Cal. Code Regs. tit. 18 § 24349(d)
Capital expenditures made by a lessee for the erection of buildings or the construction of other permanent improvements on leased property are recoverable through allowances for depreciation or amortization. If the useful life of such improvements in the hands of the taxpayer is equal to or shorter than the remaining period of the lease, the allowances shall take the form of depreciation under Section 24349. If, on the other hand, the estimated useful life of such property in the hands of the taxpayer, determined without regard to the terms of the lease, would be longer than the remaining period of such lease, the allowances shall take the form of annual deductions from gross income in an amount equal to the unrecovered cost of such capital expenditures divided by the number of years remaining of the term of the lease. Such deductions shall be in lieu of allowances for depreciation. See Section 24343 and the regulations thereunder. Capital expenditures made by a lessor for the erection of buildings or other improvements shall, if subject to depreciation allowances, be recovered by him over the estimated life of the improvements without regard to the period of the lease.
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*** This regulation is substantially the same as Section 26 CFR 1.167(a)(4).
Cal. Code Regs. Tit. 18, § 24349(d)