Half-Year Rule

Definition

The half-year rule is the mechanism in Regulation 1100(2) that reduces the CCA base for net additions to a class by 50% in the year those additions first become available for use. The intent is to approximate the fact that purchases are made throughout the year: on average, a new asset is available for roughly half the tax year, so the first-year deduction is halved.

Key rules

• The adjustment applies to net additions, meaning additions to the class in the year less the amount by which dispositions from the class during the year reduce UCC. The half-year reduction is capped at net additions and cannot turn positive into negative.
• The half-year rule is suspended for Accelerated Investment Incentive Property (AIIP), replaced by a front-loaded first-year deduction. See AIIP.
• Regulation 1100(2.2) specifies exclusions: property acquired from a non-arm's-length person is generally denied the regular half-year treatment to the extent it was already in a depreciable class at the transferor.
• "Available for use" is defined in ITA s.13(26) to (32). An asset purchased but not installed or operational by year end does not yet attract CCA and therefore no half-year reduction either; the starting UCC simply carries forward until the asset is available.
• Class 10.1 passenger vehicles have their own half-year treatment embedded in Regulation 7307 via the capital cost limit. Class 12 properties (software under 100% CCA) are mostly exempt from the half-year rule but some sub-items still apply; confirm the specific paragraph of Class 12.

Example

A BC corporation with a calendar year end has class 8 UCC of $6,000 on January 1, 2026. During 2026 it buys $12,000 of new desks and sells old desks for $2,000 (original cost $3,500). No AIIP.

1. Additions = $12,000. Dispositions reduce UCC by the lesser of proceeds and original cost: $2,000.
2. Net additions = $12,000 − $2,000 = $10,000.
3. Half-year adjustment = 50% × $10,000 = $5,000.
4. CCA base = $6,000 + $12,000 − $2,000 − $5,000 = $11,000.
5. CCA for 2026 = $11,000 × 20% = $2,200.
6. Closing UCC = $6,000 + $12,000 − $2,000 − $2,200 = $13,800.

In year 2 and beyond, the half-year adjustment is no longer applied to the same asset, so the full UCC attracts the class rate.

Common mistakes

• Reducing additions by 50% on the books instead of reducing only the CCA base. The closing UCC must still reflect the full cost minus actual CCA taken.
• Applying the half-year rule to AIIP, resulting in an artificially low first-year deduction.
• Forgetting that dispositions first reduce the half-year adjustment base. Net additions can be zero or negative.
• Taking CCA on an asset that was ordered but not yet available for use. The correct treatment is to defer recognition until the "available-for-use" date.
• Missing the asymmetric rule in Reg 1100(2.2) for non-arm's-length transfers.

Related concepts

The half-year rule is the default; it is replaced by AIIP or immediate expensing for qualifying property. It is a component of every CCA calculation, interacting with class specifics like Class 8, Class 10, and Class 50.