A sales data processing apparatus includes a display, a product scanner to obtain a commodity code from a product being registered in a sales transaction, a storage unit to store journal data including product information for registered. A controller is configured to record product information for products registered in the sales transaction and output a notification of an error in the sales transaction when detected. The notification is output to the display screen and includes information regarding resolution of the error. The controller executes a first countermeasure for resolving the error, then stops the sales transaction if the error is not resolved. The controller then executes a second countermeasure after the sales transaction has been stopped and starts a new transaction if the error is resolved by the second countermeasure.