In the application of the company's accounting policies, the directors are required to make judgements, estimates and assumptions about the carrying amount of assets and liabilities that are not readily apparent from other sources. The estimates and associated assumptions are based on historical experience and other factors that are considered to be relevant. Actual results may differ from these estimates.
The estimates and underlying assumptions are reviewed on an ongoing basis. Revisions to accounting estimates are recognised in the period in which the estimate is revised where the revision affects only that period, or in the period of the revision and future periods where the revision affects both current and future periods.
Key sources of estimation uncertainty
The estimates and assumptions which have a significant risk of causing a material adjustment to the carrying amount of assets and liabilities are as follows.
Useful economic lives and residual values of tangible fixed assets
The annual depreciation charge for tangible fixed assets is sensitive to changes in the estimated useful economic lives and residual values of the assets. The useful economic lives and residual values are reviewed by the directors at each reporting date and revised where appropriate, having regard to the nature, condition, expected use and estimated disposal value of the assets.
During the year, the directors undertook a review of the residual values of certain tangible fixed assets and revised those estimates where the expected value of the assets at the end of their useful economic lives was considered to be material.
The revisions to residual values represent changes in accounting estimates and have therefore been applied prospectively. The effect of the revised estimates is reflected in the depreciation charge for the current year and, where applicable, future periods over the remaining useful economic lives of the relevant assets.
See note 4 for the carrying amount of tangible fixed assets and note 2.4 for the depreciation policies applied.