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The half-year rule, explained

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By EverStone CPA · Published September 2026 · 6 min read

Quick answer: The half-year rule is the CCA convention that, in the year you buy a depreciable asset, you may generally claim capital cost allowance on only half of the net additions to the class — as if the asset had been owned for six months regardless of the purchase date. A Class 8 asset at 20% therefore yields a 10% first-year claim. Accelerated investment incentives have at times suspended the rule for eligible property; the CRA’s CCA pages state which years and classes.

What the rule does

Capital cost allowance is the tax version of depreciation: rather than deducting the cost of a truck, a computer or a piece of equipment in the year you buy it, you deduct a percentage of the pooled balance of its class each year. The half-year rule is a first-year adjustment to that pool. In the year of acquisition, the amount on which you calculate CCA is reduced by half of the net additions to the class — purchases less dispositions — so the first year’s claim is roughly half of what the class rate would otherwise give.

The effect is easiest to see on one asset. Buy a $10,000 Class 8 asset (20% declining balance) in a year with no other additions or disposals: the half-year rule reduces the amount subject to CCA to $5,000, so the first-year claim is $1,000 rather than $2,000. The unclaimed $1,000 is not lost; it stays in the undepreciated capital cost of the class and is claimed over the following years at the full rate.

Why it exists

Without it, an asset bought on 30 December would earn a full year of CCA for one day of ownership. The rule assumes, on average, that assets are bought halfway through the year, and it applies that assumption to everyone rather than tracking purchase dates asset by asset. It is a simplification that favours the CRA slightly in year one and the taxpayer slightly thereafter.

When it does not apply

  • Accelerated investment incentive property. For eligible property acquired within the incentive’s window, the half-year rule is suspended and the first-year claim is enhanced rather than halved. The incentive has a phase-out schedule; whether a given purchase qualifies depends on the acquisition date and the class. The CRA’s CCA pages carry the current table — do not assume the enhanced treatment still applies to this year’s purchase without checking.
  • Immediate expensing. Where a corporation elected immediate expensing on qualifying property in the years that measure was available, the property was written off in full and no half-year adjustment arose.
  • Certain classes and situations. A handful of classes are excluded from the rule by regulation, and property acquired in a non-arm’s-length transaction that was already depreciable to the seller is treated differently. These are exceptions your accountant checks class by class.

What it means for a purchase decision

The rule rarely changes whether to buy an asset, but it does change when the tax deduction lands. A purchase made in the last month of the fiscal year still earns the half-year claim for that year, which is why year-end equipment purchases are a legitimate timing decision rather than a trick — provided the asset is available for use before the year end, which is its own test. A purchase made the first week of the following year earns nothing for the year just closed.

The same $10,000 Class 8 asset, first-year claim under each treatment
TreatmentBase for year oneFirst-year CCA at 20%
Half-year rule applies$5,000$1,000
No half-year rule (illustrative only)$10,000$2,000
Accelerated investment incentive, where eligibleenhanced — per the CRA table for the acquisition yearmore than $2,000

The figures are the rule applied to a round number, not a projection for any business; which line applies to a real purchase depends on the class, the date and the current incentive schedule.

Related

CCA classes explained · Equipment CCA classes · Immediate expensing · Glossary

Sources: CRA — Basic information about capital cost allowance · CRA — T4012 T2 Corporation Income Tax Guide. General information, not advice.

Common questions

Frequently asked

Does the half-year rule apply to a used asset?+
Yes, in general. The rule looks at net additions to the class in the year, not at whether the asset is new. The exception is property acquired from a non-arm’s-length person who already held it as depreciable property, which follows its own rules.
If I buy in December, do I still get the half-year claim?+
Yes, provided the asset is available for use by the year end. The rule assumes a mid-year purchase for everyone, so a December purchase and a January purchase of the previous year get the same first-year treatment.
Is the half of the cost I could not claim lost?+
No. It remains in the undepreciated capital cost of the class and is claimed in later years at the full rate for the class.

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