The relevant taxation law applying to investors is capital gains tax (CGT).
Capital gains tax concerns gains or losses made as a result of CGT assets.
In the current situation, the relevant CGT asset is considered to be a claim on the Common Fund that arose when the monies you paid to invest in one scheme were mixed with investment monies from other schemes.
When you receive your interim distribution out of the Common Fund, a CGT event occurs, and there may be capital gains tax consequences.
When you receive your final distribution out of the Common Fund, your claim is considered to have expired and CGT event C2 occurs.