The Company issues equity-settled share options to certain employees. Equity-settled share-based payment transactions are measured at fair value (excluding the effect of non market-based vesting conditions) at the date of grant. The fair value determined at the grant date of the equity-settled share-based payments is expensed on a straight-line basis over the vesting period, based on the Company's estimate of shares that will eventually vest and adjusted for the effect of non market-based vesting conditions.
Fair value is measured by use of the Black Scholes pricing model which is considered by management to be the most appropriate method of valuation. The expected life used in the model has been adjusted, based on management's best estimate, for the effects of non-transferability, exercise restrictions, and behavioural considerations.
The fair value of options offered under equity settled share based payment schemes is determined at grant date and expensed in the profit and loss account over the vesting period with a corresponding credit to retained earnings.
Where vesting conditions apply, the expense is allocated over the vesting period, based on the best available estimate of the number of share options expected to vest. Non-market vesting conditions are included in assumptions about the number of options that are expected to become exercisable.
Estimates are subsequently revised if there is any indication that the number of share options expected to vest differs from previous estimates. Any adjustment to cumulative share-based compensation resulting from a revision is recognised in the current period.
The number of vested options ultimately exercised by holders does not impact the expense recorded in any period.
Upon exercise of share options, the proceeds received, net of any directly attributable transaction costs, are allocated to share capital up to the nominal value of the shares issued with any difference allocated to the share premium account.