PURPOSE: To provide a residual amount display system in the monthly discount service of a talking charge used efficiently by displaying the residual amount of the service charge for the monthly discount service on a user terminal equipment served with the monthly discount service.

CONSTITUTION: When a type of a monthly discount service, a dead line date, and its own telephone number are entered by a key entry section 9, the content is stored in a monthly discount service information recording section 10. A comparator section 7a compares an output from a clock circuit 5 and a calendar circuit 6 with information from the monthly discount service information recording section 10 representing a service period to output a signal representing whether or not the time is in the service period. When a call is made during the service period, an arithmetic operation section 7b receives called dial information and reads a station number of its own telephone number and reads a charge per call unit from a charge information storage section 11 based on the information and subtracts the used charge in response to the talking time from the residual amount and displays the result. The initial service charge is displayed at the start date of the service on next month.