Declining-Balance Method of Depreciation

The declining-balance method of depreciation is a form of accelerated depreciation that applies a constant percentage rate to an asset's current, declining book value each year, rather than to its original cost. Because book value falls every year as depreciation accumulates, applying the same percentage to a steadily shrinking base produces progressively smaller depreciation expense amounts over time, with the largest depreciation charges occurring in the asset's earliest years and the smallest occurring near the end of its useful life.

Unlike the straight-line method, the declining-balance method does not subtract estimated salvage value before calculating each year's depreciation; instead, the chosen percentage rate is applied directly to the asset's beginning-of-year book value, and the calculation simply stops once book value reaches the estimated salvage value, so the asset is never depreciated below that floor. A common version, the double-declining balance method, uses twice the straight-line rate as its constant percentage, though 150% of the straight-line rate is another commonly used variant.

Equipment costing $50,000, with an estimated $5,000 salvage value and a 5-year useful life, has a straight-line rate of 20% per year. Using double-declining balance at 40%, year one depreciation is 40% of the full $50,000 cost, or $20,000, leaving a $30,000 book value. Year two depreciation is 40% of that $30,000 book value, or $12,000, leaving $18,000, and the pattern continues, with each year's charge smaller than the last, until book value approaches the $5,000 salvage floor.

Companies often favor accelerated depreciation methods like declining balance for income tax purposes because they front-load the tax deduction into an asset's earlier years, deferring tax payments to later years and improving near-term cash flow, even though total depreciation over the asset's full life is identical under any method. Some businesses also use an accelerated method for financial reporting when they believe an asset genuinely loses economic value and usefulness faster in its early years, such as technology equipment that becomes less competitive quickly even while still functional.

Straight-line depreciation produces the same expense every year, while declining balance produces a steadily shrinking expense, meaning a company's choice between the two methods can significantly affect reported profit in any given early year, even though the two methods converge to the identical total depreciation expense by the time the asset is fully depreciated. This is purely a timing difference, not a difference in the ultimate amount depreciated, which is why analysts comparing two otherwise similar companies using different depreciation methods adjust for the difference rather than treating one company's early profitability as genuinely superior to the other's.

Because declining balance never fully depreciates an asset down to its salvage value on its own in a clean, even way, some companies switch from declining balance to straight-line partway through an asset’s life once straight-line would produce a larger remaining annual deduction over the years left, a technique sometimes used to maximize allowable depreciation under certain tax rules while still capturing the early-year acceleration benefit that declining balance provides.