Cal. Code Regs. tit. 2, § 1071.8
Accounting for fixed assets sold or otherwise retired will depend upon the method of depreciation employed. For assets with individual cost and depreciation records, cost or recorded value is removed from the property accounts and the accumulated allowance for depreciation or amortization from the valuation reserve. Gain or loss, measured by the difference between:
Book value (Cost less accumulated depreciation)
and
Proceeds from sale or salvage
Removal or dismantling costs
Insurance proceeds
is posted to depreciation accounts as applicable.