Depreciation Methods – Straight-Line, Units of Production, and Declining Balance

Depreciation is the systematic allocation of the cost of a tangible fixed asset over its useful life. It reflects the consumption of economic benefits as the asset is used in operations. The method chosen affects reported income, asset balances, and financial ratios.

This article outlines the major depreciation methods used under U.S. GAAP (ASC 360) and IFRS (IAS 16), including straight-line, units of production, and declining balance. Key assumptions, calculations, and in-text journal entries are included.

1. Depreciation Basics

To compute depreciation, the following elements must be determined:

✦ Cost of the asset

✦ Useful life – estimated period of economic benefit

✦ Residual (salvage) value – expected value at end of useful life

✦ Depreciation method – reflects pattern of asset usage

Depreciable base = Cost – Residual Value

Once determined, depreciation expense is recorded consistently over the asset's useful life.

2. Straight-Line Method

The straight-line method allocates an equal amount of depreciation expense to each year of the asset’s life.

✦ Most common and simplest method

✦ Suitable for assets with uniform usage

✦ Results in constant annual expense

Formula: (Cost – Residual Value) ÷ Useful Life

Example: ✦ Cost = $100,000 ✦ Residual = $10,000 ✦ Useful life = 5 years ✦ Annual depreciation = ($100,000 – $10,000) ÷ 5 = $18,000

To record annual expense: Dr. Depreciation Expense – $18,000 / Cr. Accumulated Depreciation – $18,000.

3. Units of Production Method

This method ties depreciation to actual usage or output instead of time.

✦ Best for equipment where wear and tear depends on usage

✦ Requires estimation of total expected production

Formula: (Cost – Residual Value) ÷ Total Estimated Output × Actual Output

Example: ✦ Cost = $120,000 ✦ Residual = $20,000 ✦ Estimated output = 100,000 units ✦ This year’s output = 25,000 units ✦ Depreciation = ($120,000 – $20,000) ÷ 100,000 × 25,000 = $25,000

Dr. Depreciation Expense – $25,000 / Cr. Accumulated Depreciation – $25,000.

Units of production is generally not acceptable for buildings or intangibles.

4. Declining Balance Method

The declining balance method accelerates depreciation, resulting in higher expense in early years and lower in later years.

✦ Matches depreciation to declining productivity or revenue

✦ Common version: Double Declining Balance (DDB) ✦ Does not subtract residual value when calculating annual expense

Formula (DDB): 2 × Straight-Line Rate × Book Value at Beginning of Year

Example: ✦ Cost = $100,000 ✦ Useful life = 5 years ✦ Year 1 depreciation = 2 × 20% × $100,000 = $40,000 ✦ Year 2 depreciation = 2 × 20% × ($100,000 – $40,000) = $24,000

Year 1 entry: Dr. Depreciation Expense – $40,000 / Cr. Accumulated Depreciation – $40,000.

This method cannot reduce book value below the residual value.

5. Method Selection and Changes

The method chosen should reflect the pattern of economic benefit consumption.

✦ GAAP and IFRS require review of method and useful life periodically

✦ A change in method is treated as a change in estimate, applied prospectively

To switch from straight-line to units of production in Year 3: no retrospective adjustment required.

6. Disclosure Requirements

Financial statements must disclose:

✦ Depreciation methods used for each class of PP&E

✦ Useful lives or depreciation rates applied

✦ Accumulated depreciation and gross carrying amount

✦ Reconciliation of PP&E balances by category

Balance sheet example: ✦ Equipment – $300,000 ✦ Less: Accumulated Depreciation – ($120,000) ✦ Net Equipment – $180,000