b'94 Mercia Asset Management PLC Annual Report and Accounts 2021Notes to the consolidated financial statements continued6. Share-based paymentsThe Group operates share option schemes for Executive Directors and all employees of the Group. Further details are set out onpages 69 to 71 of the Remuneration Report.Total options existing over Ordinary shares as at 31 March 2021 are summarised below:scheme date of grant date of expiry number of share options exercise priceApproved share option scheme 28 August 2018 27 August 2028 734,043 30.80p31 July 2019 30 July 2029 1,882,892 33.50p28 January 2020 27 January 2030 1,651,111 24.30p21 August 2020 20 August 2030 1,306,761 21.50pUnapproved share option scheme 28 August 2018 27 August 2028 2,872,957 30.80p31 July 2019 30 July 2029 865,108 33.50p28 January 2020 27 January 2030 3,351,029 24.30p21 August 2020 20 August 2030 8,120,239 21.50p20,784,140Details of the share options outstanding as at 31 March are as follows:Year ended 31 March 2021 Year ended 31 March 2020number of Weighted share average exerciseNumber of shareWeighted average options price options exercise priceShare options outstanding as at 1 April 15,700,140 30.22p 13,413,000 41.99pGranted during the year 9,497,000 21.50p 9,040,140 27.99pForfeited during the year (1,830,000) 30.18p (1,108,000) 36.03pExpired during the year (2,583,000) 37.21p (5,645,000) 50.81pshare options outstanding as at 31 March 20,784,140 25.37p 15,700,140 30.22pThe options outstanding at 31 March 2021 had a weighted average remaining contractual life of two years (2020: two years). No share options were exercised during the years ended 31 March 2021 or 31 March 2020.Fair value chargeThe fair value charge for the share options in issue has been based on the Black-Scholes model with the following key assumptions:share priceexercise at date of risk-free assumed time assumed Fair valuedate of grant price grant rate to exercise volatility per option28 August 2018 30.80p 30.80p 1.0% 10 years 30% 12.22p31 July 2019 33.50p 33.50p 1.0% 10 years 30% 13.29p28 January 2020 24.30p 24.30p 1.0% 10 years 30% 9.64p21 August 2020 21.50p 21.50p 0.5% 10 years 40% 10.45pOn 21 August 2020, share options were granted with a total estimated fair value of 992,000. In the year ended 31 March 2020, share options were granted on 31 July 2019 and 28 January 2020 with an estimated aggregate fair value of 2,531,000.No dividends are included within the fair value assumptions made on the date of grant. The risk-free rate is taken from the yield on zero coupon United Kingdom Government bonds on a term consistent with the expected life. Assumed volatility is based on a review of comparators and analysis of movements in the Groups share price over the preceding three-year period to the date of grant.The Group did not enter into any share-based payment transactions with parties other than Executive Directors and employees during the year.The total charge for the year recognised in the consolidated statement of comprehensive income for share options granted to Executive Directors and employees was 543,000 (2020: 528,000).'