a housing for receiving a refrigerant tank;

a supply line for delivering refrigerant from the refrigerant tank to an identified refrigerant system;

a tank valve connected to said supply line and connectable to the refrigerant tank when the refrigerant tank is received in said housing for controlling delivery of the refrigerant;

said tank valve having an open position for delivering refrigerant from the refrigerant tank to the refrigerant system, and a closed position for blocking the flow of refrigerant from the refrigerant tank to the refrigerant system;

a sensor for determining the amount of refrigerant in the refrigerant tank when in said housing and generating an amount signal representing the amount of refrigerant in the tank at selected times;

a system controller operatively connected with said tank valve for generating control signals to control said tank valve;

a computer readable medium in communication with said system controller; and

a set of computer readable instructions in communication with said computer readable medium for operating said system during delivery of refrigerant to the refrigerant system including:

operating instructions for storing from said sensor an amount signal at a first selected time as an initial amount signal representing the amount of refrigerant initially in the tank, and transmitting an open signal to select said tank valve in said open position so that refrigerant is delivered to the refrigerant system;

said operating instructions transmitting a close valve signal to select said tank valve in said closed position so that the flow of refrigerant is blocked at a second selected time, and storing an amount signal from said sensor as a final amount signal representing the amount of refrigerant remaining in the tank at said second selected time;

a transaction file generated by said system controller containing amount data representing the amount of refrigerant delivered to the system indicated by the difference between said initial amount signal and said final amount signal, and said transaction file containing one or more of a location identity, a refrigerant system identity, a time and date of transaction, and a transaction ticket I.D.; and

storing instructions for storing said transaction file in said computer readable medium;

whereby a refrigerant supply history may be maintained in computer storage for verifying vendor invoices and performance of the identified refrigerating system.