A charging data record (CDR) is, in telecom, a formatted collection of information about a chargeable telecommunication event. CDRs are used for user billing: a telecom provider transfers them from time to time in order to send bills to their users. CDRs are sent using the GTP' or FTP protocol.
Information on chargeable events includes time of call set-up, duration of the call, amount of data transferred, etc. A separate CDR is generated for each party to be charged.