Do i get taxed on investments growth that i haven't touched? For example growth in a mutual funds investment account

[SusanY1]

While you're not taxed on the change in value until you sell mutual funds often have dividends and something called "capital gain distributions" which represent your share of capital gains from transactions inside of the fund.  Those items are taxable to you in the year that they are reported, even if you leave them in the fund or reinvest them. 

They do, however, also increase the "basis" in those funds which will lower any gain when you do later redeem the funds.