Abstract: An electronic cash register, wherein sales data such as sale information and classification information are input before a registration key is operated to cause a registration, includes a plurality of registration keys, a plurality of exemption flags each corresponding to the plurality of registration keys, an exemption flag set circuit for setting and resetting the plurality of exemption flags, an exemption flag detection circuit for detecting whether the set or reset condition of one of the plurality of exemption flags corresponding to one of the plurality of registration keys is actuated after the input of the sale data, and an exemption registration selection circuit responsive to the detection by the exemption flag detection circuit for selectively calculating the total sale price either free from the taxation or with the taxation.