What depreciation is actually for
Depreciation spreads the cost of a long-lived asset - equipment, a vehicle, office furniture - across the years it’s actually used, rather than expensing the full cost the moment it’s bought. It’s an accounting and tax allocation, not a valuation: depreciation schedules don’t try to track what the asset would actually sell for today.
Straight-line: the same amount, every year
Straight-line depreciation divides an asset’s depreciable cost evenly across its useful life - the same fixed amount is expensed every year until the asset is fully depreciated. It’s the simplest method to calculate and forecast, and it’s the natural fit for assets that genuinely provide roughly equal value every year, like office furniture or a building.
Declining balance: front-loaded, tapering off
Declining balance applies a fixed percentage rate to the asset’s remaining (not original) book value each year - so the deduction is largest in the first year and shrinks as the book value shrinks. It’s an accelerated method, often used for assets that lose usefulness or value quickly, like technology or vehicles, and it’s sometimes called "double declining balance" when the rate used is double the straight-line rate.
| Year | Straight-line expense | Declining balance expense (double-declining) |
|---|---|---|
| 1 | $2,000 | $4,000 |
| 2 | $2,000 | $2,400 |
| 3 | $2,000 | $1,440 |
| 4 | $2,000 | $864 (or switch to straight-line for the remainder) |
| 5 | $2,000 | Remaining balance to fully depreciate |
Straight-line vs. declining balance on a $10,000 asset, 5-year life (illustrative)
The total is the same either way
Over the full useful life of the asset, both methods depreciate the exact same total amount - the depreciable base. The only real difference is timing: declining balance gives a larger deduction earlier, straight-line spreads it evenly. Neither method changes how much total depreciation you’re ultimately entitled to.
Choosing between them
Which fits which asset
Straight-line fits
- Assets that provide roughly equal benefit every year
- Buildings, office furniture, long-life fixtures
- Businesses that want predictable, simple expense forecasting
Declining balance fits
- Assets that lose usefulness or value quickly
- Technology, vehicles, equipment prone to obsolescence
- Businesses wanting larger tax deductions in the earlier years of ownership
Why the choice affects more than just your tax bill
Depreciation method also shapes your financial statements: a declining-balance asset shows lower book value earlier, which affects your balance sheet and any ratios calculated from it. Two businesses that bought identical equipment can show meaningfully different reported profit in year one purely from this choice - worth knowing when comparing your numbers to a competitor’s, or to your own prior years if you ever switch methods.
Worked example: why timing matters to cash flow
A business expecting a strong profit year might prefer declining balance - the larger early deduction reduces taxable income right when it would otherwise be highest. A business wanting flat, predictable expenses for internal budgeting might prefer straight-line, even if it means a smaller deduction in year one.
Does depreciation method choice change how much I can ultimately deduct?
No - the total depreciation over an asset’s full useful life is identical under both methods, since it always equals the same depreciable base. Only the timing of when you recognize that expense differs.
Which method should I use for a computer or vehicle?
Declining balance is often a better fit for assets that lose usefulness or value quickly, like technology and vehicles, since it front-loads the deduction while the asset is still delivering most of its value. Straight-line suits assets that provide steady value over a longer, more even life.
Can I switch depreciation methods after I’ve started using one?
Generally not casually - switching methods has real tax and disclosure implications in most jurisdictions, and typically requires justification and consistent application going forward. Talk to your accountant before changing methods on an asset already in use.
Depreciation doesn’t ask what the asset is worth today. It asks how much of its cost you’ve earned the right to deduct so far.
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