1. Undiscounted Cash Flow Methods: In such methods future payments and receipts are not discounted. In other words: the discount rate is considered as zero. Because in most business world, interest is charged, these methods must be considered only as approximate and rough. However, because of their simplicity they are often used as a first screening of alternatives before applying the discounted cash flow methods. The most popular undiscounted cash-flow method is the Pay-back Period method. Pay-back Period Method. In this method, the time period during which the undiscounted future profits will just equal the original investment is calculated. That alternative is considered to be the best corresponding to which the payback period is the smallest.