Investments Unlisted investments are measured at fair value unless the value cannot be measured reliably, in which case they are measured at cost less any accumulated impairment losses. Any changes in fair value are included in the profit and loss account on an annual basis. Debtors Short term debtors are measured at transaction price (which is usually the invoice price), less any impairment losses for bad and doubtful debts. Creditors 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. Taxation 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. Pensions Contributions to defined contribution plans are expensed in the period to which they relate.