Stocks are measured at the lower of cost and estimated selling price less costs to complete and sell. Cost is determined using the first in first out method. The carrying amount of stock sold is recognised as an expense in the period in which the related revenue is recognised. Short term debtors are measured at transaction price (which is usually the invoice price), less any impairment losses for bad and doubtful debts. Loans and other financial assets are initially recognised at transaction price including any transaction costs and subsequently measured at amortised cost determined using the effective interest method, less any impairment losses for bad and doubtful debts. Short term creditors are measured at transaction price (which is usually the invoice price). Loans and other financial liabilities are initially recognised at transaction price net of any transaction costs and subsequently measured at amortised cost determined using the effective interest method. A current tax liability is recognised for the tax payable on the taxable profit of the current and past periods. A current tax asset is recognised in respect of a tax loss that can be carried back to recover tax paid in a previous period. Deferred tax is recognised in respect of all timing differences between the recognition of income and expenses in the financial statements and their inclusion in tax assessments. Unrelieved tax losses and other deferred tax assets are recognised only to the extent that it is probable that they will be recovered against the reversal of deferred tax liabilities or other future taxable profits. Deferred tax is measured using the tax rates and laws that have been enacted or substantively enacted by the reporting date and that are expected to apply to the reversal of the timing difference, except for revalued land and investment property where the tax rate that applies to the sale of the asset is used. Current and deferred tax assets and liabilities are not discounted. A lease is classified as a finance lease if it transfers substantially all the risks and rewards incidental to ownership. All other leases are classified as operating leases. The rights of use and obligations under finance leases are initially recognised as assets and liabilities at amounts equal to the fair value of the leased assets or, if lower, the present value of the minimum lease payments. Minimum lease payments are apportioned between the finance charge and the reduction in the outstanding liability using the effective interest rate method. The finance charge is allocated to each period during the lease so as to produce a constant periodic rate of interest on the remaining balance of the liability. Leased assets are depreciated in accordance with the company's policy for tangible fixed assets. If there is no reasonable certainty that ownership will be obtained at the end of the lease term, the asset is depreciated over the lower of the lease term and its useful life. Operating lease payments are recognised as an expense on a straight line basis over the lease term. Contributions to defined contribution plans are expensed in the period to which they relate.