Plug and play driver for interfacing a cash register system with an automated payment system in combination with a cash register, characterized by comprising at least one unit configured for identifying, selecting and reading at least one data related to an overall amount to be paid calculated by the cash register; at least one unit configured for identifying, selecting and taking control of at least one control key of the cash register; at least one unit for identifying, selecting and acquiring a signal validating the payment of an amount generated by an automated payment system; at least one redirecting unit to redirect the signal for driving the control key to the automated payment system for controlling the said automated payment system and inhibiting the related command to the cash register; and which driver formats the data related to the overall amount into the expected format in the automated payment system and provides it to the same one and formats the signal for driving the control key into a command signal for driving the automated payment system, whereas it formats the signal validating the payment of the said overall amount generated by the automated payment system at the end of the transaction into a signal for commanding the cash register to carry out an expected function of the control key and provides the said signal directly, or upon user control, to said cash register for carrying out the said expected function, said driver being in the form of an application program loadable and executable by the cash register and/or by the automated payment system; and wherein said driver comprises a setup unit executing a program for selecting the data related to the said overall amount generated by the cash register system and of a display area of the said overall amount on a display and for selecting an input key of commands of the cash register to be used as the said control key of said automated payment system. at least one unit configured for identifying, selecting and reading at least one data related to an overall amount to be paid calculated by the cash register; at least one unit configured for identifying, selecting and taking control of at least one control key of the cash register; at least one unit for identifying, selecting and acquiring a signal validating the payment of an amount generated by an automated payment system; at least one redirecting unit to redirect the signal for driving the control key to the automated payment system for controlling the said automated payment system and inhibiting the related command to the cash register; and which driver formats the data related to the overall amount into the expected format in the automated payment system and provides it to the same one and formats the signal for driving the control key into a command signal for driving the automated payment system, whereas it formats the signal validating the payment of the said overall amount generated by the automated payment system at the end of the transaction into a signal for commanding the cash register to carry out an expected function of the control key and provides the said signal directly, or upon user control, to said cash register for carrying out the said expected function, said driver being in the form of an application program loadable and executable by the cash register and/or by the automated payment system; and wherein said driver comprises a setup unit executing a program for selecting the data related to the said overall amount generated by the cash register system and of a display area of the said overall amount on a display and for selecting an input key of commands of the cash register to be used as the said control key of said automated payment system.