Patent ID: 8489521

Claim:
An ink billing system that is used between a client that prints information and an ink supplier that supplies cartridges, which store ink, to the client, the ink billing system comprising: on the client side a first data processing apparatus; a plurality of second data processing apparatuses each in communication with the first data processing apparatus; and a plurality of printers each comprising a cartridge storing ink and a print head having nozzles for discharging the ink, each of the printers being in communication with, and receiving print data from at least one of the plurality of second data processing apparatuses, and wherein each of the plurality of printers discharges first ink from the nozzles onto paper based on the received print data for printing, discharges second ink from the nozzles for cleaning or recovering the nozzles, the second ink being consumed in the cleaning or recovering without being discharged onto the paper, and calculates an ink usage amount based on only the first ink by counting shots discharged from the nozzles, and wherein at least one of the second data processing apparatuses sends the ink usage amount received from one or more of the plurality of printers to the first data processing apparatus; and on the ink supplier side a terminal device in communication with the first data processing apparatus for receiving the ink usage amount from the first data processing apparatus, wherein the terminal device stores a billing rate table defining a unit cost of ink, the billing rate table enables changing the unit cost of ink based on an ink usage amount consumed in a predetermined period, and the terminal device calculates an invoice amount using the billing rate table and the ink usage amount received from the first data processing apparatus.