A sales data processing apparatus, comprising: a first antenna configured to receive, from a wireless tag attached to a commodity, tag information to uniquely identify the relevant commodity; a recovery box configured to recover the wireless tag detached from the commodity; a second antenna configured to receive the tag information from the wireless tag recovered by the recovery box, wherein the second antenna is provided inside the recovery box or in the vicinity of an inlet port of the recovery box; a processor which is configured to judge whether the first antenna has received the tag information, wherein, when judging, by the processor, that the tag information has been received by the first antenna, the processor is configured to judge, based on the received tag information, whether the wireless tag attached to the commodity is a wireless tag required to be detached from the commodity; and a notification device configured to perform notification that the wireless tag is required to be detached from the commodity; wherein, when judging, by the processor, that the wireless tag attached to the commodity is the wireless tag required to be detached from the commodity, the processor makes the notification device to perform a notification to instruct to detach the wireless tag from the commodity, wherein the processor is further configured to judge whether the second antenna has received the tag information of the wireless tag which is judged to be the wireless tag required to be detached from the commodity, and when judging, by the processor, that the tag information has been received by the second antenna, the processor makes the notification device to stop the notification and executes a sales registration processing of the relevant commodity, based on the relevant received tag information. a first antenna configured to receive, from a wireless tag attached to a commodity, tag information to uniquely identify the relevant commodity; a recovery box configured to recover the wireless tag detached from the commodity; a second antenna configured to receive the tag information from the wireless tag recovered by the recovery box, wherein the second antenna is provided inside the recovery box or in the vicinity of an inlet port of the recovery box; a processor which is configured to judge whether the first antenna has received the tag information, wherein, when judging, by the processor, that the tag information has been received by the first antenna, the processor is configured to judge, based on the received tag information, whether the wireless tag attached to the commodity is a wireless tag required to be detached from the commodity; and a notification device configured to perform notification that the wireless tag is required to be detached from the commodity; wherein, when judging, by the processor, that the wireless tag attached to the commodity is the wireless tag required to be detached from the commodity, the processor makes the notification device to perform a notification to instruct to detach the wireless tag from the commodity, wherein the processor is further configured to judge whether the second antenna has received the tag information of the wireless tag which is judged to be the wireless tag required to be detached from the commodity, and when judging, by the processor, that the tag information has been received by the second antenna, the processor makes the notification device to stop the notification and executes a sales registration processing of the relevant commodity, based on the relevant received tag information.