What Is Depreciation — and Why Can't I Always Claim an Asset Immediately?

Because the equipment isn't used up in one year — it keeps producing value for the business over several years. Depreciation spreads the tax deduction for an asset's cost across its useful life, rather than claiming the whole amount the moment you pay for it. It's the tax system's way of matching the deduction to when the asset is actually being used to earn income.

An ordinary running expense — rent, wages, a stationery order — is entirely consumed within the period it's paid for, so it's fully deductible immediately. An asset like a vehicle, a piece of machinery or office equipment isn't consumed that way — it keeps working for the business over several years. Depreciation reflects that reality by spreading the deduction across the years the asset genuinely contributes to earning income, rather than distorting a single year's result with the full cost upfront.

• Effective life. Each type of asset has an estimated useful life — how long it's expected to remain productive — which the ATO publishes guidance on, or which can be self-assessed in some cases.

• Decline in value. The asset's cost is spread across that effective life, using either the diminishing value method (larger deductions earlier) or the prime cost method (equal deductions each year).

• Small business pooling. Small businesses can generally use simplified rules, pooling eligible assets together and depreciating the pool at set annual rates — 15% in the first year and 30% each year after, for the general small business pool.

The total deduction over time is the same either way — what changes is when it's recognised, which is exactly the point. Depreciation gives a more accurate picture of profit in any single year, rather than one year absorbing the full cost of an asset that will keep working for years to come.

Understanding depreciation also helps explain a pattern covered elsewhere in the Knowledge Centre: why a large equipment purchase can hit your bank balance immediately but only show up gradually in your P&L. That gap between cash moving and profit being recognised is exactly what depreciation creates — deliberately, and for good reason.

For many small businesses, the instant asset write-off allows an asset below a certain cost threshold to be deducted in full immediately, rather than depreciated over several years — this is covered in detail in its own guide, since it changes the calculation considerably for most day-to-day equipment purchases.

• Do I understand why a large asset purchase doesn't produce an equally large deduction in the same year?

• Am I aware of which depreciation method — or pooling approach — applies to my business?

• Have I checked whether a given purchase might qualify for the instant asset write-off instead?

• Do I understand the difference between cash leaving the business and the expense being recognised for tax purposes?

• you're not sure which depreciation method or pooling approach applies to your business;

• you're planning a significant asset purchase and want to understand the tax timing before you buy;

• you want to check whether a specific asset would qualify for the instant asset write-off instead; or

• your asset register hasn't been reviewed in a while and you want to confirm it's accurate.

→ Instant Asset Write-Off — What Is It and When Can My Business Use It?

→ My Business Is Making a Profit — So Why Is There No Money in the Bank?

→ Repairs vs Improvements — Why Does the Difference Matter for Tax?

SKC Accounting | Knowledge Centre | Knowledge Guide 060

Last reviewed: August 2026

General information only. This guide does not take into account your individual circumstances and is not a substitute for professional accounting, taxation, legal or financial advice.