Accountancy · Ch 7 — Depreciation, Provisions and Reserves
Estimated Useful Life
Estimated Useful Life
The Core Idea: Useful Life vs. Physical Life
Depreciation is not about wearing out until the asset breaks. It is about using up the asset's economic value. That is why the concept of useful life exists. Useful life is the period over which an asset is expected to generate revenue for the business. An asset may still be physically present — it may still run, still look fine — but if it can no longer produce goods or services at a profit, its useful life is over.
The textbook gives a clear example: a machine purchased for production is estimated to work well for 5 years. After 5 years, the machine is still in good physical condition. But if you try to run it, the cost of production becomes too high — it is no longer commercially viable. So the useful life is 5 years, not the physical life of, say, 10 or 15 years.
Useful life is the economic or commercial life of an asset. Physical life is irrelevant for depreciation. The asset may exist physically but be useless for profitable production.
How Useful Life is Defined by Accounting Standard – 6
As per Accounting Standard – 6 (now superseded by Ind AS 16, but the principle remains the same for Class 11), useful life is:
"the period over which it is expected to be used by the enterprise."
Notice the word used. It is not "the period over which it exists." It is the period the business intends and expects to keep the asset in productive use.
Units for Expressing Useful Life
Useful life is most commonly expressed in number of years. But that is not the only way. The textbook mentions two other units:
- Number of units of output — for example, a mine may have a useful life of 10,00,000 tonnes of ore extracted, not a fixed number of years.
- Number of working hours — for example, a machine may be expected to run for 20,000 working hours.
This matters because the depreciation method you choose (like the Units of Production method) depends on how useful life is defined.
Factors That Determine Useful Life
The textbook lists six factors. Each one can shorten or lengthen the useful life estimate.
| Factor | Explanation |
|---|---|
| Legal or contractual limits | A leasehold asset has a useful life equal to the lease period. You cannot use it beyond the lease term, even if it is still in good condition. |
| Number of shifts | An asset used in a three-shift operation wears out faster than one used in a single shift. Useful life is shorter with higher usage intensity. |
| Repair and maintenance policy | Good maintenance can extend useful life. Poor maintenance shortens it. |
| Technological obsolescence | A machine may be physically fine, but a newer, more efficient machine makes it obsolete. Useful life ends when technology moves ahead. |
| Innovation/improvement in production method | Similar to obsolescence — if a better production method arrives, the old asset may no longer be useful. |
| Legal or other restrictions | Government regulations, environmental laws, or safety standards may force an asset out of use before its physical life ends. |
Useful life is an estimate. It is not a certainty. The business must use its best judgment based on experience, industry practice, and the factors listed above.
The General Rule
Normally, useful life is shorter than physical life. That is the key takeaway. Depreciation is calculated over the useful life, not the physical life. If you mistakenly use physical life, you will understate depreciation in the early years and overstate profits.