Corporate Loss Carryback Calculator
A non-capital loss can go back three years against tax the corporation has already paid, and whatever is left carries forward twenty. Work out the best allocation across the three prior years, the refund it produces, and what remains with its expiry year.
refund plus interest
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The Carryback Allocation, Year by Year
| Year | Taxable Income | Effective Rate | Loss Applied | Tax Recovered |
|---|
What Comes Back and What Is Left
| Item | Basis | Amount |
|---|
Carrying Back Now Against Carrying Forward Instead
| Feature | Carry Back Three Years | Carry Forward |
|---|
Points That Decide This
What to Do Next
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Disclaimer: A corporation’s non-capital loss is deductible under paragraph 111(1)(a) of the Income Tax Act in computing taxable income of the three preceding and, for losses arising in tax years ending after 2005, the twenty following tax years. A net capital loss is deductible under paragraph 111(1)(b) against taxable capital gains of the three preceding years and may be carried forward indefinitely, subject to the adjustment in subsection 111(1.1). The application is reported on Schedule 4, Corporation Loss Continuity and Application, and a request to carry a loss back to a prior year is made with the loss-year return or separately once that return has been filed. Subsection 152(4)(b)(i) permits the Minister to reassess a prior year beyond the normal reassessment period to give effect to a loss carryback, within an extended period, so a request made too late can be refused even though the loss is real. For interest purposes, subsection 161(7) generally requires the prior year’s tax to be computed without regard to the carryback until a date tied to the loss year, so a carryback does not eliminate arrears interest that accrued before that date, and subsection 164(5) restricts the period for which refund interest is paid on a refund arising from a carryback. Subsection 111(5) restricts the use of losses following an acquisition of control, and net capital losses are generally lost on such an acquisition. The refund figures here apply the average rate of tax in each prior year, which understates the recovery where taxable income in that year straddled the small business limit and overstates it where credits rather than rate drove the tax. The prescribed interest rate, the tax rates and the processing time used here are defaults that should be replaced with the corporation’s actual assessed figures and the current published rates. This page is general information, not tax advice.
Three Years Back, Twenty Years Forward
A non-capital loss is the ordinary operating loss of the corporation. It can be applied against taxable income of the three tax years before the loss year, which produces a refund of tax already paid, and against the twenty tax years after it, which reduces tax not yet payable.
The three-year window is the valuable one, because it converts a loss into cash the corporation can use now rather than a deduction it has to wait for. The twenty-year window is generous but not unlimited, and a loss that reaches its expiry unused is simply gone.
The direction of travel matters more than most people assume. A refund of tax paid two years ago arrives within months of the reassessment. A carryforward is worth nothing until the corporation is profitable again, and a corporation that has just had a loss year cannot always promise that.
Which Loss Goes Where
The two loss types behave differently and the distinction decides most of the arithmetic.
| Loss Type | Carry Back | Carry Forward | Can Be Applied Against |
|---|---|---|---|
| Non-capital loss | 3 years | 20 years | Any taxable income |
| Net capital loss | 3 years | Indefinitely | Taxable capital gains only |
| Farm and fishing loss | 3 years | 20 years | Subject to its own restrictions |
| Restricted farm loss | 3 years | 20 years | Farming income only |
A net capital loss carried back to a year with no taxable capital gains does nothing at all. That is the single most common disappointment in a carryback claim: the corporation has a large capital loss, three profitable prior years, and no capital gains in any of them, so the loss sits and waits.
Choosing Which Years to Carry Back To
The corporation chooses how much loss goes to each of the three years. There is no requirement to fill the oldest year first, and the choice is worth making deliberately rather than letting software default it.
The straightforward objective is the largest refund, which means applying the loss first to the year taxed at the highest effective rate. Where income in a prior year sat above the small business limit and was taxed at the general rate, a dollar of loss applied there recovers considerably more than a dollar applied to a year fully inside the small business deduction.
There are reasons to leave income in a prior year. Donations, investment tax credits and foreign tax credits claimed in that year can be displaced by the carryback, and some of them expire. Wiping out a year’s taxable income can waste a credit that would otherwise have been used, which turns part of the refund into an illusion.
Schedule 4, and What Happens After Filing
The loss continuity is reported on Schedule 4, Corporation Loss Continuity and Application, which tracks the opening balance of each loss type, what arose in the year, what was applied, and what is carried forward with its year of origin. The carryback request itself is made with the loss-year return where the position is known at the time of filing.
Where the loss-year return has already gone in, the request is made separately and processed as a reassessment of the prior years. That route is slower, because each affected year has to be reassessed before the refund is issued, and it is worth making the request with the original return wherever the numbers are settled.
None of it happens automatically. A loss sitting on a filed return does not carry itself back, and corporations routinely discover years later that a loss year was filed without a carryback request while the prior years were reassessed for nothing.
Refund Interest Is Not What People Expect
Tax paid two years ago and refunded now does not carry two years of interest. The rules restrict refund interest on a carryback refund to a period tied to the loss year rather than to the date the tax was originally paid, which is why the interest figure on a carryback reassessment is usually far smaller than a straight calculation would suggest.
The same logic runs in the other direction on amounts owing. Where a prior year has unpaid tax, the interest on it is generally computed without regard to a later carryback until a date fixed by reference to the loss year, so carrying a loss back does not retroactively erase the interest that accrued in the meantime.
That asymmetry is deliberate. It removes the incentive to leave tax unpaid in the hope that a future loss will wipe the slate clean, and it means the cash value of a carryback is the tax itself, with interest as a modest addition rather than a meaningful part of the claim.
When Carrying Forward Beats a Refund Now
A loss is worth the rate of tax it saves. Where the corporation expects to be taxed at a higher rate in future than it was in the prior years, the same loss is worth more later, and there is a case for leaving it to carry forward.
That case is weaker than it looks in most situations. It requires the corporation to be profitable enough to use the loss, at a rate high enough to beat the refund, before the twenty years run out, and it gives up cash today for a deduction that depends on a forecast. A corporation that has just recorded a loss is rarely in a position to take that bet lightly.
| Situation | Usually Points To |
|---|---|
| Prior years taxed at the general rate, future at the small business rate | Carry back |
| Prior years inside the small business deduction, strong growth expected | Consider carrying forward |
| Cash flow is tight | Carry back |
| An acquisition of control is in prospect | Carry back before it happens |
| Future profitability genuinely uncertain | Carry back |
The Deadline Nobody Watches
A prior year can be reassessed to give effect to a loss carryback beyond the normal reassessment period, but only within an extended window. Once that window closes on a given year, the loss can still be carried forward, but the tax paid in that year stays paid.
This is where unfiled returns do real damage. A corporation that is three or four years behind may find that by the time the loss year is finally filed, one or more of the prior years it would have reached is out of time. If the filings are not current, the corporate tax cleanup comes first, because the carryback claim depends on it, and the reassessment period checker will show which years are still open.
What This Calculator Does Not Cover
- Acquisition of control, which restricts non-capital losses and generally extinguishes net capital losses
- The marginal rate within a prior year, where taxable income straddled the small business limit
- Credits displaced by the carryback, including donations and investment tax credits that may expire
- Refundable dividend tax on hand and the effect of a carryback on a dividend refund already claimed
- Farm, fishing and restricted farm losses, which follow their own rules
- Allowable business investment losses, which become non-capital losses and convert to net capital losses if unused
- Amalgamations and wind-ups, where losses of a predecessor cannot be carried back by the successor
- Provincial differences outside Ontario in how the carryback is applied
A loss year is worth money, but only if the claim is made on time and allocated properly. Our corporate tax return filing service covers the Schedule 4 continuity, the carryback request and the reassessments that follow it.
Frequently Asked Questions
Loss carrybacks, Schedule 4 and corporate refunds.
Related Calculators and Guides
More tools for corporate tax recovery and catch-up filing.
A Loss Year Is Worth Money If the Claim Is Made Properly
Tell us the loss, the three years before it and what has already been assessed. We will work out the allocation that produces the largest recovery, make the request, and follow the reassessments through to the refund.