Assume that the residual value in an open-end lease is $12,000, the realized value is $11,000, and the base monthly payment is $250. The end-of-term deficiency is $1,000. However, under the three-payment rule, the maximum charge should not exceed $750 (assuming that there are no excessive wear-and-tear or excessive mileage charges). You are not liable for the full $1,000 deficiency unless the lessor can prove that the residual value was reasonable when it was set.