Estimate straight-line or declining-balance depreciation for business and accounting planning.
This tool provides estimates for informational purposes only. It is not a substitute for professional advice. Individual results vary based on your inputs and assumptions, so review important decisions with a qualified professional.
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Depreciation is the systematic allocation of an asset's cost over its useful life. Rather than expensing the full cost of a long-lived asset in the year of purchase, depreciation spreads the expense across the periods in which the asset provides economic benefit. This principle – matching expenses to the revenues they help generate – is fundamental to accrual-basis accounting under both US GAAP and UK IFRS/FRS 102. Depreciation reduces reported profit, reduces taxable income (in many cases), and appears on the balance sheet as accumulated depreciation, reducing the asset's carrying (book) value.
Depreciation is relevant for businesses of all sizes: sole traders in the UK claiming capital allowances, US small businesses using Section 179, large corporations managing fleets of vehicles, and real estate investors depreciating rental properties over decades. Understanding the different methods allows you to choose the approach that best matches your assets' actual wear and tear and maximises your legitimate tax benefit.
Straight-line (SL) depreciation is the simplest and most widely used method. It allocates an equal amount of depreciation expense each year across the asset's useful life. The formula is:
Annual Depreciation = (Cost – Salvage Value) / Useful Life in Years
For example, a machine costing £50,000 with a £5,000 salvage value and a 10-year useful life produces annual depreciation of (£50,000 – £5,000) / 10 = £4,500 per year. The asset's book value falls from £50,000 to £5,000 in equal £4,500 increments each year. Straight-line is ideal for assets that produce consistent economic benefit over time, such as buildings, furniture, and long-lived equipment.
The declining balance (DB) method applies a fixed percentage rate to the asset's remaining book value each year, producing a front-loaded depreciation pattern. Because the rate is applied to a diminishing base, the annual depreciation charge decreases over time. The formula is:
Annual Depreciation = Book Value at Start of Year × Depreciation Rate
A common rate is 20% or 25%. For an asset with a £30,000 initial cost: Year 1 = £30,000 × 20% = £6,000; Year 2 = £24,000 × 20% = £4,800; Year 3 = £19,200 × 20% = £3,840, and so on. This pattern often better matches assets like vehicles or technology that lose value rapidly early in their life. UK capital allowances (Writing Down Allowances) use a declining balance approach.
Double declining balance (DDB) uses twice the straight-line rate applied to the remaining book value. If the straight-line rate for a 5-year asset is 20%, DDB uses 40%. The formula is:
Annual Depreciation = (2 / Useful Life) × Book Value at Start of Year
DDB is particularly aggressive in early years, making it useful for tax planning when accelerated deductions are beneficial. Most implementations switch to straight-line when straight-line becomes larger, to fully depreciate the asset to salvage value.
Sum-of-years-digits (SYD) is another accelerated method. For a 5-year asset, the digits 1+2+3+4+5 = 15. Year 1 uses the fraction 5/15, Year 2 uses 4/15, and so on down to Year 5 which uses 1/15. The depreciable base is cost minus salvage value. SYD front-loads depreciation like DDB but with a smoother curve, and is sometimes preferred in accounting for assets with a clearly declining useful contribution.
For US federal income tax purposes, the IRS requires most tangible property to be depreciated using MACRS (Modified Accelerated Cost Recovery System), introduced by the Tax Reform Act of 1986. MACRS ignores salvage value entirely and uses statutory recovery periods and methods:
| Asset Class | Recovery Period | Method | Examples |
|---|---|---|---|
| 3-year property | 3 years | 200% DB | Tractor units, racehorses |
| 5-year property | 5 years | 200% DB | Cars, computers, light trucks |
| 7-year property | 7 years | 200% DB | Office furniture, most equipment |
| 15-year property | 15 years | 150% DB | Land improvements, restaurants |
| 27.5-year property | 27.5 years | Straight-line | Residential rental property |
| 39-year property | 39 years | Straight-line | Commercial real estate |
MACRS also applies the half-year convention for most property (treating all assets as if placed in service mid-year) or the mid-quarter convention if more than 40% of assets are placed in service in Q4.
Section 179 of the US Internal Revenue Code allows businesses to immediately expense (deduct in full) the cost of qualifying property in the year of purchase, up to an annual limit of $1,160,000 for 2023 (indexed for inflation). The deduction phases out dollar-for-dollar when total equipment purchases exceed $2,890,000. Section 179 applies to machinery, equipment, vehicles (with limits), and certain software and qualified improvement property. It cannot create a business loss.
Bonus depreciation (also called additional first-year depreciation) allows an immediate percentage deduction on new and used qualifying property. Following the Tax Cuts and Jobs Act (TCJA), 100% bonus depreciation applied from 2018-2022. It phases down: 80% in 2023, 60% in 2024, 40% in 2025, 20% in 2026, and 0% from 2027 (unless extended by Congress). Unlike Section 179, bonus depreciation can create a loss.
In the UK, businesses do not use standard accounting depreciation for tax purposes. Instead, HMRC uses a parallel system called Capital Allowances. Key components include:
Annual Investment Allowance (AIA): Provides 100% first-year deduction on qualifying plant and machinery up to £1,000,000 per year (since January 2022 permanently). This is extremely generous and means most SMEs can fully deduct equipment purchases in the year of purchase.
Writing Down Allowance (WDA) – Main Pool: 18% per year on a declining balance basis for most plant and machinery not covered by AIA. Assets are pooled together rather than depreciated individually, with the pool balance reducing by 18% each year.
Writing Down Allowance – Special Rate Pool: 6% per year on a declining balance basis for integral features (electrical systems, cold water systems, heating), long-life assets (over 25 years economic life), and certain cars with high CO2 emissions.
First Year Allowances (FYA): 100% in year one for qualifying assets, including zero-emission cars and energy-efficient equipment.
Importantly, UK commercial property and most residential property does not qualify for capital allowances (unlike US MACRS for buildings). Businesses cannot claim capital allowances on land.
Vehicles are among the most commonly depreciated assets. New cars typically lose 15-25% of their value in the first year and continue declining at 15-20% per year for the following two to three years. A car bought for £30,000 new might be worth £22,500 after one year, £17,000 after two years, and £13,000 after three years – representing a total depreciation of £17,000 (57%) in just three years. For US tax purposes, the IRS limits luxury automobile depreciation under Section 280F, with caps of approximately $12,200 in year one for passenger vehicles placed in service in 2023 (before bonus depreciation).
An important distinction exists between depreciation for accounting purposes (book depreciation, used in financial statements) and depreciation for tax purposes (tax depreciation, used in tax returns). These often differ significantly. A company might use straight-line depreciation over 10 years in its financial statements while using MACRS 5-year DDB for the same asset on its tax return. The difference creates deferred tax liabilities (or assets) on the balance sheet. Understanding both systems is essential for accurate financial reporting and tax planning.
The straight-line depreciation formula is: Annual Depreciation = (Cost – Salvage Value) / Useful Life in Years. For a £20,000 machine with £2,000 salvage value and 9-year useful life, annual depreciation = (£20,000 – £2,000) / 9 = £2,000 per year. The asset's book value decreases by £2,000 each year until it reaches the £2,000 salvage value at the end of year 9.
MACRS (Modified Accelerated Cost Recovery System) is the US tax depreciation system required by the IRS for most business property placed in service after 1986. It uses predetermined recovery periods (3, 5, 7, 15, 27.5, or 39 years depending on asset type) and specified methods (200% declining balance for most personal property, straight-line for real estate). MACRS ignores salvage value and applies the half-year convention in most cases. It is used exclusively for US federal income tax calculations, not for financial statement accounting.
UK capital allowances replace standard accounting depreciation for tax purposes. The Annual Investment Allowance (AIA) allows 100% first-year deduction on qualifying plant and machinery up to £1,000,000 per year. Above that limit, assets go into pools: the main pool with 18% Writing Down Allowance per year (declining balance), or the special rate pool at 6% per year. Businesses claim capital allowances on their self-assessment or corporation tax return to reduce taxable profits.
Both Section 179 and bonus depreciation allow immediate expensing of business assets in the US. Section 179 has an annual deduction limit ($1,160,000 in 2023), phases out for large buyers, and cannot create a loss. Bonus depreciation has no dollar cap, can create or increase a net operating loss, and applies a declining percentage (60% in 2024, 40% in 2025, 20% in 2026). Businesses often use Section 179 first, then bonus depreciation for remaining costs.
For UK tax purposes, cars are generally excluded from the Annual Investment Allowance and must be claimed through Writing Down Allowances. Cars with CO2 emissions of 50g/km or less qualify for a 100% first-year allowance. Cars with CO2 emissions of 51-110g/km go in the main pool at 18% WDA. Cars emitting more than 110g/km go in the special rate pool at 6% WDA. Each car is tracked individually (not pooled) when sold, with balancing adjustments on disposal.
Yes. US residential rental property is depreciated over 27.5 years using the straight-line method under MACRS. Only the building value (not land) is depreciable. For a property purchased at $350,000 with land worth $50,000, the depreciable basis is $300,000. Annual depreciation = $300,000 / 27.5 = approximately $10,909 per year. This depreciation deduction can significantly reduce rental income tax. On sale, depreciation recapture is taxed at 25%.
Salvage value (also called residual value) is the estimated value of an asset at the end of its useful life. It reduces the depreciable base in straight-line and sum-of-years-digits calculations. Declining balance methods may not automatically stop at salvage value (requiring a switch to straight-line). MACRS ignores salvage value entirely for US tax purposes. In UK GAAP and IFRS, salvage value must be estimated and deducted from cost before calculating depreciation.
Depreciation applies to tangible assets (machinery, vehicles, buildings). Amortisation applies to intangible assets (patents, trademarks, goodwill, software licences). Both spread the cost of an asset over its useful life, and both reduce taxable income where applicable. In the US, Section 197 intangibles (goodwill, customer lists, patents acquired with a business) are amortised over 15 years for tax purposes. In the UK, HMRC has specific rules for intangible asset relief, generally allowing amortisation to match the accounting charge.