If the investment is stock shares or mutual fund shares and the only thing that has happened since you invested is that the per - share price went up (there were no dividends paid or mutual fund distributions that occurred between the purchase and today) so your investment is now worth $ 12,000, then by all means you can withdraw $ 10,000 from your investment, but you can not withdraw only the original investment and leave the gains in the account; your
withdrawal will be partly the original post-tax money that you put in (and it will be not be taxed
upon withdrawal) and partly the gains on which you will
owe tax.