectly, a half-year rule misapplied, or an addition posted to the wrong year. The weakest cases are where the original claim was deliberate and the corporation has since changed its mind.
The practical consequence is usually better than it first looks. Undepreciated capital cost is not lost when a year closes. If the CRA refuses to revise the prior year, the balance remains in the class and the deduction can be taken in an open year instead. The corporation loses the timing, not the deduction.
How the Request Is Actually Made
There is no single answer to whether you can refile a T2 after assessment, because what the corporation sends is not a fresh return. It is a request to reassess a specific year, and it has to be presented as one.
| Route | How It Works | Typical Use |
|---|---|---|
| T2 Adjustment Request form | Paper request identifying the year, the lines changed and the reason | One or two discrete changes with documents attached |
| Amended return through certified software | The return is refiled electronically and flagged as an amendment | Changes that ripple through several schedules |
| Represent a Client | The authorised representative submits the change online | Straightforward numeric changes with no attachments |
Whichever route is used, the submission should identify the tax year end, the specific lines and schedules being changed, the amount of each change, and a short explanation of why the original figure was wrong. Attach what supports it: invoices, a corrected capital asset schedule, a revised Schedule 8, a revised Schedule 1 reconciliation. A request that arrives without a reason is the one that comes back with questions.
Please do not simply file a whole new T2 without flagging it as an amendment. An unflagged second return for a year already assessed causes duplicate processing, and the CRA’s usual response is to reject it or hold it, which wastes weeks of a deadline that may be short. If the corporation is behind on filings altogether rather than correcting one year, the corporate tax cleanup is the right starting point, because the amendment can only be assessed once the underlying years exist.
Adjustment Request or Voluntary Disclosure
These two routes are confused constantly and the distinction is genuine. If you forgot to claim expenses on your T2, taxable income goes down, there is no penalty in prospect, and the correct route is an ordinary adjustment request. The Voluntary Disclosures Program is not needed and applying through it only slows the file down.
The VDP exists for the opposite case: an omission that would attract a penalty if the CRA found it first. Unreported income, an unfiled information return, an unreported foreign holding. There the programme offers relief from penalties and partial relief from interest in exchange for coming forward.
| What Changed | Effect on Taxable Income | Correct Route |
|---|---|---|
| Expenses, CCA or losses not claimed | Down | Adjustment request |
| Small business deduction claimed wrongly in the corporation’s favour | Up | Adjustment request, expect interest |
| Revenue omitted from the return | Up | Voluntary disclosure |
| Information return never filed | Neutral | Voluntary disclosure |
The timing rule is what makes the choice urgent. A disclosure is only accepted as voluntary if the corporation comes forward before the CRA does. Once the CRA has begun an audit, issued a query about the matter, or otherwise made contact, voluntariness is generally lost and the relief goes with it. That is what the CRA status question in the calculator drives, and it is why a corporation that suspects unreported income should not wait to see whether anything comes of a letter.
What Changing One Year Does to the Years After It
An adjustment almost never stops at the year it is made in. Reducing taxable income in one year changes the loss balance carried out of it. Claiming capital cost allowance changes the undepreciated capital cost carried into the next year, which changes the maximum claim there, and the year after that. A corrected small business deduction can change a pool balance or a credit carryforward.
So the later returns that have already been filed on the old numbers may themselves need amending, and each of those years has its own reassessment deadline running from its own notice of assessment. The calculator prices this as a flagged consequence rather than an afterthought, because a request that fixes one year and leaves three inconsistent ones behind invites questions the corporation does not want.
One useful consequence of the cascade is that it is often possible to get most of the benefit without touching a closed year at all. Where the oldest year is out of time, the pool or loss it generated is usually still available and can be claimed in the earliest year that remains open. The reassessment period checker will show which of the corporation’s years those are.
What This Calculator Does Not Cover
- Objections and appeals, which are a different remedy with their own timetable. A notice of objection must be filed within ninety days of the notice of assessment or reassessment being sent, and is the route where the corporation disagrees with what the CRA has decided rather than with its own return
- Waivers on form T2029, which end or limit a waiver of the normal reassessment period, and the effect of a waiver already given
- Amended and late-filed elections, including elections that can be made late or amended under subsection 220(3.2) and the prescribed penalty that goes with them
- GST and HST adjustments, which run on their own limitation periods and their own correction mechanics under the Excise Tax Act
- Provincial-only changes, including Ontario credits and returns administered separately from the T2
- Transfer pricing adjustments and the penalty in section 247, where documentation and contemporaneous records govern the outcome
- Gross negligence and repeated failure penalties, which change the arithmetic entirely where income was omitted
- Acquisition of control, amalgamations and wind-ups, which restrict what a loss or pool can still be used against
The deadline is the part that cannot be recovered. If a year is close to its three or four year mark, please deal with it first and refine the numbers afterwards. Our corporate tax cleanup work covers the adjustment request, the knock-on years and the reassessments that follow, and the notice of objection deadline calculator covers the position where the corporation is disputing an assessment rather than correcting one.
Frequently Asked Questions
Amending a filed T2, the reassessment deadline and what the CRA will allow.
Related Calculators and Guides
More tools for correcting, reassessing and disputing a corporate year.
A Missed Deduction Is Recoverable Until the Year Closes
Send us the notice of assessment for the year and what was missed. We will confirm whether the year is still open, prepare the adjustment request with the supporting schedules, amend the later years it affects, and follow the reassessment through to the refund.