The Complete Guide to Asset Depreciation
When a business purchases a major asset—such as a delivery truck, manufacturing machinery, or computer servers—it cannot immediately deduct the entire cost as an expense on its income statement. Because the asset will provide value to the company over many years, accounting principles (GAAP and IFRS) require the business to spread the cost of the asset out over its "useful life." This process is known as Depreciation.
Useful Life
The Useful Life is the estimated number of years the asset will remain productive and profitable for the business. This is not necessarily how long the item will survive before breaking, but rather how long it will be economically viable to use. Computers typically have a 3 to 5-year useful life, while commercial real estate buildings are depreciated over 39 years.
Salvage Value
Also known as Residual Value or Scrap Value, this is the estimated amount you could sell the asset for at the very end of its useful life. An asset is never depreciated below its salvage value. If you expect a machine to be completely worthless after 10 years, its salvage value is $0.
Method 1: Straight-Line Depreciation
Straight-Line is the simplest and most commonly used method of depreciation. It assumes that the asset loses an equal amount of value every single year until it reaches its salvage value.
Annual Depreciation = (Asset Cost − Salvage Value) ÷ Useful Life
Example: You buy a van for $50,000. You expect to use it for 5 years, after which you can sell it for $10,000 (Salvage Value).
($50,000 - $10,000) ÷ 5 = $8,000 per year in depreciation expenses.
Method 2: Double Declining Balance (Accelerated)
The Double Declining Balance (DDB) method is an "accelerated" depreciation model. It assumes that assets lose the majority of their value in the first few years of ownership (think about how a brand new car loses 20% of its value the second you drive it off the lot).
Instead of deducting a fixed dollar amount, DDB deducts a fixed percentage from the asset's remaining Book Value each year. This percentage is exactly double the Straight-Line percentage rate.
- Higher Tax Write-Offs Early On: Businesses use DDB to claim massive depreciation expenses in the first year, significantly lowering their taxable net income immediately.
- Lower Write-Offs Later: By year 4 or 5, the depreciation expense will be very tiny.
- The Salvage Floor: The formula naturally pushes the book value down, but the math must artificially stop depreciating the exact moment the Book Value hits the Salvage Value.
Tax vs. Book Depreciation
It is very common for businesses to keep two separate sets of books. They may use Straight-Line depreciation for their internal financial reports (to make profits look stable to investors) but use an Accelerated method like MACRS (Modified Accelerated Cost Recovery System in the US) or Block of Assets (in India) for tax filings to maximize immediate tax deductions. Always consult a CPA or Chartered Accountant for tax filings.