what does useful life mean 
useful life is the accounting estimate of the number of years an asset is likely to remain in service for the purpose of producing income the irs determines the useful life for various assets laying out the length of time in which they can be depreciated for example the useful life according to the irs for automobiles is five years while residential rental properties have a useful life of 27 5 years 11the bottom linethe modified accelerated cost recovery system macrs is a depreciation method used for tax purposes and is more beneficial than other methods of depreciation the irs outlines two types of macrs gds and ads ads is usually only used in unique circumstances 