8.2 Depreciation methods

Depreciation methods overview

Depreciation is the systematic allocation of a long-lived asset's cost over its useful life. The core idea is the matching principle: you're spreading the expense of the asset across the same periods in which it helps generate revenue. The method you choose affects reported income, asset values on the balance sheet, and key financial ratios, so getting this right matters for both financial reporting and decision-making.

Several methods exist, each producing a different pattern of expense recognition. The right choice depends on the asset's nature, its expected usage pattern, and the company's reporting objectives.

Straight-line depreciation

Calculation of straight-line depreciation

The straight-line method spreads an equal amount of depreciation expense across each year of the asset's useful life. It's the most commonly used method and the simplest to apply.

$\text{Annual Depreciation Expense} = \frac{\text{Cost} - \text{Salvage Value}}{\text{Useful Life}}$

Example: An asset costs $100,000, has a salvage value of $10,000, and a useful life of 5 years.

$\frac{\$100{,}000 - \$10{,}000}{5} = \$18{,}000 \text{ per year}$

Each year, you'd record $18,000 in depreciation expense, and after 5 years the asset sits on the books at its $10,000 salvage value.

Advantages of straight-line method

• Simple to calculate and easy to explain to stakeholders
• Produces a consistent expense each year, which helps with budgeting and forecasting
• Works well for assets with a relatively even usage pattern over their life, like office furniture or buildings

Disadvantages of straight-line method

• Doesn't reflect the reality that some assets (vehicles, technology) lose value much faster in their early years
• May not accurately match the economic benefit the asset provides in each period
• Can produce a significant gain or loss on disposal if the asset's actual useful life or salvage value turns out to differ from original estimates

Accelerated depreciation methods

Accelerated methods front-load depreciation expense into the earlier years of an asset's life. This better reflects assets that deliver more economic benefit (or lose value faster) early on. The trade-off: higher expense early means lower reported income in those years, with the pattern reversing later.

Double-declining balance method

This method applies a constant rate, typically double the straight-line rate, to the asset's declining book value each year. Notice that salvage value is not subtracted when computing each year's expense; instead, you stop depreciating once book value reaches salvage value.

$\text{Annual Depreciation Expense} = \text{Book Value at Beginning of Year} \times \frac{2}{\text{Useful Life}}$

Example: Using the same $100,000 asset with a 5-year life:

• The straight-line rate is $\frac{1}{5} = 20\%$, so the double-declining rate is 40%.
• Year 1: $\$100{,}000 \times 0.40 = \$40{,}000$
• Year 2: $\$60{,}000 \times 0.40 = \$24{,}000$
• Year 3: $\$36{,}000 \times 0.40 = \$14{,}400$

The expense drops each year as the book value shrinks. In practice, companies often switch to straight-line in the later years to fully depreciate the asset down to salvage value.

Sum-of-the-years' digits method

This method also front-loads depreciation, but it applies a changing fraction to the depreciable base (cost minus salvage value) each year.

$\text{Annual Depreciation Expense} = \frac{\text{Remaining Life}}{\text{Sum of Years' Digits}} \times (\text{Cost} - \text{Salvage Value})$

The sum of years' digits for an asset with useful life $n$ is:

$\text{Sum of Years' Digits} = \frac{n(n+1)}{2}$

Example: For a 5-year asset, the sum is $\frac{5(6)}{2} = 15$. In Year 1, the fraction is $\frac{5}{15}$; in Year 2, $\frac{4}{15}$; and so on. Each year's fraction gets smaller, producing a steadily declining expense.

Units-of-production method

Rather than tying depreciation to the passage of time, this method ties it to actual usage or output.

$\text{Depreciation Expense} = \frac{\text{Units Produced in Period}}{\text{Total Estimated Units Over Life}} \times (\text{Cost} - \text{Salvage Value})$

This is ideal for assets whose wear and tear depends on how much they're used, not how long you've owned them. A printing press that runs double shifts one year and sits idle the next would show very different expense in each year, which better matches the economic reality. Manufacturing equipment and delivery vehicles are common candidates.

Comparison of depreciation methods

Impact on financial statements

• Different methods create different expense patterns, which directly affect both the income statement (net income) and the balance sheet (net book value of assets).
• Accelerated methods produce lower net income in early years and higher net income in later years compared to straight-line. Over the asset's full life, total depreciation expense is the same under every method; only the timing differs.
• The method you choose can significantly shift financial ratios like return on assets and debt-to-equity, which matters when analysts or lenders are evaluating the company.

Tax implications

• Tax regulations may require specific depreciation methods for certain asset types (see MACRS below).
• Accelerated methods provide a tax deferral benefit: higher early deductions reduce taxable income now, pushing tax payments into later years. You don't pay less tax overall, but you benefit from the time value of money.
• When the depreciation method used for tax differs from the one used for financial reporting, the difference creates temporary differences that give rise to deferred tax assets or liabilities on the balance sheet.

Industry-specific considerations

• Some industries gravitate toward particular methods because of the nature of their assets. The oil and gas industry, for instance, commonly uses units-of-production for extraction equipment since output directly drives asset consumption.
• Companies should consider industry norms when selecting methods to maintain comparability with peers in financial analysis.

Changes in depreciation methods

Accounting for changes in estimates

Changes in the estimated useful life or salvage value of an asset are treated as changes in accounting estimates under ASC 250. These are accounted for prospectively: you apply the new estimate to the current and future periods only, with no restatement of prior periods.

The remaining depreciable base (current book value minus revised salvage value) is spread over the revised remaining useful life. The nature and effect of the change must be disclosed in the notes to the financial statements.

Retrospective vs. prospective application

• Prospective application applies the new estimate or method to the current and future periods only. This is used for changes in estimates.
• Retrospective application involves restating prior period financial statements as if the new method had always been in effect. This is used for changes in accounting principles.
• A change in depreciation method (e.g., switching from straight-line to double-declining balance) is treated as a change in accounting estimate effected by a change in accounting principle under U.S. GAAP. Despite the name, it is accounted for prospectively, not retrospectively. This is a common exam trap.

Disclosures for changes in methods

• The company must disclose the nature of and reason for the change.
• Financial statements should report the effect of the change on income from continuing operations, net income, and related per-share amounts for the current period.
• If the change occurs in an interim period, the company should disclose the effect on prior interim periods of the current fiscal year.

Impairment of long-lived assets

Identifying impairment indicators

Impairment occurs when the carrying amount (book value) of a long-lived asset exceeds its recoverable amount. You don't test for impairment every period; instead, you watch for triggering events or indicators:

• Significant decline in market value
• Major change in how the asset is used or its physical condition
• Adverse changes in the legal or business climate
• Operating or cash flow losses associated with the asset

If any of these indicators are present, the company must perform a recoverability test.

Measuring impairment losses

Under U.S. GAAP (ASC 360), impairment testing for long-lived assets follows a two-step process:

1. Recoverability test: Compare the asset's carrying amount to the sum of its undiscounted expected future cash flows. If the carrying amount exceeds the undiscounted cash flows, the asset is impaired.
2. Measurement: The impairment loss equals the difference between the asset's carrying amount and its fair value. Fair value can be determined using market prices, present value of future cash flows (discounted this time), or appraisals.

The impairment loss is recognized on the income statement, and the asset's carrying amount is written down to its new fair value, which becomes the new cost basis for future depreciation.

Reversal of impairment losses

• Under U.S. GAAP, once an impairment loss is recognized on a long-lived asset held for use, it cannot be reversed, even if the asset's value later recovers. The write-down is permanent.
• Under IFRS (IAS 36), reversal of impairment losses is permitted (up to the original carrying amount, adjusted for depreciation that would have been taken). This is a key GAAP vs. IFRS difference to know.
• The U.S. GAAP prohibition reflects the conservatism principle and aims to prevent potential earnings management through selective reversals.

Depletion of natural resources

Calculation of depletion expense

Depletion is the allocation of the cost of natural resources (oil, gas, minerals, timber) over their estimated recoverable reserves. It works just like the units-of-production method, but applied to extractive assets.

$\text{Depletion Expense} = \frac{\text{Units Extracted in Period}}{\text{Total Estimated Recoverable Reserves}} \times \text{Depletable Cost}$

The depletable cost includes the purchase price of the resource, exploration and development costs, and estimated restoration costs (minus any residual value). Total estimated reserves are based on geological and engineering assessments and are updated periodically as new information becomes available.

Comparison to depreciation methods

• Depletion and depreciation both allocate asset cost over useful life, but depletion is driven by physical extraction rather than time or general usage.
• Because revenue from natural resources is directly tied to extraction volume, depletion typically provides a better matching of expenses to revenues than a time-based method would.

Accounting for restoration costs

Companies in extractive industries often have legal obligations to restore the environment after extraction is complete. These costs are handled through an asset retirement obligation (ARO):

• At the time the obligation arises, the company estimates the future restoration cost and records its present value as both a liability (ARO) and an addition to the asset's carrying amount.
• The asset addition is depreciated (or depleted) over the resource's life.
• The liability is increased each period through accretion expense (essentially unwinding the discount) until it reaches the full estimated cost at the time of restoration.
• Estimates are revised periodically, with adjustments reflected in both the liability and the asset.

Depreciation for income tax purposes

MACRS depreciation system

The Modified Accelerated Cost Recovery System (MACRS) is the tax depreciation system required in the United States. It differs from book depreciation in several ways:

• Assets are assigned to specific recovery periods (3, 5, 7, 10, 15, 20, 27.5, or 39 years) based on their asset class, regardless of actual expected useful life.
• MACRS uses the declining balance method (200% for most personal property, 150% for certain property) with an automatic switch to straight-line at the optimal point.
• Salvage value is assumed to be zero under MACRS.
• A half-year convention generally applies, meaning the asset is treated as placed in service at the midpoint of the first year (a mid-quarter convention applies if more than 40% of assets are placed in service in the last quarter).

Section 179 expensing

Section 179 of the Internal Revenue Code allows businesses to immediately expense the full cost of qualifying tangible personal property in the year of purchase, up to an annual dollar limit (the limit is adjusted periodically by Congress).

• This provision is designed to encourage capital investment, particularly by smaller businesses.
• Assets expensed under Section 179 are not subject to regular MACRS depreciation since the entire cost has already been deducted.
• There are phase-out thresholds: the deduction begins to decrease dollar-for-dollar once total qualifying property placed in service exceeds a specified amount.

Temporary differences and deferred taxes

Because companies often use different depreciation methods and lives for tax versus financial reporting, temporary differences arise between taxable income and book income.

• In early years, tax depreciation (accelerated) typically exceeds book depreciation (often straight-line), creating a deferred tax liability. The company pays less tax now but will pay more later when the pattern reverses.
• In later years, book depreciation exceeds tax depreciation, and the deferred tax liability begins to reverse.
• Deferred tax amounts are calculated using the enacted tax rate expected to apply when the temporary difference reverses, and they are adjusted each period for rate changes.