Checkout system

A checkout system comprising an input unit and a settlement unit, wherein:

• the input unit comprises:
• a first memory storing executable instructions;
• and
• a first processor configured to execute the executable instructions stored in the first memory to perform operations including:
• receive an input of data on commodity sales or service rendering, and store transaction data for a settlement target in a the first memory based on the input data;
• receive an input of a charging amount for electronic money, and add amount data of the input charging amount to the first memory;
• and
• output the data stored in the first memory to the settlement unit;
• and
• the settlement unit comprises:
• a reader/writer configured to read and rewrite an electronic money balance stored in a storage medium;
• a second memory storing executable instructions;
• and
• a second processor configured to execute the executable instructions stored in the second memory to perform operations including:
• determine whether or not the data output by the input unit includes the amount data of the charging amount;
• determine, if the data output by the input unit includes the amount data of the charging amount, whether or not the electronic money balance read by the reader/writer is smaller than a transaction amount calculated based on the data output by the input unit;
• wait, if the electronic money balance is smaller than the transaction amount, for an amount of money equal to or greater than the charging amount to be received by a non-electronic money settlement method;
• and
• add, if the amount of money smaller than the charging amount is received by the non-electronic money settlement method, a shortage amount as a difference between the transaction amount and the electronic money balance to the electronic money balance via the reader/writer.