Annuity Method of Depreciation: Practical Guide for Business Success

The annuity method of depreciation treats an asset’s purchase price as an investment and factors in the interest the business loses by keeping capital locked in that asset.  Standard depreciation methods stop at wear and tear. This one goes further by recognising that purchasing an asset also means locking funds that could have earned returns elsewhere, and accounts for that cost by charging a fixed annual amount. The result presents the real economic cost of ownership, giving businesses a sharper basis for pricing long-term assets, evaluating lease-vs-buy decisions and understanding the true cost of capital-heavy investments​​​​​​​​​​​​​.

How the annuity method of depreciation works

Rather than simply spreading the purchase cost over time, the annuity method of depreciation charges a fixed annual amount, called an annuity, each year. This amount covers two things: the asset’s cost and the notional interest on the capital tied to it. Notional interest  is not an actual payment made to anyone. It is the return the business would have earned had that capital been invested elsewhere, treated as a cost of holding the asset.

The annual annuity is calculated using the following formula:

where,

• i = Interest rate ÷ 100
• TDA = Total depreciation amount
• n = Number of years (life of the asset)
• BVSY = Book value at the start of the year

Once the annuity is determined, the depreciation charge for each year is calculated as -

Depreciation = Annuity − (i × Book Value at Start of Year)

As the asset’s book value reduces over time, the interest component declines and the depreciation component increases. However, the total annual charge remains constant, which is the defining feature of this method.

This structure ensures that both the usage of the asset and the cost of capital are recognised together, making the expense more economically meaningful.

Types of annuity methods

The application of the annuity method of depreciation is based on how the annual charge is treated over the asset’s life. In practice, it is used in the following ways:

1. Fixed annuity method: The annual charge remains constant throughout the asset’s life. While the total amount stays the same each year, the interest component decreases. Thus, the depreciation component increases over time. This is the most commonly used form of the annuity method.
2. Variable annuity method: The annual charge is adjusted when there are changes in key assumptions, such as the interest rate, useful life, or additional investment in the asset. Due to its complexity and lack of consistency, this approach is less commonly used.

How to calculate depreciation using the fixed annuity method 

Let’s take an example of the fixed annuity method now and see how it supports business decision-making.

Suppose a Pune-based manufacturing firm purchases a machine for ₹5,00,000 with a useful life of 5 years and no residual value. The business applies a 10% interest rate to reflect its cost of capital.

Step 1: Calculate the annual annuity 

Annuity = 0.10 × 5,00,000 ÷ [1 − (1.10)^−5]

= 50,000 ÷ 0.3791

= ₹1,31,899 (approximately ₹1,31,900)

This amount represents the total fixed annual expense (annuity charge) that the business will recognise each year in its Profit & Loss account. This total is made up of two parts:

• Interest on the opening book value
• Depreciation (balancing figure)

To apply this year by year, the business now needs to break this fixed annuity into its two components for each period.

Step 2: Derive year-wise values

To understand how depreciation is calculated each year, remember this key relationship:

Depreciation = Annuity − Interest

• Interest is calculated on the opening book value each year.
• Depreciation becomes the balancing figure.
• The total annual charge (₹1,31,900) remains constant.

Let’s break down Year 1 to see how this works:

• Opening Value = ₹5,00,000
• Interest = 5,00,000 × 10% = ₹50,000
• Annuity = ₹1,31,900

Depreciation = 1,31,900 − 50,000 = ₹81,900

• Closing Value = 5,00,000 − 81,900 = ₹4,18,100

This same logic is applied for each subsequent year using the new opening value.

Step 3: Build the depreciation schedule

Applying the above logic year by year gives the following schedule:

This schedule shows how the same annual charge of ₹1,31,900 is maintained each year, while its composition changes.

In the early years, the interest portion is higher because the capital tied up is larger. As the asset value reduces, the interest component declines, and depreciation increases to keep the total charge constant.

For the business, this creates two advantages. First, it ensures that the cost of capital is recognised from the beginning, which improves pricing and margin decisions. Second, it provides a stable annual cost that can be easily built into financial planning and long-term projections.

Journal entries under the annuity method

Once the depreciation schedule is ready, the same numbers are recorded in the books each year. These entries ensure that both the cost of using the asset and the cost of capital are built into the business’s yearly expenses. The amounts change each year based on the schedule, but the format stays the same.

Interest on capital

(Being interest on capital locked in the asset)

This entry brings in the cost of capital tied up in the asset, which is important when the business is tracking true profitability, not just accounting profit.

Depreciation

Being depreciation charged on the asset for the year

This entry reduces the book value in line with the asset’s remaining usefulness and keeps the accounts consistent with the depreciation schedule.

How the annuity method improves business decision-making

Most depreciation methods recover an asset’s cost but say nothing about what that capital could have earned elsewhere. The annuity method fills that gap, and this changes the quality of information it produces. Some of the benefits it offers include: 

• It displays the true cost of ownership: It provides a more complete view of ownership cost by factoring in the return the business sacrifices when capital is tied up in an asset. This is particularly important for high-value, long-term investments where the cost of capital is high.

• The annual charge is fixed and predictable: It creates stability in financial planning because the total annual charge remains constant. This allows businesses to build predictable cost structures into pricing, budgeting, and long-term projections.

• It supports better investment decisions: Because the method treats the asset as a capital commitment rather than a one-time expense. This helps businesses compare alternatives such as leasing, deferring investment or reallocating capital more effectively.

• It prevents underpricing: Businesses that factor asset costs into their pricing can unknowingly undercharge when depreciation does not account for blocked capital. The annuity method corrects for this, particularly in industries where assets are central to service delivery.

Conclusion

The annuity method of depreciation is not for every asset, but for long-life investments where capital is tied up for years. It gives a clearer estimate of annual cost than simpler methods do. That accuracy matters when businesses make decisions about asset acquisition, pricing or profitability. 

Getting the method right is only half the job; maintaining clean, consistent depreciation records across asset classes is the other half, and that is where TallyPrime’s accounting features help maintain clean, consistent records, so the numbers in your books reflect the decisions you actually made.