If you are literally just arbitrarily assigning a useful life of one year to all of your depreciable equipment and expensing them you are intentionally lowering your income taxes and you had better hope you never get audited. The IRS has a table (I believe rightinNYC posted) you can use for the useful life of your equipment/assets and you can depreciate them using a number of methods (modified accelerated cost recovery/straightline). The tax cut changes this. This is for taxes. Your own personal books can look different, but this is how you report it to the IRS.