Hello P L,
If you end up selling units which are not in an Isa and need to calculate CGT, it is not always as straightforward as it seems, especially if you have invested in instalments.
E.g. if you invested £10,000 and were lucky enough for it to grow to £20,000, you do not necessarily declare £10,000 profit.
You total up the number of units you have bought and the total cost and then divide one by the other to get the average price.
Then, you multiply the number of units sold by the average price which gives you the cost of the units sold.
The difference between the cost of the units sold and the value of the amount sold is the amount to be declared.
To put this into perspective, I recently took £2000 profit from a fund, but the amount of profit to be declared (using the above calculation) was only £835.
It could get quite complicated if there are incremental sales or profit taking, combined with many instalments and numerous re-invested dividends to calculate - having full records and being able to use a spreadsheet (or having an accountant or tax advisor!) obviously helps.
If you are nowhere near the CGT threshold it doesn't really matter, but if you think you are near it or over it, it obviously does.
I hope I have explained this correctly (and clearly).