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Diminishing Value Depreciation: What is it and How to Calculate

Diminishing value depreciation (also called the diminishing balance method) is a way of calculating how much an asset loses value over time. It’s especially useful for small business owners at tax time, because it lets you claim bigger deductions in the early years of owning an asset.

When you lodge your return with the Australian Taxation Office (ATO), this method helps accelerate expense recognition, which means you can write off more of the asset’s cost sooner.

QuickBooks makes it simple for small businesses to manage depreciation and stay tax compliant. This article will explain how diminishing value depreciation works and share the formula to calculate it. We’ll also look at alternative depreciation methods including straight-line depreciation (prime cost method) and the double declining balance method.

What is depreciation?

β€œDepreciation” is the term used to describe the gradual decrease in the value of an asset over its lifespan. It plays an important role in the financial planning of a business, including accurately assessing asset values for compliant (and potentially lower) company taxes.Β 

You can learn more here: What is Tax Depreciation? A small business owner’s guide to tax depreciation.

What is diminishing value depreciation?

Diminishing value depreciation is a method of calculating how much an asset’s value decreases over time. With this approach, you claim higher deductions in the early years of owning an asset, when it typically loses value faster, and smaller deductions in later years.

Instead of claiming the same amount each year (like in the prime cost depreciation method), the diminishing value method assumes the asset loses more value in the earlier years and less later on. So each year, you claim depreciation on the remaining value of the asset, not the original purchase price.Β 

Say, for example, you buy a laptop for $2,000:

  • In year one, you claim depreciation on the full $2,000.
  • In year two, you calculate depreciation only on what’s left of that value after the first year’s deduction.
  • The numbers keep β€œdiminishing” every year until the asset’s value is almost gone.

It’s the tax office’s way of recognising that assets usually lose value faster when they’re new, and slower as they get older.

Diminishing value depreciation formula

The ATO provides a depreciation formula for diminishing value that helps you work out exactly how much you can deduct each year. The formula is as follows:

Depreciation = Base value Γ— (days held Γ· 365) Γ— (200% Γ· asset’s effective life)

Here’s what each part means:

Base value

In the first year, this is the asset’s cost, including any expenses to install or set it up. In later years, the base value is the asset’s opening adjustable value (its cost minus any depreciation already claimed).

Days held

The number of days during the financial year that you owned the asset.

Effective life

The period the ATO says the asset can be used to generate income. You can either use the ATO’s published effective life or self-assess.

The diminishing value formula ensures your claims reflect the way assets generally decline in usefulness, giving your business a more accurate tax outcome. We’ll provide more detailed instructions for calculation in the section below.Β 

How to calculate diminishing value depreciationΒ 

The ATO’s diminishing balance depreciation formula lets you claim a larger portion of an asset’s cost in the earlier years, and smaller amounts as time goes on.

Let’s now look at an example for this formula in action:

Say you buy a piece of equipment for $10,000 on 1 July, with an effective life of 5 years:

  • Base value = $10,000
  • Days held = 365
  • Effective life = 5 years

The diminishing value depreciation calculation is as follows:

Depreciation = $10,000 Γ— (365 Γ· 365) Γ— (200% Γ· 5)

Depreciation = $10,000 Γ— 40%

Depreciation = $4,000

That means you could claim $4,000 in depreciation for the first year. Each following year, you’d use the new base value (the asset’s opening adjustable value) to recalculate.

Who should use it and when?

Diminishing value depreciation is particularly useful for businesses that own assets which lose value more quickly in the first few years of use. Choosing this method can help small businesses accelerate deductions and reflect the actual decline in an asset’s value over time.

Here are some common scenarios where diminishing value depreciation might make sense:

Scenario 1: A tradesperson buying tools and equipment

Kaitlin runs a small landscaping business and purchases a $15,000 ride-on mower.

  • In the first year, the mower is brand new and will see heavy use, meaning it loses value faster.
  • By using diminishing value depreciation, Kaitlin can claim a larger deduction upfront, reducing her taxable income for the year she bought it.
  • In subsequent years, the deductions decrease as the mower ages, reflecting its slower decline in value.

Scenario 2: An office-based business upgrading technology

Carl owns a digital marketing agency and buys $8,000 worth of new computers and software.

  • Technology assets generally lose value quickly, particularly in the first couple of years.
  • Using diminishing value depreciation allows Carl to claim more of the cost early on, helping his business manage cash flow while keeping tax deductions in line with the actual asset wear and tear.

Β Compliance with the ATO

When using diminishing value depreciation, it’s important to follow the ATO rules to ensure your claims are correct. Here are some points to keep in mind:

Use the official ATO formula

Always calculate depreciation using the ATO’s diminishing value formula:

Depreciation = Base value Γ— (days held Γ· 365) Γ— (200% Γ· asset’s effective life)

Keep accurate records

Maintain receipts and invoices for each asset. Record purchase dates, costs, residual values, and annual depreciation amounts.

Apply the correct effective life

Use either the ATO’s published effective life for the asset or a self-assessed period if justified.

Claim depreciation only on business-use assets

Assets must be used to generate income. Personal-use items cannot be depreciated.

Adjust for part-year ownership

If you buy or sell an asset partway through the financial year, calculate depreciation proportionally based on the number of days you held it.

Helpful resources:

Advantages and disadvantages

Diminishing value depreciation can be a powerful tool for small businesses, but it isn’t the right choice for every asset or situation. The table below outlines the main advantages and disadvantages of the diminishing value method to help you decide whether it suits your business needs.

Advantages

Disadvantages

Accelerates deductions

Larger tax deductions in the early years can improve cash flow.

Smaller deductions later

Deductions decrease each year, which may not suit long-term tax planning.

Reflects actual asset usage

Useful for assets that lose value faster when new, such as vehicles or technology.

More complex calculations

Takes the average of past revenue across a set period.

Reduces taxable income early

Helps new businesses manage initial expenses and reduce tax liability.

Not ideal for slow-depreciating assets

Assets that retain value longer may benefit more from straight-line depreciation.

ATO compliant

Recognised and accepted by the Australian Taxation Office for tax purposes.

Record-keeping requirements

Accurate tracking of each asset’s cost, depreciation, and remaining value is essential.

Comparison with other depreciation methods

In this section, we’ll compare the declining balance method of depreciation with two alternative methods: straight-line depreciation (prime cost method), and the double declining balance method.

Straight-line depreciation (prime cost method)

Straight-line depreciation, also known as the prime cost method, spreads the cost of an asset evenly across its useful life. Each year, the same amount is deducted as a depreciation expense, regardless of how old the asset is.

Here are the key differences of this method, compared with diminishing value depreciation:

  • Even vs accelerated deductions: Straight-line spreads deductions equally, whereas diminishing value front-loads them in the early years.
  • Cash flow impact: Diminishing value may reduce taxable income more in the early years, helping with initial cash flow, while straight-line provides a consistent deduction each year.
  • Asset types: Straight-line is often preferred for assets that lose value steadily over time (like buildings or furniture), while diminishing value suits assets that depreciate faster when new (like vehicles or technology).

Advantages

Disadvantages

Simple to calculate

Easy to understand and apply, with consistent annual deductions.

May not match actual asset usage

Doesn’t reflect faster depreciation in early years for some assets.

Predictable deductions

Good for long-term budgeting and financial planning.

Slower initial tax benefit

Fewer deductions in the early years compared with diminishing value.

Less record-keeping

No need to track net book value each year beyond basic depreciation.

May not suit high-use assets

Assets that wear out quickly may not get adequate early deductions.

ATO compliant

Accepted for tax purposes in Australia.

Potentially less cash flow advantage

Smaller early-year deductions may not help businesses needing immediate tax relief.

The table below shows the difference between diminishing value and prime cost (straight-line) depreciation, using a fictional example.Β 

Assumptions:

  • Asset cost: $10,000
  • Residual value: $0
  • Useful life: 4 years
  • Diminishing value rate: 40% (based on the ATO formula)

Year

Diminishing Value

Prime Cost (Straight-Line)

1

$4,000

$2,500

2

$2,400

$2,500

3

$1,440

$2,500

4

$864

$2,500

Total

$8,704

$10,000

Explanation:

  • Diminishing value: The deduction is higher in the first year and decreases each year as the asset’s net book value declines.
  • Prime cost (straight-line): The deduction is equal each year, giving a predictable and steady expense.

Double declining balance

Double declining balance (DDB) is an accelerated depreciation method similar to diminishing value, but it applies twice the straight-line depreciation rate to the asset’s remaining book value each year. This means deductions are even larger in the early years compared with the standard diminishing value method.

These are the key differences of the DDB method compared with the diminishing balance method:

  • Rate applied: DDB uses 200% of the straight-line rate, while the ATO’s standard diminishing value method uses a lower, specific rate.
  • Faster expense recognition: DDB front-loads depreciation even more aggressively, which can maximise early-year tax deductions.
  • Primarily used internationally: While conceptually similar, DDB is more common in US accounting, whereas Australia uses the ATO’s diminishing value method for compliance.

Year

Diminishing Value

Prime Cost (Straight-Line)

Double Declining

1

$4,000

$2,500

$5,000

2

$2,400

$2,500

$2,500

3

$1,440

$2,500

$1,250

4

$864

$2,500

$625

Total

$8,704

$10,000

$9,375

Explanation:

  • Diminishing value: Front-loads deductions, but less aggressively than DDB.
  • Prime cost (straight-line): Equal deduction each year, predictable for budgeting.
  • Double declining balance: Very high deductions in the first year, declining rapidly thereafter, maximising early-year tax benefit but leaving smaller deductions later.

Let QuickBooks help you

Depreciation is an important part of managing your business finances, helping you track the value of your assets and claim the correct deductions on your tax return. While the concept can seem complex, understanding how to apply it correctly ensures your financial statements are accurate and your tax obligations are met.

QuickBooks makes managing depreciation simple. With intuitive tools designed for small businesses, you can track assets, calculate deductions, and stay tax compliantβ€”all in one place. Make accounting easier and more efficient, so you can focus on running and growing your business.

Ready to simplify your accounting? Get started with QuickBooks today!


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