The investor's cost base for capital gains tax purposes is reduced by the amount claimed. (en.wikipedia.org)
The market value of the mutual fund upon removing your mother's name would then become your new cost base for your own capital gains tax purposes. (moneysense.ca)
As well, portions of some distributions from income trusts such as REITs are treated as a return of capital for capital gains tax purposes. (tsinetwork.ca)