Absolute entitlement: special cases: class closing rules: introduction
You should check the other guidance available on GOV.UK from HMRC as Brexit updates to those pages are being prioritised before manuals.
In practice, because deeds are no longer examined, you are unlikely to have any reason to doubt that the trustees are correct when they apply the class closing rules and indicate that absolute entitlement has therefore occurred. However cases may arise where the trustees claim that because of the class closing rules absolute entitlement occurred many years ago. You should examine such cases critically.