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Section 6.8

Interconnect & Roaming Billing

Last updated 12 Oct 2026

At a glance

When traffic crosses from one operator’s network to another’s, the operators owe each other money. Interconnect billing settles calls, SMS and data exchanged between networks; roaming billing charges your subscriber for usage abroad and settles with the visited operator. Both rest on reconciling records that two companies produced separately.

The picture

One roaming data session, four records of it. Wholesale reconciliation alone says everything is fine.

1 · Usage abroad

Data session

Home subscriber on a visited network

2 GB used

TAP arrives in days; NRTRDE in hours

2 · Four records

Partner records2 GB
Visited operator, via TAP
Network records2 GB
Home mediation (and NRTRDE)
Wholesale charges2 GB, paid in full
Home wholesale billing
Customer charges0.5 GB
Home retail rating and billing

Roaming add-on applied to the wrong zone

3 · Pairwise checks

Partner ↔ NetworkAgree
Partner ↔ WholesaleAgree
Customer ↔ Partner1.5 GB not billed

Settlement checks only the first two

4 · Finding

Retail leakage

Invisible to the partner and to wholesale settlement

Owner: Revenue Assurance / wholesale operations

One roaming data session leaves four records. Partner, network and wholesale agree; the customer was charged for a quarter of it, and only customer-versus-partner comparison finds that (example figures)

How it works

Interconnect settlement

When your subscriber calls a number on another operator’s network, your network originates the call and the other operator terminates it. The originating operator owes the terminating operator a per-minute or per-event interconnect rate. Interconnect billing processes the inter-operator records, applies the agreed rates, produces settlement statements and reconciles discrepancies. Settlement is typically monthly, under bilateral agreements or regulatory rate cards.

Roaming: three flows and the GSMA standards

Roaming usage triggers three flows. The visited network records the usage and sends it home. The home operator rates it and charges its subscriber. The home operator then settles wholesale charges with the visited operator. The exchange formats are GSMA standards.

Standard	Purpose	Direction	Main difficulty
TAP (TAP3)	Roaming usage records	Visited → home	Arrives days after usage, so the customer bill can lag a cycle
RAP	Returns rejected TAP records with error codes	Home → visited	Rejected records must be corrected and resubmitted, or written off
NRTRDE	Near-real-time summaries of high usage, within 4 hours	Visited → home	Exists mainly to shorten the fraud window TAP latency opens
Financial clearing	Settlement between roaming partners	Bilateral or via a clearing house	TAP volumes, exchange rates and inter-operator tariff discrepancies

Roaming settlement in sequence

Usage abroad

Visited network / home OCS

The visited network records it. For real-time charged subscribers the home OCS authorises it during the session.

TAP and NRTRDE

Visited operator → clearing house → home

TAP records arrive within days; NRTRDE sends a summary within hours, mainly for fraud and high-usage control.

Validation and RAP

Home wholesale billing

Records the home operator cannot accept (unknown subscriber, late, wrong format) go back in a RAP file.

Retail charging

Home retail rating / billing

Accepted records are rated against the roaming tariff, unless already charged in real time, and reach the invoice.

Wholesale settlement

Wholesale billing / clearing

Both sides calculate what is owed under the inter-operator tariff and any discount agreement; the clearing house nets positions.

Reconciliation

Revenue Assurance / wholesale operations

The four records are compared. Gaps become disputes, write-offs or retail corrections.

Bilateral, clearing house or hub

Bilateral: two operators exchange statements monthly, reconcile and settle the net. Workable for a few partners; it does not scale.
Clearing house: a third party collects TAP files from all partners, reconciles, calculates net positions and manages financial clearing. Most operators with significant roaming use this model.
Hubbing: the hub also handles steering, fraud detection and NRTRDE processing alongside settlement.

Four views of the same traffic

Retail billing reconciles two things: what the customer used and what they were charged. Wholesale adds a partner, so four records must agree, and one of them belongs to a different company.

View	Produced by	Question it answers
Customer charges	Home retail rating and billing	What did we charge our subscriber?
Network records	Home mediation (and NRTRDE feed)	What does our own network say happened?
Partner records	Visited operator, via TAP and settlement statements	What does the partner say our subscriber used?
Wholesale charges	Home wholesale billing, under the agreement	What do we owe the partner, or they us?

Each pair answers a different question. Settlement compares partner records with wholesale charges, so a retail error, such as a roaming add-on applied to the wrong zone, passes settlement cleanly. Only customer charges against partner or network records finds it.

Wholesale billing is its own system

Wholesale billing (interconnect, roaming, MVNO hosting, transit, wholesale access) has partners instead of customers, agreements instead of product offerings, and settlement statements instead of invoices. Its volumes, rate structures (per route, per destination, tiered, commitment-based) and disputes differ, so it often runs on a separate platform. That fits wholesale better but needs its own reconciliation to retail. The partner relationship is modelled with TMF651 Agreement Management; TMF654 Prepay Balance Management applies to real-time roaming spend control.

Who owns what

Entity	System of Record	System of Engagement	System of Reference	Notes
Interconnect or roaming agreement (rates, discounts)	Wholesale billing / partner agreement management	—	Revenue Assurance	TMF651. The rate actually applied must match the rate agreed.
Partner usage records (TAP)	Visited operator	Clearing house	Home wholesale billing	The home operator holds a copy; it does not own the truth of what the partner recorded.
Own network usage records	Home mediation	—	Revenue Assurance, fraud management	—
Settlement statement and net position	Wholesale billing (or the clearing house, where used)	—	Finance / ERP	—
Roaming charges on the customer bill	Retail billing	OCS (for real-time charged usage)	—	The only one of the four views the partner never sees.

In practice

Legacy reality

Interconnect and roaming are high-leakage domains. Records are dropped between mediation and wholesale billing, applied rates drift from agreed rates, TAP deliveries fail and RAP processing runs late. Unlike retail, nobody complains: each party assumes its own records are right, so wholesale leakage often goes undetected.

Most operators with meaningful roaming volume outsource clearing to a clearing house or hub (for example BICS or Syniverse) and keep bilateral settlement for a small number of interconnect partners. The wholesale platform is frequently a separate product from retail billing and is often the billing system that receives the least investment. Its reconciliation to retail is the gap the four-way comparison exists to close.

TAP latency means a roaming session can reach the customer bill a cycle late, after the customer has already disputed or churned. Real-time charging through the OCS removes the retail lag for those subscribers, but not the wholesale settlement lag.

The trade-off

What it solves

Standard exchange formats and clearing let thousands of partner relationships settle on agreed terms without each pair building its own process.

What it does not solve

Retail errors on roaming charges, which settlement never sees.
TAP latency, which delays both the customer bill and fraud detection.
Rate drift between what was agreed and what wholesale billing applies.

What it adds

A separate wholesale platform that must reconcile to retail and to finance.
Disputes, RAP returns and write-offs that need owners and deadlines.
Four records of the same traffic, one of them held by another company.

Architecture decision

Settle roaming bilaterally or through a clearing house?

Bilateral
Choose when there are few partners, volumes are low, and the team can reconcile each statement itself.
Clearing house
Choose when roaming covers many partners and net settlement across all of them outweighs the fees and the dependency.
Hub with fraud and NRTRDE
Choose when fraud exposure from TAP latency is material and you want one party running steering, NRTRDE and settlement.

Breaks if the clearing house is treated as the reconciliation. It checks partner against partner; nobody checks customer charges against partner records, and retail leakage runs for years.

Takeaways

Key Takeaways

Interconnect billing settles traffic between operators at agreed rates, usually monthly
Roaming uses GSMA standards: TAP for usage, RAP for rejects, NRTRDE for near-real-time high-usage alerts
Most operators with significant roaming settle through a clearing house rather than bilaterally
Wholesale adds a partner: customer charges, network records, partner records and wholesale charges must all agree
Wholesale leakage goes unnoticed because each party trusts its own records; reconciliation is the control

Check yourself

Settlement with a roaming partner reconciles perfectly every month. Can you conclude roaming revenue is complete?Show answerHide
No. Settlement compares partner records with wholesale charges. A retail rating error, such as an add-on applied to the wrong zone, under-charges the customer and still settles cleanly. You need to compare customer charges with partner or network records.
Why does NRTRDE exist when TAP already carries every roaming record?Show answerHide
TAP arrives days after usage. NRTRDE sends a summary within about four hours, so the home operator can see high usage and fraud while it is happening and apply spend limits.
A partner’s TAP records are rejected for unknown subscribers. What happens to them?Show answerHide
The home operator returns them in a RAP file with error codes. The visited operator corrects and resubmits them, or writes them off. Unresolved RAP is a dispute that needs an owner.