Key Points
- IAS 16.43 requires separate depreciation of each part of an item of PP&E with a cost that is significant relative to the total cost of the item.
- Parts with similar useful lives and consumption patterns may be grouped and depreciated as a single component.
- A building with a 40-year structural shell and a 15-year HVAC system produces materially different annual charges if componentised versus treated as one asset.
- Failing to componentise is one of the most common fixed-asset findings in European regulatory inspections.
What is Component Depreciation?
IAS 16.43 states that when a part of an item of PP&E has a cost that is significant in relation to the total cost of the item, that part is depreciated separately. A production facility might contain a structural frame, mechanical systems, electrical installations, and a roof. Each has a different expected useful life. Depreciating the entire facility over a single blended life misstates the charge in every period because some components are consumed faster than others.
IAS 16.45 allows grouping of parts with the same useful life and the same depreciation method. This keeps the fixed-asset register practical without sacrificing accuracy. The standard also permits (IAS 16.44) separating a part that does not have a cost that is individually significant, if the entity judges that separate depreciation provides a more faithful representation. In practice, the question audit teams face is where to draw the significance line. There is no bright-line threshold in the standard itself, so most firms apply a percentage of total asset cost (often 10% to 20%) as an internal policy and document the rationale.
ISA 540.13(a) requires the auditor to evaluate whether the entity's estimation method is appropriate. For component depreciation that means verifying the entity identified the right components, assigned supportable useful lives to each, and documented why groupings (if any) are reasonable. When the entity replaces a component (a new roof on an existing building, for example), IAS 16.70 requires derecognition of the old component's carrying amount. Missing this derecognition is where the accounting error typically compounds.
Worked example
Client: Italian food production company, FY2025, revenue EUR 67M, IFRS reporter. Rossi completes a new cold-storage warehouse on 1 January 2025 for a total cost of EUR 4.8M. The project engineer's completion certificate identifies four significant components.
| Component | Cost (EUR) | Useful life | Method |
|---|---|---|---|
| Structural shell | 2,400,000 | 40 years | Straight-line |
| Refrigeration plant | 1,200,000 | 12 years | Straight-line |
| Insulated panel cladding | 720,000 | 20 years | Straight-line |
| Electrical and control systems | 480,000 | 10 years | Straight-line |
Residual value for all components is estimated at nil (cold-storage components have negligible resale value at the end of their individual lives).
Step 1 — Identify components and assess significance
Each component exceeds 10% of total cost. The structural shell is 50%, the refrigeration plant is 25%, the cladding is 15%, and the electrical systems are 10%. All four qualify for separate depreciation under IAS 16.43.
Documentation note: record each component's cost as a percentage of total asset cost. Reference the project engineer's completion certificate and the entity's componentisation policy (threshold: 10% of total cost).
Step 2 — Calculate the annual depreciation charge
Structural shell: EUR 2,400,000 / 40 = EUR 60,000. Refrigeration plant: EUR 1,200,000 / 12 = EUR 100,000. Insulated panel cladding: EUR 720,000 / 20 = EUR 36,000. Electrical systems: EUR 480,000 / 10 = EUR 48,000. Total annual charge: EUR 244,000.
Documentation note: record the individual component charges. Note that a single blended life of 40 years over the full EUR 4.8M cost would produce a charge of only EUR 120,000 per year, understating depreciation by EUR 124,000 annually.
Step 3 — Compare to a non-componentised approach
If Rossi had depreciated the warehouse as a single asset over the 40-year structural life, the annual charge would be EUR 120,000 versus the componentised EUR 244,000. On a pre-tax basis, the difference of EUR 124,000 per year is material (approximately 1.8% of typical group pre-tax profit for a EUR 67M revenue food producer).
Documentation note: record the comparison to demonstrate that componentisation has a material effect on the financial statements. Cross-reference to the materiality assessment in the planning memorandum.
Step 4 — Plan for future component replacements
The refrigeration plant has a 12-year life. When Rossi replaces it (expected around 2037), IAS 16.70 requires derecognition of the old refrigeration component's remaining carrying amount at that date. The replacement cost is capitalised as a new component with a fresh useful life estimate.
Documentation note: flag the expected replacement cycle in the permanent file so that future engagement teams verify derecognition when a component replacement occurs.
Conclusion: the componentised depreciation charge of EUR 244,000 is defensible because each component's cost is significant relative to the total, each useful life ties to engineering evidence, and the difference from a blended approach is material.
Why it matters in practice
- The FRC's 2022/23 thematic review on PP&E found that several entities treated complex assets (buildings, production lines) as single depreciable units despite clear differences in the useful lives of their parts. Audit teams accepted the single-life treatment without testing whether componentisation would produce a materially different charge. IAS 16.43 does not give entities a choice to ignore components when parts have significantly different useful lives.
- Teams frequently identify the correct components at initial recognition but fail to derecognise the old component when a replacement occurs. IAS 16.70 requires the entity to derecognise the carrying amount of the replaced part. Without derecognition, the fixed-asset register carries both the old and new components, double-counting the depreciation charge and overstating the gross carrying amount.
Component depreciation vs. single-asset depreciation
| Dimension | Component depreciation (IAS 16.43) | Single-asset depreciation |
|---|---|---|
| Granularity | Each significant part depreciated separately over its own useful life | Entire asset depreciated over one blended useful life |
| Annual charge | Higher in most cases, because shorter-lived components accelerate the expense | Lower, because the longest-lived component dominates the blended rate |
| Register complexity | Requires tracking individual components with separate cost, life, and accumulated depreciation | One line item per asset |
| Replacement accounting | Old component derecognised under IAS 16.70; replacement capitalised as new component | Replacement cost often expensed or added to the asset without removing the old part |
| Audit focus | Whether the entity identified the right components and assigned supportable lives | Whether the single blended life is reasonable given the mix of component lives |
The distinction matters most for capital-intensive entities (manufacturing, infrastructure, real estate) where individual components like roofs, elevators, mechanical systems, and electrical installations have useful lives ranging from 10 to 50 years within a single building or facility.
Related terms
Frequently asked questions
How do I decide which parts of an asset to componentise?
Identify each part with a cost that is significant relative to the total cost of the item and a useful life that differs materially from the other parts. IAS 16.43 does not set a fixed percentage threshold, so document your firm's policy (commonly 10% to 20% of total asset cost) and apply it consistently. Group parts with the same useful life and method under IAS 16.45 to avoid unnecessary register complexity.
What happens when a component is replaced before the end of its useful life?
Derecognise the old component's remaining carrying amount under IAS 16.70 and recognise the replacement cost as a new component. If the old component was not tracked separately in the register, estimate its carrying amount at the date of replacement using the original cost allocation and accumulated depreciation. ISA 540.13(a) requires the auditor to evaluate whether the estimation method for that allocation is reasonable.
Does component depreciation apply to assets measured under the revaluation model?
Yes. IAS 16.43 applies regardless of whether the entity uses the cost model or the revaluation model. Under revaluation, each component is revalued and depreciated separately. The revaluation surplus or deficit is tracked per component, which adds register complexity but does not change the componentisation requirement.