23 Leases Operating leases Leases where the lessor effectively retains substantially all the risks and benefits of ownership of the leased items are classified as operating leases. Operating lease expenses are recognised on a straight line basis over the period of the lease in the statement of financial performance. Cash and cash equivalents Cash and cash equivalents means cash balances on hand, cash held in bank accounts, term deposits with original maturities of three months or less and other highly liquid investments, in which the Commission invests as part of its day-to-day cash management. Debtors and other receivables Accounts receivable are stated at their estimated realisable value after providing for doubtful and uncollectable debts. When the receivable is uncollectible, it is written off against the provision for doubtful debts. Investments Investments in bank deposits are initially measured at fair value and subsequently at fair value less any provision for impairment. Impairment is established when there is objective evidence that the Law Commission will not be able to collect any amounts due according to the original terms of the deposit. Property, plant and equipment Property, plant and equipment asset classes consist of library collection, furniture and fittings, computer hardware and office equipment. All classes are initially recorded at cost. Library collections are stated at fair value. Fair value is determined using market based evidence by an independent valuer. Library collections are valued every three to four years. Additions between revaluations are recorded at cost. The carrying values of revalued items are reviewed at each balance date to ensure that those values are not materially different to f Accounting for revaluations The Commission accounts for revaluations of property, plant and equipment on a class of assets basis. The results of revaluing are credited or debited to an asset revaluation reserve for that class of asset. Where this results in a debit balance in the asset revaluation reserve, this balance is expensed in the statement