Unfortunately, just because the depreciation method was different prior to this date, does not mean it's disqualified. Your property is probably fully depreciated. You would have to look back for the method you started with in 1979, before there was such a thing as accelerated depreciation. 27.5 years is the life under MACRS. Your property has passed through three eras of depreciation; Depreciation, ACRS and MACRS. Each type had its own rules but did not nullify the previous depreciation taken.
Before 1981, you could use any reasonable method for every kind of depreciable property. One of these methods was the straight line method. This method was also used for intangible property. It lets you deduct the same amount of depreciation each year.
To figure your deduction, determine the adjusted basis of your property, its salvage value, and its estimated useful life. Subtract the salvage value, if any, from the adjusted basis. The balance is the total amount of depreciation you can take over the useful life of the property.
Divide the balance by the number of years remaining in the useful life. This gives you the amount of your yearly depreciation deduction. Unless there is a big change in adjusted basis, or useful life, this amount will stay the same throughout the time you depreciate the property. If, in the first year, you use the property for less than a full year, you must prorate your depreciation deduction for the number of months in use.:
The Accelerated Cost Recovery System (ACRS) is a depreciation method that assigns assets periods of cost recovery based on specific IRS criteria. Since 1986, the Modified Accelerated Cost Recovery System (MACRS) has been far more prevalent.
