Assuming your funds are outside a pension or an ISA , then you will need to go back through all of your records . Unit trusts are taxed for CGT in the same way as ordinary shares under s . 99 of Taxation of Chargeable Gains Act 1992 . If you actually have an OEIC , they are also taxed in the same way as unit trusts under The Authorised Investment Funds Tax Regulations 2006 . The main effect of this is to ensure that your holdings in the same fundsubfund are subject to the share pooling rules , i . e . a section 104 of TCGA 1992 holding . andcapitalgainstaxhs 284 s e l f a s s e s s m e n t h e l p s h e e t h ssharesandcapitalgainstax 2015 Every time an Accumulation fund has a distribution , it is chargeable to income tax as a notional dividend , even though you receive no money . On the flip side , as those distributions are used to purchase new units of the fund , then you need to update the value of the pool at that point . You need to go back to every distribution date and work out the new value of the pool at each time . When you convert from Accumulation to Income units , s . 127 of the Act Applies it ' s a reorganisation No CGT charge is triggered nor update of the original acquisition date . From old HMRC guidance back in 1998 On a separate point , we have been asked to explain the CGT treatment where an investor switches between income units and accumulation units in the same subfund of an authorised unit trust umbrella scheme . Section 102 TCGA 1992 does not apply in these circumstances . This is because both the old units and the new units treated as shares by Section 99 TCGA 1992 provide rights to participate in the same separately pooled part of the scheme property . So , where an investor switches between income units and accumulation units in a single subfund of an umbrella scheme , Section 127 TCGA 1992 can apply . In a straightforward switch , where no consideration is given or received apart from the old units and the new units , the switch would be treated as not giving rise to any disposal for CGT purposes . The new units will be treated as having the same date of acquisition , and the same capital gains cost , as the old units . you must be sure of the acquisition cost at the date of switching , which means taking into account of all the previous distributions or you will overpay CGT .