Question: Future Values and Taxes. Taxes can greatly affect the future value of your investment. The website at www.fincalc.com has a financial calculator that adjusts your return for taxes. Go to this web page and find this calculator. Suppose you have $50,000 to invest today. If you can earn a 12 percent return, and you have no additional savings, how much will you have in 20 years? (Enter 0 percent as the tax rate.) Now, assume that your marginal tax rate is 27.5 percent. How much will you have at this tax rate?