This document discusses retained earnings and how to calculate the cost of retained earnings. It defines retained earnings as the portion of net profits not paid out as dividends, but instead retained by the company to reinvest. The cost of retained earnings must be at least equal to the rate of return shareholders expect to receive from reinvesting dividends. The cost can differ from the cost of equity if shareholders face flotation costs or personal taxes on reinvested dividends. Two formulas are provided to calculate the cost of retained earnings depending on whether flotation costs and taxes apply. An example calculation is also shown.