Commissioner v. Idaho Power Co.
The Supreme Court held that depreciation on equipment a taxpayer uses to build its own capital assets must be capitalized into the cost of those assets. It is a basis case, not a MACRS classification case.
Educational information, not tax advice.
Updated 2026-10-14
Key takeaways
- Construction-related equipment depreciation is capitalized into the asset built, then recovered over that asset’s life.
- The decision is national precedent on capitalization and basis, not on MACRS class lives.
- §263A later expanded related capitalization rules; Idaho Power is not the complete modern statute.
- Educational information, not tax advice.
Case record
- Court
- U.S. Supreme Court
- Citation
- 418 U.S. 1 (1974)
- Decision date
- 1974-06-24
- Facts
- Idaho Power Company, a public utility, used its own transportation equipment — cars, trucks, power-operated equipment, and trailers — both to operate and maintain its system and to construct transmission lines, switching stations, distribution lines, and related capital facilities. On its regulatory books it charged construction-related depreciation to the assets being built, as the Federal Power Commission and the Idaho commission required. On its 1962 and 1963 federal returns it deducted all equipment depreciation currently under §167(a), including the construction-related portion. The Commissioner capitalized that portion under §263(a)(1), added it to the basis of the facilities, and allowed depreciation of the addition over the much longer lives of those facilities.
- Issue
- May a taxpayer currently deduct, under §167(a), depreciation on equipment used to construct its own capital facilities, or must the construction-related depreciation be capitalized under §263(a)(1)?
- Holding
- The construction-related portion must be capitalized. Accepted accounting and tax principles treat that depreciation as part of the cost of acquiring the capital asset constructed. Section 161 gives §263(a) priority over §167(a) on these facts. The Ninth Circuit was reversed.
- Reasoning
- Justice Blackmun wrote that depreciation accounting allocates the cost of using an asset over the periods benefited. Exhaustion of construction equipment is not the final disposition of that investment; the investment is assimilated into the cost of the facility built. Capitalizing that cost prevents current income from being offset by an acquisition cost, and it keeps a self-constructing taxpayer on a par with one that hires an independent contractor. “Amount paid out” in §263(a)(1) includes cost incurred, the same way wages and materials used in construction are capitalized. Where a regulator-required method clearly reflects income, it is almost presumptively controlling.
- Relevance to cost segregation
- The case explains why self-construction overhead, including equipment depreciation used in construction, belongs in depreciable basis before a study assigns recovery classes. It is not authority for treating a wall, panel, or land improvement as 5-year property. It predates the uniform capitalization rules of §263A.
Commissioner v. Idaho Power Co., 418 U.S. 1 (1974), is a Supreme Court capitalization case. The utility wanted a current §167(a) deduction for every dollar of transportation-equipment depreciation, including dollars that, on its own books, had already been charged to capital projects. The Commissioner allowed current depreciation only for equipment used in day-to-day operation and maintenance. The construction increment was added to the basis of lines and stations that would be depreciated over thirty years or more.
The Tax Court agreed with the Commissioner. The Ninth Circuit reversed, treating depreciation as a deduction Congress had enumerated and reading §263(a)(1)’s “amount paid out” as not covering a book depreciation entry. The Supreme Court reversed the Ninth Circuit. Construction-related depreciation, the Court said, is like construction wages: a cost of producing a capital asset. Deducting it currently would distort income by matching an acquisition cost against operating receipts.
Two institutional points in the opinion still matter for construction-cost studies. First, the Court gave weight to the fact that Idaho Power already capitalized the same depreciation for regulatory accounting, and that the method clearly reflected income. Second, §161’s ordering rule means a capitalization provision can take precedence over a depreciation deduction when both could be read to apply. The case is not about whether a constructed item is personal property or a structural component.
For cost segregation, Idaho Power is background on how costs enter basis. A new-construction study that ignores equipment, overhead, or interest that belongs in the building will understate the amount later split among classes. A study that invents a short recovery period for those capitalized costs still has to classify the resulting asset under §168 and Treas. Reg. §1.48-1. Super Intelligence, as proposed here, does not change that order of operations.
This page is educational information, not tax advice. The holding is national, but it answers a 1962–1963 utility question under §263(a), not a MACRS class-life question.
What was not decided
The Court did not classify building components. It did not assign recovery periods. It did not address whether a later cost segregation study may re-split a lump-sum contract. Those questions live in HCA, Scott Paper, and — for written purchase allocations — Peco Foods.
Justice Douglas dissented. The majority opinion is the national rule.
Later statutes
Section 263A later required capitalization of a broader set of direct and indirect costs of producing real property. Idaho Power remains good law on the narrower point that construction-equipment depreciation is a capital cost. Do not treat the 1974 opinion as a complete map of today’s uniform capitalization rules.
How a study should use the case
Start with the constructed asset’s total cost. Include the construction-related share of equipment depreciation, wages, and materials that the opinion treats as assimilated into that cost. Only then assign recovery classes under §168 and Treas. Reg. §1.48-1. Skipping the first step understates every class; inventing a short class for the capitalized increment still has to survive HCA and Whiteco.
A hired-contractor job presents the same idea in a different wrapper: the contractor’s equipment cost is already inside the contract price. Idaho Power’s point is that a self-constructing owner should not deduct that cost currently just because the equipment already sits on the owner’s depreciation schedule.
Educational information, not tax advice. The holding answers a 1962–1963 utility question, not a MACRS class-life question.
Verification. Verified from the Justia U.S. Reports text (argued February 27, 1974; decided June 24, 1974; Justice Douglas dissenting).
Sources
- 1
- 2IRS Publication 5653 — Cost Segregation Audit Techniques Guide (rev. 2-2025)(opens in a new tab)
Written for IRS examiners. The guide states it is not an official pronouncement of law and cannot be cited as authority. It predates the July 2025 law.