PURPOSE: To provide an easy-to-handle commodity sale register data processor which can quickly and accurately perform the credit payment processing by means of a credit payment slip.

CONSTITUTION: This data processor is provided with a credit payment processing data storage table 14CDT, the payment processing data selection control means 12 and 13, the credit payment register processing execution control means 12 and 13, the credit payment processing execution control means 12 and 13, a credit payment executed data storage means 14CDM, and the credit payment executed data storage control means 12 and 13. Then the credit payment data are inputted by the data input means 15 and 16. Thus it is possible to perform the credit payment register processing and the credit payment processing while selecting automatically the credit payment processing data for each credit company and also to automatically store the credit payment executed data.