What does depreciation do in accounting?
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Accounting · Foundations
Depreciation
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Depreciation The accounting practice of spreading a long-lived asset's cost over the years it is used, instead of charging the full cost in the purchase year. Full entry → spreads the cost of a long-lived asset, like a delivery van or a piece of machinery, over the years it serves the business, instead of charging the whole price in the purchase year. Each year, part of the cost becomes an expense, matched to the revenue the asset helps earn. The Straight-line method The simplest depreciation method: cost minus salvage value divided by useful life, giving the same expense every year. Full entry → charges an equal amount every year: cost minus Salvage value The estimated amount an asset will be worth, as a sale or trade-in, when its useful life ends; also called residual value. Full entry →, divided by Useful life The length of time a business expects to use an asset productively before it is worn out or obsolete. Full entry →.
Why this matters
Depreciation sits behind the numbers of almost every business that owns equipment, vehicles, or buildings. It keeps one year's income statement from being crushed by a big purchase, and it keeps the balance sheet honest about how much of an asset's cost is still waiting to be used up. Understanding the idea lets you read terms like Book value An asset's original cost minus the depreciation taken on it so far, also called net book value. Full entry →, Accumulated depreciation The running total of all depreciation expense charged on an asset since it was bought. Full entry →, and net income with real comprehension. It also sets you up for later topics, from adjusting entries and financial statements to the difference between accounting rules and tax rules, where the same spreading idea keeps showing up.
The college version
What depreciation is
Depreciation is the accounting practice of spreading the cost of a long-lived asset over the periods it serves, rather than treating the full purchase price as an expense of a single year. A delivery van that will carry goods for five years is not "used up" in the year it is bought: it keeps producing benefit year after year, so accountants spread its cost across those years. The amount spread each period is the depreciation expense, reported on the income statement. The part of the cost not yet spread remains on the balance sheet as the asset's book value, alongside accumulated depreciation, the running total of the expense taken so far.
Why it exists: the matching idea
Depreciation exists because of matching: costs should be reported in the same periods as the revenue they help generate. If a bakery bought a $30,000 van and charged the entire amount in the purchase year, that year's income statement would show a huge expense and every later year would show none, even though the van helps earn delivery revenue in all of them. Spreading the cost puts a fair slice of expense in each year of service, so profits are not distorted by the timing of big purchases. This is part of the broader accrual-accounting approach, where revenue and expenses are recorded when they are earned and incurred, not only when cash changes hands.
The straight-line method
The straight-line method is the simplest and most widely used way to spread an asset's cost, and it is the one to master first. It charges the same dollar amount of depreciation every year. Three pieces of information go in: the asset's cost, its salvage value (the estimated amount it will be worth, as a sale or trade-in, when its useful life ends), and its useful life (how long the business expects to use it productively). The formula is: (cost − salvage value) ÷ useful life. For a van that cost $30,000, will be worth $5,000 after five years, the Depreciable base The portion of an asset's cost that gets spread into expense: the cost minus the salvage value. Full entry → is $30,000 − $5,000 = $25,000, and the annual expense is $25,000 ÷ 5 = $5,000. The same $5,000 appears as an expense each year, and the van's book value falls by $5,000 each year: $25,000 after year one, $20,000 after year two, and so on, down to the $5,000 salvage value.
Other methods, book value, and market value
Two other common methods deserve a mention. Declining balance charges more depreciation in the early years and less later, which suits assets that lose usefulness quickly. Units of production charges depreciation based on how much the asset is actually used, such as miles driven or units made. Both spread the same total cost; only the timing differs. A separate idea matters more for reading statements: book value is the un-depreciated portion of original cost, not a guess at what the asset could sell for. Depreciation is a spreading rule, and the calculation is not based on changes in the asset's Market value The price an asset could actually be sold for today, which can differ from its book value. Full entry →. A van with a $15,000 book value might sell for $12,000 or $18,000 on the open market; the accounts do not chase that number.
Depreciation and taxes, plus the honest framing
The depreciation a company reports in its financial statements is book depreciation, computed under accounting rules. The depreciation it claims on its tax return is tax depreciation, computed under tax rules, which in the United States follow a separate system called MACRS. The two are different numbers for the same asset, and that is expected; nothing in this lesson is tax advice. The honest framing to carry away: depreciation is a spreading rule, not a valuation. It decides when a cost shows up in the income statement; it does not say what an asset is worth today, and it does not put cash aside for a replacement. Two related details follow from the definition: land is never depreciated, because it is assumed to have an unlimited useful life, and a fully depreciated asset stays on the books at its salvage value until it is sold or scrapped.
Eli explains
The same idea, in plain words
Explain it like I’m 10
When a business buys something that will last for years, a van, a machine, a building, it does not treat the whole purchase as an expense of just one year. The van will help earn money for five years, so its cost is spread over five years. That spreading is depreciation. The straight-line method is the simplest version: figure out how much of the cost will be used up (cost minus what it will still be worth at the end), then divide by the number of years. Same amount every year, like a steady monthly payment the asset makes to the income statement.
Picture it like this
Think of a shop that buys a year's supply of 120 boxes of packing tape at once. It would not call the whole delivery an expense of that single day. It counts a few boxes each month as they are used. Depreciation does the same for a van: the van is a box of usefulness that gets consumed a little each year, and each year's slice becomes that year's expense.
Where the picture stops working
The tape-box analogy suggests the asset is used up at a perfectly steady rate. Real assets often lose usefulness unevenly, and straight-line ignores that by design, which is why other methods exist. The analogy also implies physical wear, but depreciation is about spreading recorded cost, not measuring wear, and it never sets aside cash for a replacement.
Worked example
Bella's Bakery buys a delivery van for $30,000. The van is expected to serve deliveries for five years, after which Bella estimates it can be sold for $5,000. The depreciable base is $30,000 − $5,000 = $25,000. Straight-line depreciation: $25,000 ÷ 5 = $5,000 per year. After year one, the income statement shows $5,000 of depreciation expense, accumulated depreciation is $5,000, and the van's book value is $30,000 − $5,000 = $25,000. After year three, accumulated depreciation is $15,000 and book value is $15,000. At the end of year five the van is fully depreciated to its $5,000 salvage value. Each year's $5,000 slice is matched to the delivery revenue the van helped earn.
Key takeaway
Depreciation is a spreading rule, not a valuation: it moves a long-lived asset's cost into expense over its useful life. The straight-line method divides cost minus salvage value by the years of service.
Quick check
3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.
Why does a business spread an asset's cost over several years instead of charging the full cost in the purchase year?
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Bella's Bakery buys a delivery van for $30,000. It will last 5 years and be worth $5,000 at the end. Using straight-line depreciation, what is the annual depreciation expense?
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Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related
You’ll learn to
- Define depreciation as spreading the cost of a long-lived asset over its useful life.
- Explain why depreciation exists: an asset serves many periods, so its cost is matched to the revenue it helps produce.
- Apply the straight-line method to compute annual depreciation, accumulated depreciation, and book value with simple arithmetic.
- Distinguish book value from market value, and book depreciation from tax depreciation.
- Analyze common depreciation mistakes, such as treating depreciation as cash set aside or as a market-value adjustment.
Common mistakes
Thinking depreciation measures how much an asset's market value has dropped.
Depreciation is a cost-spreading rule, not a valuation. Book value is the un-depreciated part of original cost, not what the asset would sell for.
Forgetting to subtract salvage value in the straight-line formula.
Only the depreciable base, cost minus salvage, is spread into expense; the salvage value is expected to remain at the end of the asset's life.
Believing depreciation sets aside cash to replace the asset.
Depreciation is a bookkeeping allocation; no cash moves when it is recorded, and it does not create a cash fund.
Confusing one year's depreciation with accumulated depreciation.
Annual depreciation is a single year's slice; accumulated depreciation is the running total since purchase, and it is the number subtracted from cost to get book value.
Depreciating land along with the building on it.
Land is not depreciated, because it is assumed to have an unlimited useful life; only the building wears out over a measurable life.
Easily confused
Book value vs. Market value
Book value is the un-depreciated portion of original cost; market value is what the asset could sell for today. They measure different things and usually differ.
Straight-line depreciation vs. Declining-balance depreciation
Straight-line charges the same amount each year; declining balance charges more in the early years and less later. Both spread the same total cost, just on different schedules.
Book depreciation vs. Tax depreciation
Book depreciation follows accounting rules and appears in financial statements; tax depreciation follows tax rules, such as MACRS in the United States, and is used on tax returns.
Key vocabulary
- Depreciation
- The accounting practice of spreading a long-lived asset's cost over the years it is used, instead of charging the full cost in the purchase year.
- Useful life
- The length of time a business expects to use an asset productively before it is worn out or obsolete.
- Salvage value
- The estimated amount an asset will be worth, as a sale or trade-in, when its useful life ends; also called residual value.
- Straight-line method
- The simplest depreciation method: cost minus salvage value divided by useful life, giving the same expense every year.
- Depreciable base
- The portion of an asset's cost that gets spread into expense: the cost minus the salvage value.
- Book value
- An asset's original cost minus the depreciation taken on it so far, also called net book value.
- Accumulated depreciation
- The running total of all depreciation expense charged on an asset since it was bought.
- Market value
- The price an asset could actually be sold for today, which can differ from its book value.
Sources & references
- Principles of Accounting, Volume 1: Financial Accounting, Section 11.3: Explain and Apply Depreciation Methods to Allocate Capitalized Costs — OpenStax, Rice University
- Depreciation Expense — Overview and When to Use Various Types — Corporate Finance Institute (CFI)
- MACRS Depreciation — Definition, How It Works, Methods — Corporate Finance Institute (CFI)
EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.
Researched 2026-08-21
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