You can make your own: To make buttermilk, use 1 cup milk and 1 tablespoon lemon juice or white vinegar. Allow it to sit for a few minutes. If you do purchase buttermilk and have extra, freeze it in 1 cup containers or in Ziplock bags. You can also purchase powdered buttermilk in grocery stores.
Straight-line depreciation allows an equal portion of the laptop's cost to be claimed in each year over the total depreciation period. If the cost of the computer was $1,000, for example, then $200 a year can be included in the company's total depreciation amount each year for five years.
The time period for deducting depreciation depends on the type of investment. If the property is a commercial property, then the depreciation period is 39 years (as opposed to 27.5 years for residential property). Using a straight line depreciation method for a commercial property costing $2 million dollars, for example, you would receive an annual deduction of $51,282 ($2M / 39 = $51,282).