A capital gain is the difference between what you sold units for and what you paid. On equity funds, gains on units held over twelve months are long-term capital gains, taxed at a flat rate above an annual exemption. Gains on units held under twelve months are short-term, taxed at a higher flat rate.
Because of the annual exemption on long-term equity gains, redeeming a little every year can be cheaper than redeeming a lot at once. This is called harvesting, and it is legal and routine.
Losses can be set off against gains, short-term against either kind and long-term only against long-term, and unused losses can be carried forward for eight years if you file your return on time. Keep your statements; the RTA and Crowwd both provide a capital gains report at year end.
Hold past twelve months, redeem in slices, and file your losses. Tax is a design problem.