SolvedETASSUM35250 | Schedule 3 SAYE option schemes: Requirements relating to share options – The exercise price: Bonus issues
From HM Revenue & Customs · Employee Tax Advantaged Share Scheme User Manual
Adjustments to options to reflect bonus issues are usually straightforward and may be dealt with without reference to HMRC Shares & Assets Valuation (SAV). For example, a 1:1 bonus issue will double the number of shares under option and halve the option acquisition price.