For those that are not as familar with depreciation. You have to pay taxes on profits, when you buy equipment/machines/buildings/etc. (called PP&E) that last for many years the tax code forces you to recognize the expense for tax purposes over the useful life of the asset. So you pay $100 for a new piece of equipment that will last ten years, every year for ten years you get to recognize $10 of expenses, so your taxable income is lowered by $10 each year. The tax law let everyone expense the entire value in the first year, so it encouraged purchases of PP&E as $1 dollar saved today is worth more then $1 saved ten years from now.