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Decommissioning liabilities are costs you’re committed to paying later, when a well, mine, plant or site is closed and cleaned up. In your books they’re a promise to pay that has to be written down before the money leaves. What exactly you record, and when, is set by the accounting standards your business follows, and this is a topic where you need your accountant in the room.
What counts as a decommissioning liability?
It’s an obligation, often legal, tied to closing or removing an asset. Think of a company that has to take down equipment, restore land or seal a site once operations end. The cost is in the future, but the duty exists today.
Standard setters use the term asset retirement obligation. Canada’s public sector standard board, for instance, has a project on legal obligations linked to the retirement of tangible capital assets. We could only read the project page, not the finished standard, so we can’t tell you the measurement rules. The private sector rules sit in the CPA Canada Handbook, which we couldn’t open either. That’s a gap we’d rather admit than fill with a guess.
What should your books hold for one?
Whatever the standard says, a clean file has the same parts. If an auditor, lender or the CRA asks about the balance, you should be able to answer in minutes.
| Item | What to keep |
|---|---|
| Source of the duty | The permit, lease, contract or law that creates it |
| Estimate | The written cost estimate, who prepared it and when |
| Assumptions | Timing, inflation, discount rate and how each was chosen |
| Related asset | Which asset the obligation belongs to |
| Changes | Each revision, the reason and the journal entry |
| Spending | Invoices for any work done against the balance |
Give the liability its own account. Don’t bury it in general accruals, where it will be forgotten until year end.
How do decommissioning liabilities reach the tax return?
That’s the part people get wrong, so read this slowly. Accounting and tax are separate systems. The CRA says you can’t deduct the full cost of depreciable property in the year you buy it, and instead claim capital cost allowance spread over several years. That’s the tax rule for the asset itself.
What we couldn’t confirm is how the CRA treats an estimated future clean-up cost you’ve recorded in the books. The page we read on capital cost allowance says nothing about removal or restoration costs. Until you have an answer from your accountant, don’t assume the estimate lowers your taxable income.
The corporate tax calculator shows why it matters. On $300,000 of active business income in Ontario, tax is $35,088 for a calendar 2026 year. On $250,000 it’s $29,240. That $5,848 gap is what a $50,000 difference in taxable income would do, and whether your estimate produces that kind of change is exactly the question to ask.
A worked way to think about the numbers
Say your accountant estimates $50,000 to restore a site in a few years. If the books record it as a liability now, your profit on paper falls. Your tax bill may not move at all until the work is done. Two sets of numbers, and both need to be explained.
Now look at what it does to margins. The profit margin calculator lets you test how a big cost changes the share you keep from each sale. And if the closing cost is part of a bigger investment decision, the ROI calculator shows if the project still pays after clean-up.
For other business tax tools, the business tax hub lists them all.
Mistakes and limits
The first is ignoring the obligation because the money isn’t due for years. The duty still sits in your books, and a lender may ask about it.
The second is a stale estimate. Costs, timing and rules move, so review the number at least once a year and log the change.
Third, mixing up the books and the tax return. A number that’s right for one isn’t automatically right for the other.
Fourth, weak records. The CRA expects you to keep records for six years from the end of the last tax year they relate to, and you remain responsible when someone else keeps them. For a liability that may last decades, keep the supporting file well beyond that, since the estimate has to be defended when the work is finally done.
This page can’t tell you which standard applies to you. That depends on what kind of body you are (a private company, a public entity or a government) and on what your lenders and shareholders expect, and there’s no way to guess it from here. Ask your accountant, and ask for the answer in writing.
Where the numbers come from
The record-keeping rules come from the Canada Revenue Agency’s guide to keeping records and its page on capital cost allowance. The description of the public sector project comes from the Financial Reporting and Assurance Standards Canada website. Tax figures are from the calculators on this site, using 2026 data. We couldn’t confirm the measurement rules or the tax treatment of the estimate, so we’ve said so.
Frequently asked questions
What is a decommissioning liability?
A cost you're committed to paying later to close, remove or restore an asset or site. The duty exists now even though the money is spent later.
Which accounting standard applies to it?
That depends on the type of organization. We couldn't read the standards themselves, so ask your accountant which one you follow.
Can I deduct the estimated cost on my tax return?
We couldn't confirm this from an official page. The CRA says depreciable property is claimed through capital cost allowance over several years, so ask your accountant before you assume.
What records should I keep?
The source of the obligation, the written estimate, your assumptions, each revision and invoices for work done. The CRA asks for business records for six years.
How often should the estimate be reviewed?
At least once a year, and whenever costs, timing or legal requirements change. Record each change with the reason.
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Information only. This page is general information, not tax, legal or accounting advice. Tax-Services.ca is an independent publisher: we don't prepare or file tax returns or offer tax services, and we have no connection with the CRA, Revenu Québec, any government or any company named on this page. Check the figures that matter with an official source or a qualified professional.