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Declining Balance Depreciation Explained: How It Differs From Straight-Line
Two accountants can depreciate the exact same $20,000 machine and report completely different expenses in year one — both correctly, just using different methods.
Straight-line depreciation spreads an asset's cost evenly across its useful life, which is intuitive but not always realistic — a delivery van or a laptop typically loses more of its value in year one than in year five. Declining balance depreciation, sometimes called reducing balance depreciation, is built to match that pattern instead.
The core idea
Rather than depreciating a fixed dollar amount every year, declining balance depreciation applies a fixed percentage to the asset's remaining book value each year. Because the book value shrinks every year, the depreciation expense shrinks along with it — largest in year one, smallest in the asset's final years.
The formula
Depreciation Expense (Year N) = Book Value at Start of Year N × Depreciation Rate
The double-declining balance variant
The most common version, double-declining balance, uses twice the straight-line rate. For an asset with a 5-year useful life, the straight-line rate is 1 ÷ 5 = 20% per year, so the double-declining rate is 40%.
A worked example
A $20,000 machine with a 5-year useful life and an estimated $2,000 salvage value, depreciated using double-declining balance at 40%:
| Year | Book value (start) | Depreciation (40%) | Book value (end) |
|---|---|---|---|
| 1 | $20,000.00 | $8,000.00 | $12,000.00 |
| 2 | $12,000.00 | $4,800.00 | $7,200.00 |
| 3 | $7,200.00 | $2,880.00 | $4,320.00 |
| 4 | $4,320.00 | $1,728.00 | $2,592.00 |
| 5 | $2,592.00 | $592.00 (capped at salvage value) | $2,000.00 |
The salvage value cap
Unlike straight-line depreciation, the declining balance formula doesn't automatically stop at the salvage value — it has to be capped manually. In the example above, year 5's calculated depreciation (40% of $2,592 = $1,036.80) would have pushed book value below the $2,000 salvage floor, so the expense is capped at $592 instead, exactly enough to bring book value to $2,000 and no further.
Comparing total depreciation over the asset's life
| Method | Year 1 expense | Year 5 expense | Total depreciated by year 5 |
|---|---|---|---|
| Straight-line | $3,600 | $3,600 | $18,000 |
| Double-declining balance | $8,000 | $592 | $18,000 |
Why the total is the same but the timing isn't
Both methods depreciate the same total amount over the asset's useful life — the difference is entirely in timing. Declining balance front-loads the expense, which reduces reported profit (and, in some tax systems, taxable income) more in the earlier years, an approach some businesses prefer for assets that genuinely lose value quickly, or for the tax timing benefit of deferring some tax liability to later years.
When each method is typically used
- Straight-line: simpler to calculate and explain, commonly used for assets that lose value fairly evenly, such as buildings and furniture.
- Declining balance: better matches assets that lose value quickly early on, such as vehicles, computers and manufacturing equipment, and is used in some tax systems specifically because of the accelerated deduction it allows.
Switching to straight-line partway through, a common real-world practice
Some accounting systems switch from declining balance to straight-line depreciation partway through an asset's life, once straight-line on the remaining book value and remaining years would produce a larger expense than continuing with declining balance — ensuring the asset still reaches its salvage value by the end of its useful life without an awkward, tiny final-year adjustment.
A note for commerce and accounting students
Exam questions on declining balance depreciation almost always specify the rate to use directly, removing the need to calculate double the straight-line rate yourself — but real-world use, including for tax filings, typically requires determining or confirming that rate from the applicable accounting standard or tax code first.
A full five-year schedule with the salvage cap applied
Take an asset costing $10,000 with a $1,000 salvage value and a five-year life, using double-declining balance at 40% (twice the straight-line rate of 20%). Year 1 depreciation is $4,000, leaving a book value of $6,000. Year 2 is $2,400 (book value $3,600), year 3 is $1,440 (book value $2,160) and year 4 is $864 (book value $1,296). In year 5, 40% would be $518, but that would take the book value below salvage, so depreciation is capped at $296, leaving exactly $1,000.
Total depreciation is $4,000 + $2,400 + $1,440 + $864 + $296 = $9,000, which equals cost minus salvage, the same total straight-line produces at $1,800 a year. The difference is timing: this method deducts far more in year 1 than in year 5. Which method is permitted for tax purposes depends on your local rules, so use this as an accounting illustration and confirm with a qualified adviser for filings.
Check the book value against the salvage limit
A declining-balance schedule should never depreciate an asset below its stated salvage value when that value is part of the method. After each period, compare the calculated depreciation with the remaining depreciable amount and cap the final charge when necessary. This simple check catches many spreadsheet errors, especially when a high depreciation rate is applied over several years.
Frequently asked questions
Is declining balance depreciation allowed for tax purposes?
It depends on the tax jurisdiction — some countries permit or require accelerated depreciation methods for tax reporting even when straight-line is used for financial statements, so check local tax rules or consult an accountant.
Can the depreciation rate be something other than double the straight-line rate?
Yes — 150% declining balance and other rates are also used in practice; 'double' declining balance specifically refers to using twice the straight-line rate.
What happens if an asset is sold before it's fully depreciated?
The difference between the sale price and the remaining book value is recorded as a gain or loss on disposal, regardless of which depreciation method was used to reach that book value.
Does declining-balance depreciation always reach zero?
Not necessarily. If a salvage value is specified, depreciation stops at that value. The final period may therefore need an adjustment.
Why does declining balance produce larger early deductions?
The method applies a rate to the remaining book value, so the depreciation amount is largest when the asset's book value is largest.
Conclusion
Declining balance depreciation reaches the same total depreciation as straight-line over an asset's life, but front-loads the expense to match assets that lose value quickly. The formula is simple — remaining book value times a fixed rate — but remember to cap the final year's expense at the salvage value rather than letting the formula run past it.
Figures in this article are illustrative. Results depend on your own rates, fees, taxes and circumstances, and are for educational and planning purposes rather than financial advice.