What is depreciation? A clear guide to methods, formulas and examples

Depreciation is one of those words that appears constantly in financial statements yet rarely gets a plain explanation. This guide covers the depreciation meaning in accounting terms, walks through the main calculation methods and shows you how the numbers work with practical UK-focused examples.

What does depreciation mean?

Depreciation is the process of spreading the cost of a tangible asset over its useful life. Rather than recording the full purchase price as an expense in year one, a business allocates a portion of that cost to each accounting period the asset helps generate revenue.

Think of it this way: a delivery van does not deliver value only on the day you buy it. It works for years. Depreciation matches the cost of that van to the years it serves the business.

Depreciation in accounting vs everyday language

In everyday conversation, depreciation often means something losing value, like a car dropping in market price the moment you drive it off the forecourt. That is economic depreciation, and it reflects what a buyer would pay today.

Accounting depreciation is different. It does not attempt to track market value. Instead, it systematically allocates the original cost of an asset as an expense over time. The goal is consistency and comparability in financial reporting, not a running estimate of resale price.

Both meanings involve declining value, but the accounting version follows strict rules and formulas. When you see depreciation in a set of accounts, you are looking at the accounting definition.

Why depreciation matters for businesses

Matching costs to revenue

A core principle in accounting is matching: expenses should appear in the same period as the revenues they help produce. If a bakery buys an oven for £12,000 and uses it for 10 years, charging the full cost in year one distorts profits. Year one looks terrible; years two through 10 look artificially strong.

Depreciation smooths this out. By expensing a portion each year, the financial statements give a fairer picture of performance. This matters to owners, investors, lenders and anyone else relying on those numbers for decisions.

Accumulated depreciation on the balance sheet

Each year, the depreciation expense appears on the profit and loss statement. Meanwhile, the running total of all depreciation charged since the asset was purchased sits on the balance sheet under accumulated depreciation.

Accumulated depreciation is a contra-asset account. It reduces the gross value of fixed assets to show their net book value, sometimes called carrying value. If that oven cost £12,000 and three years of depreciation total £3,600, the net book value is £8,400.

Common types of depreciation methods

Businesses choose a depreciation method based on the nature of the asset and how its economic benefits are consumed. UK accounting standards permit several approaches, and consistency is key once a method is selected.

Straight line method of depreciation

The straight line method of depreciation is the simplest and most widely used. It allocates an equal amount of depreciation to each year of the asset’s useful life.

This method suits assets that deliver roughly constant benefits over time, such as office furniture or buildings. Its predictability also makes budgeting easier.

Reducing balance method of depreciation

The reducing balance method, sometimes called the diminishing balance method, applies a fixed percentage to the remaining book value each year. Early years see higher depreciation charges, which taper off as the asset ages.

This approach fits assets that lose efficiency quickly or become technologically outdated, such as computers or vehicles. It front-loads the expense, reflecting the faster decline in usefulness.

Other methods (Units of production, sum-of-years digits)

Units of production depreciation ties the expense directly to usage. A printing press might be depreciated based on the number of pages printed rather than years owned. This method suits assets whose wear depends heavily on output.

Sum-of-years digits is an accelerated method that, like reducing balance, loads more expense into early years but follows a different formula based on the remaining useful life each period. It is less common in UK practice but appears in some international contexts.

How to calculate depreciation: Formulas and examples

Straight line depreciation formula

The depreciation formula for the straight line method is:

Annual Depreciation = (Cost - Residual Value) / Useful Life

Cost is the original purchase price plus any costs to bring the asset into use. Residual value, sometimes called salvage value, is the estimated amount the asset will be worth at the end of its useful life. Useful life is the number of years you expect the asset to serve the business.

Reducing balance depreciation formula

For the reducing balance method:

Annual Depreciation = Book Value at Start of Year x Depreciation Rate

The depreciation rate is a fixed percentage chosen by the business. Book value at the start of each year is the original cost minus accumulated depreciation to date.

Worked example with UK context

Suppose a UK marketing agency buys computer equipment for £8,000. The agency estimates a useful life of four years and a residual value of £800. Management must decide how to calculate depreciation.

Straight line calculation:

Annual Depreciation = (8,000 - 800) / 4 = £1,800 per year

Reducing balance calculation at 40%:

In year four of the reducing balance example, the calculated figure would be £691, but to reach the residual value of £800, the final charge is adjusted.

Key terms explained

What is accumulated depreciation?

Accumulated depreciation is the total depreciation charged against an asset since it was purchased. It grows each year by the amount of the current period’s depreciation expense.

On the balance sheet, accumulated depreciation appears as a deduction from the gross value of fixed assets. This presentation shows readers both the original investment and how much has been expensed to date.

Depreciation expense vs asset value

Depreciation expense is the portion of an asset’s cost recognised in the profit and loss statement for a single period. It reduces reported profit for that year.

Asset value, specifically net book value, is the figure on the balance sheet showing original cost minus accumulated depreciation. It does not represent market value or replacement cost.

Understanding this distinction prevents a common error: assuming net book value equals what an asset could sell for. The two figures may differ significantly.

Depreciation and UK tax considerations

Capital allowances vs accounting depreciation

In the UK, depreciation charged in the accounts is not deductible for corporation tax purposes. Instead, HMRC uses a separate system called capital allowances to give tax relief on qualifying capital expenditure.

Capital allowances have their own rules and rates, which may differ from the depreciation policy a business chooses for its financial statements. For example, as of April 2026, the Annual Investment Allowance may allow 100% relief on qualifying plant and machinery up to the prevailing limit (check HMRC for the current threshold).

Because capital allowances and accounting depreciation rarely match, businesses make adjustments when calculating taxable profit. The depreciation expense is added back, and the capital allowance is deducted.

This is a complex area. Specific circumstances vary, and HMRC rules change. Consulting a qualified accountant or tax adviser is the prudent step before making decisions based on expected tax relief.

Summary

Depreciation allocates the cost of a tangible asset over its useful life, helping financial statements reflect an estimated allocation of cost across periods. It is a non-cash expense, meaning no money leaves the business when it is recorded, yet it shapes reported profit and asset values.

The straight line method spreads the cost evenly, while the reducing balance method front-loads the expense. Other approaches, such as units of production, tie depreciation to actual usage. Choosing a method depends on how the asset delivers its benefits.

Accumulated depreciation accumulates on the balance sheet, reducing gross asset value to net book value. This figure differs from market value, a point worth remembering when interpreting accounts.

For UK businesses, accounting depreciation does not directly reduce the tax bill. Capital allowances serve that purpose, and the two systems operate independently. Professional advice is advisable to navigate the specifics.

By understanding the depreciation formula, types of depreciation and the role of accumulated depreciation, you gain a clearer view of how businesses track and report the cost of their physical assets over time.