If useful life is:The applicable percentage is:
Less than 4 years.........................................0%
4 years or more but less than 6 years ...............33 1/3%
6 years or more but less than 8 years ...............66 2/3%
8 years or more ........................................100%
The useful life of any property, for purposes of this section, is determined as of the date the property is first placed in service or use in this state by the taxpayer, determined in accordance with such rules and requirements the tax commissioner may prescribe.
W. Va. Code § 11-13Q-8