A Call Detail Record (CDR) (also Call Detail Recording) or Station Message Detail Recording (SMDR) in the telecom sector is a file containing information about recent system usage such as the identities of sources (points of origin), the identities of destinations (endpoints), the duration of each call, the amount billed for each call, the total usage time in the billing period, the total free time remaining in the billing period, and the running total charged during the billing period. The format of the CDR varies among telecom providers or programs. Some programs allow CDRs to be configured by the user.

A CDR for a particular account can be downloaded at the request of the subscriber who holds that account. If the telecom provider supplies users with itemized bills, a CDR will show up in each bill, in a format similar to that of an itemized long-distance telephone bill supplied by a conventional telephone company.

In a telephone exchange, a CDR contains information about all the calls passing through the exchange. The CDRs are generated by Automatic Message Accounting (AMA) and processed by the operations support system (OSS).

A CDR File may contain more than one type of call traffic. For example, fixed line voice traffic and fixed line data traffic may be placed in the same file, but will be identified separately for rating purposes.

Call accounting software or communication management software is generally used to retrieve and process CDR data.