Working out decline in value

UCA general rules for decline in value

UCA contain general rules for working out the decline in value of a depreciating asset, and these rules are covered in this part of the guide.

The general rules don't apply to some depreciating assets. UCA provide specific rules for working out deductions for the assets listed below:

• certain depreciating assets that cost $300 or less and that you use mainly to produce non-business assessable income, see Immediate deduction for certain non-business depreciating assets (costing $300 or less)
• certain depreciating assets that cost or are written down to less than $1,000, see Low-value pools
• in-house software that you allocate expenditure, see Software development pool
• depreciating assets you use in exploration or prospecting, see Mining and quarrying, and minerals transport
• water facilities, fencing assets, fodder storage assets and horticultural plants (including grapevines), see Primary production depreciating assets
• certain depreciating assets of primary producers, other landholders and rural land irrigation water providers you use in landcare operations
• certain depreciating assets of primary producers and other landholders you use for electricity connections or phone lines
• trees in a carbon sink forests.

There are also specific rules for working out notional deductions for depreciating assets you use in carrying on research and development activities. See, Research and development tax incentive schedule instructions 2025.

When does a depreciating asset start to decline in value?

The decline in value of a depreciating asset starts when you first use it, or install it ready for use, for any purpose, including a private purpose. This is known as a depreciating asset’s start time.

Although an asset is treated as declining in value from its start time, you can only claim a deduction for its decline in value to the extent the use is for a taxable purpose, see Definitions for UCA terms.

If you initially use a depreciating asset for a non-taxable purpose, such as for a private purpose, and in later years use it for a taxable purpose, you need to work out the asset’s decline in value from its start time, including the years it was in use for a private purpose. You can then work out your deductions for the decline in value of the asset for the years you use it for a taxable purpose, see Decline in value of a depreciating asset used for a non-taxable purpose.

Methods of working out decline in value

You generally have the choice of 2 methods to work out the decline in value of a depreciating asset. These are:

• the diminishing value method
• the prime cost method.

Both these methods are based on a depreciating asset’s effective life. For the rules to use in working out an asset’s effective life, see Effective life of a depreciating asset.

You can generally choose to use either method for each depreciating asset you hold. However, once you have chosen a method for a particular asset, you can't change to the other method for that asset.

For help with the choice and the calculations, use our Depreciation and capital allowances tool.

If you're not carrying on a business, you may be able to claim an immediate deduction for certain non-business depreciating assets (costing $300 or less).

In other cases, you don't have a choice of which method you use to work out the decline in value. These cases include:

• If you acquire intangible depreciating assets such as in-house software, certain items of intellectual property, spectrum licences and telecommunications site access rights, you must use the prime cost method.
• If you acquire a depreciating asset acquired from an associate who claims a deduction or can deduct amounts for the decline in value of the asset.
• If you acquire a depreciating asset, but the user of the asset doesn't change or is an associate of the former user – for example, under sale and leaseback arrangements.
• If there has been rollover relief.
• If the asset was allocated to a low-value pool or software development pool, calculate the decline in value at a statutory rate.

By working out the decline in value you determine the adjustable value of a depreciating asset. A depreciating asset’s adjustable value at a particular time is its cost (first and second elements) less any decline in value up to that time. For information on first and second elements of cost, see Cost of a depreciating asset. The opening adjustable value of an asset for an income year is generally the same as its adjustable value at the end of the prior income year.

You calculate the decline in value and adjustable value of a depreciating asset from the asset’s start time independently of your use of the depreciating asset for a taxable purpose. However, reduce your deduction for the decline in value by the extent that your use of the asset is for a non-taxable purpose, see Decline in value of a depreciating asset used for a non-taxable purpose. You may also need to reduce your deduction if the depreciating asset is a leisure facility or boat, even though you use the asset, or install it ready for use, for a taxable purpose, see Decline in value of leisure facilities and Decline in value of boats.

The diminishing value method

The diminishing value method:

• assumes the decline in value each income year is a constant percentage of the base value each year for the effective life of the asset
• produces a progressively smaller decline in the item’s value over time.

Depreciating assets you hold before 10 May 2006

For depreciating assets you hold before 10 May 2006, the formula for the decline in value is:

Base value multiplied by (days held divided by 365) multiplied by (150% divided by asset's effective life).

Use this formula for any asset you held before 10 May 2006, even if you dispose of it and reacquire it on or after 10 May 2006.

For depreciating assets you start to hold on or after 10 May 2006, the formula for the decline in value is:

Base value multiplied by (days held divided by 365) multiplied by (200%  divided by asset's effective life).

The base value:

• for the income year in which an asset’s start time occurs, is the asset’s cost
• for a later income year, is
  • the asset’s opening adjustable value for that year, plus
  • any amount in the asset’s second element of cost for that income year.

Days held is the number of days you hold the asset in the income year in which you either:

• use it
• install it ready for use for any purpose.

Days you hold the asset can be 366 in a leap year, even though the denominator remains 365.

For information on balancing adjustment events, see What happens if you no longer hold or use a depreciating asset?

You can't use the diminishing value method to work out the decline in value of:

• in-house software
• an item of intellectual property (except copyright in a film)
• a spectrum licence
• a telecommunications site access right.

 

The prime cost method

The prime cost method:

• assumes the value of a depreciating asset decreases constantly over its effective life
• produces a consistent decline in the item’s value over time.

The formula for the annual decline in value using the prime cost method is:

Asset's cost multiplied by (days held  divided by 365) multiplied by (100% divided by  asset's effective life)

The value of the asset's cost decreases every year by a constant amount. That constant amount is the actual cost divided by the number of years of effective life. In the first year, the value of the asset's cost is the actual cost of the asset.

If your asset cost $2,000 and has an effective life of 5 years, you can claim one fifth (20%) of its cost each year. That works out to $400 in each of the 5 years if you held the asset (and used it solely for a taxable purpose) for the whole income year.

Days held is the number of days you hold the asset in the income year in which either you:

• use it
• have it installed ready for use for any purpose.

Days held can be 366 for a leap year, even though the denominator remains 365.

For information on balancing adjustment events, such as the start and end dates, see What happens if you no longer hold or use a depreciating asset?

If there has been rollover relief and the transferor used the prime cost method to work out the asset’s decline in value, the transferee should replace the asset’s effective life in the prime cost formula with the asset’s remaining effective life, that is, any period of the asset’s effective life that is yet to elapse when the transferor stopped holding the asset, see Rollover relief.

You must use an adjusted prime cost formula if any of the following occurs:

• you recalculate the effective life of an asset, see Effective life of a depreciating asset
• you include an amount in the second element of an asset’s cost in an income year after the initial income year in which the asset’s start time occurs, see Cost of a depreciating asset
• a debt forgiveness amount reduces an asset’s opening adjustable value, see Commercial debt forgiveness
• you reduce the opening adjustable value of a depreciating asset that is the replacement asset for an asset subject to involuntary disposal
• you modify an asset’s opening adjustable value due to GST increasing or decreasing adjustments, input tax credits for the acquisition or importation of the asset, or input tax credits for amounts included in the second element of cost of an asset, see GST input tax credits
• you modify an asset’s opening adjustable value due to forex realisation gains or forex realisation losses, see Foreign currency gains and losses.

You must use the adjusted prime cost formula for the income year in which any of these changes are made (the ‘change year’) and later years:

Opening adjustable value for the change year plus any second element cost amounts for that year multiplied by (days held divided by 365) multiplied by (100% divided by asset's remaining effective life)

An asset's remaining effective life is any period of its effective life that is yet to elapse either:

• at the start of the change year
• in the case of rollover relief, when the balancing adjustment event occurs for the transferor.

You must also adjust the prime cost formula for certain intangible depreciating assets you acquire from a former holder, see Effective life of intangible depreciating assets.

Decline in value of a depreciating asset used for a non-taxable purpose

You calculate the decline in value and adjustable value of a depreciating asset from the start time independently of your use of the depreciating asset for a taxable purpose. However, you reduce your deduction for the decline in value by the extent that your use of the asset is for a non-taxable purpose.

If you initially use an asset for a non-taxable purpose, such as for a private purpose, and in later years use it for a taxable purpose, you need to work out the asset’s decline in value. The decline in value is from its start time including the years you use it for a private purpose. You can then work out your deductions for the decline in value of the asset for the years you use it for a taxable purpose.

 

Decline in value of leisure facilities

Your deduction for the decline in value of a leisure facility may be reduced even though you use it, or install it ready for use, for a taxable purpose. Your deduction is limited to the extent that either:

• the asset’s use is a fringe benefit
• the leisure facility is used (or held for use) mainly in the ordinary course of your business of providing leisure facilities for payment, to produce your assessable income in the nature of rents or similar charges, or for your employees’ use or the care of their children.

Decline in value of boats

The total amount you can claim as a deduction for using or holding a boat, including its decline in value, can't exceed your assessable income from using or holding that boat in 2024–25. If the total amount of your deduction exceeds the relevant assessable income, we reduce the deduction by the amount of the excess.

Exceptions to that reduction are any of the following:

• holding a boat as your trading stock
• using a boat (or holding it) mainly for letting it on hire in the ordinary course of a business that you carry on
• using a boat (or holding it) mainly for transporting the public or goods for payment in the ordinary course of a business that you carry on
• using a boat for a purpose that is essential to the efficient conduct of a business that you carry on.

Depreciating asset you acquire from an associate

If you acquire a depreciating asset from an associate, such as a relative or partner, and the associate has claimed or can claim deductions for the decline in value of the asset, you must use the same method of working out the decline in value as the associate.

If the associate uses the diminishing value method, you must use the same effective life they use. If they used the prime cost method, you must use any remaining period of the effective life they use.

You must recalculate the effective life of the depreciating asset if the asset’s cost increases by 10% or more in any income year, including the year in which you start to hold it, see How to recalculate effective life.

You can require the associate to tell you the method and effective life they use while holding the asset by serving a notice on them within 60 days after you acquire the asset. Penalties can be imposed if the associate intentionally refuses or fails to comply with the notice.

Sale and leaseback arrangements

If you acquire a depreciating asset but the user of the asset doesn't change or is an associate of the former user, such as under a sale and leaseback arrangement, you must use the same method of working out the decline in value as the former holder.

If the former holder uses the diminishing value method, you must use the effective life that they use. If they use the prime cost method, you must use any remaining period of the effective life they use. If you can't readily ascertain the method that the former holder was using or if they didn't use a method, you must use the diminishing value method. You must use an effective life determined by the Commissioner if you can't find out the effective life that the former holder was using or if they didn't use an effective life.

You must recalculate the effective life of the depreciating asset if the asset’s cost increases by 10% or more in any income year, including the year in which you start to hold it, see How to recalculate effective life.

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