A register system comprising: a handheld unit including a code scanner and a security tag signal reception unit; and a processor configured to determine whether or not a security tag on a product is deactivated based on whether or not the security tag signal reception unit receives a security tag signal from the product during scanning of a product code on the product, and register the product code for a transaction when the security tag is determined to be deactivated, wherein the handheld unit further includes a security tag deactivation unit that deactivates the security tag on the product when the code scanner is in a position to scan the product code on the product, wherein the register system further comprises: a display, wherein the processor is further configured to control the display to display a message that the security tag is being deactivated and to maintain the code scanner in the position to scan the product code on the product, when the security tag is determined to be not deactivated; and a fixed code scanner, wherein the processor is further configured to determine whether or not a product corresponding to a product code on the product and read by the fixed code scanner, is associated with a security tag, by referring to a product file using the product code read by the fixed code scanner, register the product code for a transaction, when the product is determined to be not associated with the security tag, and control the display to display an instruction to deactivate the associated security tag, without registering the product code, when the product is determined to be associated with the security tag. a handheld unit including a code scanner and a security tag signal reception unit; and a processor configured to determine whether or not a security tag on a product is deactivated based on whether or not the security tag signal reception unit receives a security tag signal from the product during scanning of a product code on the product, and register the product code for a transaction when the security tag is determined to be deactivated, wherein the handheld unit further includes a security tag deactivation unit that deactivates the security tag on the product when the code scanner is in a position to scan the product code on the product, wherein the register system further comprises: a display, wherein the processor is further configured to control the display to display a message that the security tag is being deactivated and to maintain the code scanner in the position to scan the product code on the product, when the security tag is determined to be not deactivated; and a fixed code scanner, wherein a display, wherein the processor is further configured to control the display to display a message that the security tag is being deactivated and to maintain the code scanner in the position to scan the product code on the product, when the security tag is determined to be not deactivated; and a fixed code scanner, wherein the processor is further configured to determine whether or not a product corresponding to a product code on the product and read by the fixed code scanner, is associated with a security tag, by referring to a product file using the product code read by the fixed code scanner, register the product code for a transaction, when the product is determined to be not associated with the security tag, and control the display to display an instruction to deactivate the associated security tag, without registering the product code, when the product is determined to be associated with the security tag. determine whether or not a product corresponding to a product code on the product and read by the fixed code scanner, is associated with a security tag, by referring to a product file using the product code read by the fixed code scanner, register the product code for a transaction, when the product is determined to be not associated with the security tag, and control the display to display an instruction to deactivate the associated security tag, without registering the product code, when the product is determined to be associated with the security tag.