IFM03370 - Authorised investment funds (AIFs): taxation of investors within the charge to IT: disposals
A disposal of units in an authorised investment fund (including shares in an open-ended investment company) may give rise to a charge to capital gains tax.
For more details please see the capital gains manual from CG57680.
Umbrella schemes / umbrella companies
Please see IFM02140 for an explanation of these and the tax treatment applying.