Half-Year Convention for Depreciation

A depreciation rule that assumes the depreciation on a fixed asset is halved for the first and additional last year

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What is the Half-Year Convention for Depreciation?

The half-year convention for depreciation assumes fixed assets have been in service for one-half of its first year despite when it was actually acquired. This rule is applied by tax authorities to restrict the maximum allowable claim for depreciation to one half of the annual amount.

Half-Year Convention for Depreciation

The other half of the depreciation is applied to the final year the asset is depreciated, also under the assumption that the asset will no longer be used or disposed of halfway through that final year. The half-year convention applies to all forms of depreciation methods, such as straight-line depreciation, sum-of-the-years digits, modified accelerated cost recovery systems, and double-declining balance.


  • The half-year depreciation convention is a tax rule that assumes the asset is obtained and disposed of partly through the acquisition and disposal year. The maximum allowable depreciation amount is therefore half the annual amount.
  • It is crucial to remember that deprecation is halved in the first year, with the remainder of that depreciation being taken in the last year of the asset’s useful life.
  • Rules created by the U.S. Internal Revenue Service (IRS) aim to prevent manipulation of tax deductions by restricting the maximum allowed.

Half-Year Convention for Depreciation Example

The allocation of depreciation for the half-year convention can be difficult to grasp. To get a better understanding, an example of a half-year convention with a depreciation schedule is shown below.

Example: Company A purchases a manufacturing machine for $25,000 on March 1, 2020. The manufacturing machine’s useful life is five years. With the application of a half-year convention, the depreciation schedule is as follows:

  • Straight-line Depreciation = Cost of Asset / Useful Life = ($25,000 / 5) = $5,000 per year.
  • Application of Half-year Convention = ($5,000 / 2) = $2,500 for first and additional year.
  • Depreciation Schedule:

Half-Year Convention - Depreciation Schedule

As the table shows, the first year of depreciation is halved due to the half-year convention. To make up for it, an extra year is added to the end of the depreciation schedule.

What is a Depreciation Convention?

A depreciation convention is a rule that is used to determine four different criteria:

  • The depreciation method you can use
  • The depreciation schedule you can use, dependent on the useful life
  • The amount of depreciation that can be claimed once the fixed asset is disposed of
  • The amount of depreciation that can be claimed in the first and last year of the fixed asset’s recovery period

As a whole, depreciation conventions govern when and how depreciation is calculated.

Types of Depreciation Conventions

As for the types of depreciation conventions, nine conventions govern when and how depreciation is calculated. The conventions are listed and discussed below:

  • FM = Full Month: The fixed asset receives a full month of depreciation during the month when it is placed in service. It does not receive depreciation for the month of disposal.
  • HM = Modified Half Month: If the fixed asset is put into service during the first half of the month, it receives a full month of depreciation. If it is put into service during the second half of the month, the calculation of depreciation begins the preceding month.
  • MM = Mid-Month: The fixed asset receives half a month of depreciation for the month it was placed into service and half a month of depreciation when disposed of.
  • NM = Next Month: Depreciation for the fixed asset begins one month after it is placed into service and receives one month of depreciation when disposed of.
  • HY = Half-Year: Depreciation is halved for the first and last year once it is in service.
  • MY = Modified Half-Year: If put into service before the midpoint of the year, the fixed asset receives a full year of depreciation for the first year, but none on the last. If put into service after the midpoint of the year, depreciation is calculated the following year. Also, a full year of depreciation is received once disposed of.
  • FY = Full Year: The fixed asset received a full year of depreciation when put into service and when it is disposed of.
  • AD = Actual Days: The fixed asset receives depreciation every day it is in service during a company’s fiscal year.
  • MQ = Mid-Quarter: The fixed asset receives half of one quarter’s depreciation for the quarter that it was placed into service. Same situation for disposal.

Tax Implications

How and when depreciation is calculated directly affects an organization’s tax status. A half-year convention does not require taxpayers to prove when the fixed asset was placed into service. Instead, the U.S. Internal Revenue Service (IRS) created a rule that assumes fixed assets are placed into service on July 1st of the year it was actually placed in service.

The IRS created the rule because taxpayers would be enticed to purchase fixed assets in the second half of the year and aggressively claim full depreciation deductions. As for taxpayers, the rule clearly outlines how much depreciation can be deducted in the first year as the asset is assumed to be put into service on July 1st.

Related Readings

CFI is the official provider of the global Commercial Banking & Credit Analyst (CBCA)™ certification program, designed to help anyone become a world-class financial analyst. To keep advancing your career, the additional CFI resources below will be useful:

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