Subscription Billing & SLM
Recurring charges, the SLM dependency, lifecycle events (activation, upgrade, suspension, cancellation), proration, and the bill run process.
Recurring Charges and the SLM Dependency
Most telco revenue is recurring: monthly plan fees, add-on subscriptions, equipment rental, and service charges that repeat every billing cycle. Recurring billing depends entirely on SLM (Subscription Lifecycle Management) as its source of truth. SLM tells billing what each customer has, when it was activated, what pricing applies, and what the current subscription state is (active, suspended, pending cancellation). If SLM is wrong, every recurring invoice is wrong.
Lifecycle Events That Affect Billing
Subscription billing is not simply "charge the monthly fee." Every subscription lifecycle event has billing implications that must be handled correctly. Getting these wrong is the leading cause of customer billing disputes.
Lifecycle Events and Billing Impact
| Event | SLM State Change | Billing Impact | Common Error |
|---|---|---|---|
| Activation | New subscription created, status = active | First recurring charge generated; proration from activation date to next bill date | Billing starts before service is actually active — customer charged for days without service |
| Upgrade / Downgrade | Plan changed mid-cycle, effective date recorded | Proration: credit for remaining days on old plan, charge for remaining days on new plan | No proration — customer charged full month on both old and new plan |
| Suspension | Status = suspended, suspension date recorded | Recurring charges paused or reduced (depends on suspension type — voluntary vs involuntary) | Charges continue during suspension; customer disputes on reactivation |
| Cancellation | Status = pending termination, end date set | Final prorated charge to termination date; early termination fee if applicable | Charges continue after cancellation date; refund processing required |
| Add-on change | Component added/removed from subscription | Prorated charge or credit for the add-on from effective date | Add-on charge starts but SLM not updated — billing and subscription out of sync |
The Bill Run Process
A bill run is the periodic process that generates invoices for a billing cycle. For large operators, bill runs process millions of accounts and must complete within a defined window (typically overnight). The bill run queries SLM for active subscriptions, applies rating rules, aggregates usage charges from mediation, calculates taxes and discounts, and produces invoice records.
- Bill cycle assignment — Accounts are assigned to bill cycles (e.g., 1st of month, 15th of month) to spread processing load. Enterprise accounts may have custom bill dates aligned to contract terms.
- Charge aggregation — Recurring charges (from SLM) and usage charges (from mediation/rating) are combined for each account. Discounts, promotions, and loyalty credits are applied.
- Tax calculation — Taxes are calculated based on service type, customer location, and applicable tax jurisdiction. In multi-country operations, tax rules vary significantly.
- Invoice generation — The final invoice is rendered (PDF, electronic, or both) and delivered to the customer via their preferred channel.
Key Takeaways
- Recurring billing depends on SLM as its single source of truth for what each customer has and what to charge
- Every lifecycle event (activation, upgrade, suspension, cancellation) has specific billing implications — proration, credits, and fees
- SLM-billing synchronisation is non-negotiable: divergence produces systematic billing errors at scale
- Bill runs must process millions of accounts within defined windows, combining recurring charges with usage from mediation