CDR reconciliation means comparing your own call (or message) records with the carrier's invoice, destination by destination and day by day. Small differences are normal and absorbed by a tolerance threshold in the agreement; larger ones are raised as a billing dispute with CDR evidence, within the deadline the agreement sets.
Why the two sides never match exactly
Both switches record every call, but they rarely produce identical totals. The usual reasons:
- Time zones and cut-off: one side closes the billing period at midnight UTC, the other at midnight local time.
- Rounding: different billing increments or rounding of rates to a different number of decimals.
- Duration measurement: small differences in when the answer and hang-up are timestamped.
- Rate deck timing: a new rate applied from a different date or hour (see rate changes and notice periods).
- Code mapping: a number billed under a different prefix or breakout, for example mobile instead of fixed.
These explain small differences. Large gaps usually come from traffic one side did not see, wrong rates, or fraud.
How to reconcile, step by step
- Align the period and time zone with the carrier before comparing anything.
- Summarise both sets of records by destination (or code group) and day: number of calls, billed minutes, amount.
- Compare the summaries. Mark lines where minutes or amounts differ beyond your tolerance.
- For those lines, match individual CDRs by called number, start time (within a few seconds) and duration.
- Classify each difference: missing on one side, different duration, different rate, different code.
- Check the rate applied against the deck valid at that moment.
For SMS the same method applies, matching on message ID, destination number and submit time, and comparing billed segments.
Tolerance thresholds and deadlines
Most agreements set a tolerance: if the difference is below a stated percentage of the invoice (often in the range of 1 to 2%) or below a fixed amount, no dispute is raised and the invoice is paid as issued. They also set a deadline to dispute, measured from the invoice date. A dispute raised after the deadline is usually rejected, so reconcile every invoice as soon as it arrives. Check your own agreement; the interconnect agreement checklist lists the clauses to look for.
Raising a dispute that gets resolved
| Include | Why |
|---|---|
| Invoice number and period | Identifies exactly what is disputed |
| Summary by destination and day | Shows where the gap is |
| Disputed amount and your calculation | Makes the claim concrete |
| Sample CDRs from both sides | Lets the carrier verify quickly |
| The reason, classified | Rate, duration, missing records or fraud |
Pay the undisputed part on time if the agreement allows it. Withholding the whole invoice over a small disputed line often leads to traffic being blocked and makes the discussion harder.
Quality and fraud disputes
Some disputes are not about arithmetic. Calls that were billed as answered but never reached a person point to false answer supervision. A sudden rise of traffic to unusual premium destinations may be IRSF. On SMS, messages charged but never received can indicate fake DLRs. These need evidence beyond CDR totals: test call recordings, handset checks, and timelines. Report them to the carrier quickly, since many agreements require prompt notice.
Prevent disputes before they start
- Agree the time zone, CDR source and rounding in writing.
- Load every rate deck on the stated effective date and keep the history.
- Monitor daily, not monthly: see monitoring route quality with CDRs.
- Set alerts for spikes in traffic, short calls or new destinations.
Routes bought through VoIPMatcher are sourced from our carriers and managed by us, so billing questions on those routes come to us. Read about our VoIP termination routes, or request a VoIP route.
Frequently asked questions
What is a CDR in telecom?
A CDR (call detail record) is the record a switch writes for every call: calling and called number, start time, answer time, duration, route and the rate or cost applied. For SMS the equivalent record holds the message ID, destination, submit time and segments. CDRs are the evidence used for billing, reconciliation and quality analysis.
How long do I have to dispute a carrier invoice?
The deadline is set in your interconnect agreement and runs from the invoice date. It varies between agreements, so read the clause before you need it. A dispute raised after the deadline is usually rejected, which is why carriers reconcile each invoice as soon as it arrives instead of at the end of the month.
Should I withhold payment during a billing dispute?
Pay the undisputed part on time if the agreement allows it, and withhold only the disputed amount, with your evidence. Holding back a whole invoice over a small line often gets traffic blocked and makes the dispute harder to settle. Check the agreement first, because some contracts set their own rules for payment during a dispute.
Whose CDRs are used for the invoice?
The agreement should say whose CDRs are the source of truth, and your own records are then used to check the invoice. Agree in writing the CDR source, the time zone of the billing period and the rounding rules, because most small differences between two sets of records come from these three points.
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