Future Values and Taxes Taxes can greatly affect the future value of your investment. The Financial Calculators Web site at www.fincalc.com has a financial calculator that adjusts your return for taxes. Suppose you have $50,000 to invest today. If you can earn a 12 percent return and no additional annual 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?