A call detail record (CDR) is the record a phone system, VoIP platform or carrier creates for each call, capturing details such as the calling and called numbers, start time, duration, how the call was routed and whether it was answered. CDRs describe calls without capturing what was said. Carriers use them for billing, and businesses use them to check invoices, report on call activity, spot fraud and settle disputes.
At a glance
- A CDR is metadata about a call, not a recording of it.
- Typical fields include calling number, called number, start and end time, duration, call direction, trunk or route used, result (answered, busy, failed) and, for carriers, rating and charges.
- Phone systems, UCaaS and contact center platforms, SIP trunking providers and carriers all generate CDRs, each with their own fields and formats.
- Businesses use CDRs for cost allocation, invoice audits, usage reporting, fraud detection and dispute resolution.
- CDRs can include personal data, so access, retention and privacy rules apply.
What problem it solves
Usage-based phone bills and call reports depend on knowing what calls happened. Without call-level records, a business cannot check whether a carrier billed correctly, which locations or departments are driving cost, whether a spike in international calls is fraud, or whether a customer’s call actually reached the contact center.
CDRs provide that evidence. They let finance and telecom teams reconcile invoices, let IT spot unusual activity, and let managers see call volumes, missed calls and busy periods. In a billing dispute, CDRs from both sides are often the deciding record.
How it works
Creation. When a call starts, the phone system, switch or VoIP platform begins a record and completes it when the call ends. In VoIP systems, the details come largely from SIP signaling: who called, what number was dialed, when the call was answered and why it ended. The calling number, such as the ANI, is a core field.
Collection and formatting. Carriers pass raw records through mediation systems that clean and standardize them. Business phone platforms store them in a database behind their admin portal.
Use. Records are rated against price plans for billing, loaded into reporting tools, and exported to analytics, telecom expense management (TEM) or security systems. Routing engines, including least-cost routing, use CDRs to see which route each call took and what it cost.
Retention. Records are kept for a set period, which depends on the provider’s practices, your contract and any legal requirements that apply.
When it matters for buyers
- When auditing telecom spend. CDRs are the detail behind invoice charges and the starting point for a telecom audit. Our telecom expense management overview covers services that use them.
- When choosing a UCaaS, hosted PBX or SIP trunking provider. Reporting depth, export options and retention vary widely. See our SIP trunking overview.
- When protecting against toll fraud. Monitoring CDRs for unusual destinations and volumes can catch fraud early.
- When switching providers. Export historical CDRs before the old account closes.
- When privacy rules apply. CDRs show who contacted whom and when, which can be personal data. Using them to monitor employees may raise privacy or labor questions depending on where you operate.
Questions to ask vendors
- Which fields are included in your CDRs, and do they include the trunk, route, cost and call result?
- How far back can we view and export CDRs, and in which formats (CSV, API, scheduled reports)?
- Can CDRs be sent automatically to our TEM, analytics or security tools?
- How quickly do CDRs appear after a call ends?
- Do you offer alerts for unusual calling patterns or possible toll fraud?
- How are CDRs protected, who at your company can access them, and where are they stored?
- What happens to our CDR history if we leave?
How it differs from call recording
A CDR documents that a call happened and describes it: numbers, times, duration, route and result. Call recording captures the audio of the conversation itself. Phone systems typically create CDRs for calls by default, while recording is a feature that must be turned on and, depending on where the parties are, may require notice or consent. Recordings take far more storage and raise more privacy concerns. A related term, the IP detail record (IPDR), applies the same idea to data sessions rather than calls. CDRs also differ from the call log on a phone, which shows only that user’s own calls; CDRs are system- or carrier-level records covering the whole organization, whether it runs on a VoIP platform or traditional lines.
Problems this helps with
- Can't tell why our phone bill went up
- Need to prove a call happened, or didn't, in a billing dispute
- Want reports on call volume and missed calls across locations
- Worried about toll fraud or unexpected international calls
