The half-year convention is a method of calculating depreciation for tax purposes stipulated by the Internal Revenue Service (IRS) in the United States.
It assumes that property placed in service or disposed of during a tax year was in service or disposed of at the midpoint of the year.
This allows for one-half year’s depreciation to be allowed in the
year the property was placed in service or disposed of, regardless of
when it was actually placed in service or disposed of during that year.