Documentation - useful life of an asset

Possibly, but you would have to be specific about what it is. For example, it the asset was an item of plant or equipment that according to its technical specification has an operating capacity expressed as 10,000 hours - then if the machine is operated 8 hours a day, 5 days a week for 52 weeks a year, i.e. 2,080 hours, the useful life would be 5 years. (Remember - it should never be thought of as "exact" because useful life is an accounting estimate.) Indeed it does vary from entity to entity and asset to asset. So IT equipment might be 2-3 year, cars might be 5 years, etc, etc. Management should have a basis for estimates not only of uselife but method - straight-line or reducing balance - and in the case of straight-line, residual value (if any). The auditor then audits management's justification - so if, for example, management asserts that cars are replaced after every 5 years, seeing that written in an accounting manual or concluded on in a board minute would not be sufficient evidence. The auditor would example the disposals of cars - how old are they when disposed of? Also, selecting from the asset register, inspect cars that have been fully-depreciated (i.e. > 5 years old). Are they still being used in the business? etc, etc