Rating & Charging

Real-time vs batch rating, event types (recurring, usage, one-time), charge calculation, and the OCS architecture for prepaid.

What Rating and Charging Actually Do

Rating is the process of applying a monetary value to a usage event or subscription entitlement. Charging is the process of debiting or reserving that value against a customer's account. In postpaid billing, rating produces a charge that appears on the next invoice. In prepaid/real-time charging, the charge is applied immediately against a balance. The distinction matters because it determines latency, architecture, and failure modes.

Rating vs Charging

Rating calculates the price of an event based on the applicable tariff plan, discounts, and contract terms. Charging applies that calculated price to the customer's account — either as a deferred invoice line (postpaid) or an immediate balance deduction (prepaid/real-time). A single event is rated once but may be charged in different ways depending on the billing model.

Event Types and Charge Models

Telco billing must handle fundamentally different charge types. Each has different rating logic, timing, and data sources.

Charge Types

Charge Type	Trigger	Rating Input	Example
Recurring	Billing cycle (monthly, quarterly)	Subscription record from SLM, pricing from catalog	Monthly plan fee of $49.99
Usage-based	Each usage event (call, data session, SMS)	CDR/EDR from mediation, tariff plan from catalog	Voice call: 12 min at $0.05/min = $0.60
One-time	Activation, installation, or order event	Order completion event, fee from catalog	SIM activation fee of $25.00
Penalty / adjustment	Contract breach, manual correction	Contract terms, SLA breach data	Early termination fee of $200.00

Real-Time vs Batch Rating

The fundamental architectural split in billing is between batch rating (traditional postpaid) and real-time rating (prepaid and modern convergent systems). Most operators run both, creating integration complexity.

Batch rating — Usage records are collected over a billing period, rated in bulk at bill run time. Latency: hours to days. Simpler architecture but no in-session control. The customer sees charges only on the invoice.
Real-time rating (Online Charging System / OCS) — Each event is rated and charged immediately. Enables balance checks, spending limits, quota management, and in-session policy enforcement. Required for prepaid; increasingly used for postpaid to enable real-time spend visibility.
Near-real-time — A hybrid: events are rated within minutes (not at bill run) but without in-session blocking. Used for postpaid spend alerts and threshold notifications.

Rating Accuracy Depends on Catalog and SLM

The rating engine does not decide what to charge — it executes rules defined in the product catalog and applies them to the subscription context from SLM. If the catalog has incorrect pricing, or SLM shows the wrong plan, rating will produce wrong charges at scale. Most billing disputes trace back to catalog or SLM data issues, not rating engine bugs.

TM Forum Alignment

Rating and charging align with eTOM 1.1.1.8 (Manage Billing Events) and map to TMF Open APIs TMF678 (Customer Bill Management) for bill-level operations and TMF654 (Prepay Balance Management) for real-time balance operations. The 3GPP Online Charging System (OCS) specification (TS 32.296) defines the real-time charging architecture used in mobile networks.

Key Takeaways

Rating calculates the price; charging applies it to the account — the distinction determines architecture and latency
Four charge types: recurring, usage-based, one-time, and penalty/adjustment — each with different triggers and data sources
Batch rating suits traditional postpaid; real-time rating (OCS) is required for prepaid and increasingly used for convergent billing
Most billing errors originate in catalog pricing or SLM subscription data, not in the rating engine itself