What is ISP billing software?
ISP billing software runs the money side of an internet provider: it turns plans and subscriptions into invoices every cycle, adds the taxes and regulatory surcharges that apply, takes payments, and chases the ones that are late. What separates it from general accounting software is that it is tied to service. When a subscriber doesn’t pay, the system suspends their connection; when they do, it turns service back on.
In practice the category blurs into ISP management software, sometimes called OSS/BSS: the same platform that bills also holds the subscriber and contract record, provisions equipment on the network, tracks inventory and logs support tickets. Most operators should buy the broader platform, because every billing decision eventually has to change something on the network or in the support queue.
What should it handle?
At minimum, a system you can run a US ISP on should cover eight jobs:
- Recurring billing
- Plans, prorations, one-time charges, credits and cycle runs across thousands of accounts without manual edits.
- US taxes and surcharges
- Sales tax plus regulatory line items such as USF and E911 where your services require them.
- Dunning and automated suspend/reconnect
- Reminders, grace periods, suspension on your rules, and reconnection the moment a payment is confirmed.
- Payments
- ACH, cards, wallets and text-to-pay, reconciled against the invoice rather than matched by hand.
- Provisioning
- OLT/GPON for fiber, RADIUS and TR-069 for fixed wireless — so a billing event can change service state.
- Inventory
- Routers, ONUs and radios by warehouse, and which device is installed at which address.
- Ticketing
- Support cases logged against the subscriber, with assignment and SLA timers.
- Reporting
- Receivables, aging, collections and network indicators from the same data the invoices use.
The part most buyers underweight is the connection between them. Surcharges like USF and E911 have to land on the right invoices; dunning has to trigger a real suspension through RADIUS or the OLT; a cleared payment has to restore service without anyone opening a ticket. This is what that looks like when it works:
| ID | Event | Detail | Status | Value |
|---|---|---|---|---|
| #48201 | Auto-suspend | Past due · 4 days · policy DUNN-04 | Suspended | −1 service |
| #48202 | Auto-reconnect | ACH payment cleared · $74.00 | Reconnected | 2 min |
| #48203 | Cycle invoicing | Taxes, USF and E911 applied · emailed | Issued | 2,418 docs |
| #48204 | Payment reconciled | Paid via reminder link · matched to invoice | Cleared | +$74.00 |
When does a spreadsheet stack stop working?
Around 1,500 subscribers, a combination of spreadsheets, accounting software and manual process still works. It stops working somewhere between 3,000 and 10,000, when a missed invoice or a forgotten reconnection costs more than the software would.
The symptoms tend to show up before anyone decides to switch:
- Month-end means merging exports from billing, the network and the help desk.
- Suspensions and reconnections wait for someone to process them.
- Nobody can say, mid-call, what a subscriber owes and what equipment they have.
- Charges are missed or misapplied, and nobody finds out until a review.
Fiber vs fixed wireless requirements
Fiber operators need provisioning that talks to the OLT: registering each ONU to a port and applying a service profile on a GPON network, so that a new install or a plan change doesn’t need a network engineer.
Fixed wireless providers (WISPs) typically authorize sessions and speed profiles through RADIUS and manage customer equipment through TR-069. Suspension and reconnection usually run as a RADIUS change of authorization.
Many operators run both: wireless in the rural edge of the footprint and fiber in town. The subscriber record shouldn’t care which medium delivers the service, so pick a system that provisions both rather than one per network.
How to evaluate vendors
Feature lists in this category look alike. The differences show up in how the pieces connect and in what happens after the contract is signed. Use these questions as a scorecard:
| Ask | Why it matters |
|---|---|
Does billing, provisioning and support share one subscriber record? Separate systems mean exports, re-keying and numbers that disagree. | Separate systems mean exports, re-keying and numbers that disagree. |
Can suspension and reconnection run without a person? Manual reconnection is where weekend revenue and goodwill leak. | Manual reconnection is where weekend revenue and goodwill leak. |
Are USF, E911 and sales tax handled for the services you sell? Surcharge errors are invisible until an audit or a complaint. | Surcharge errors are invisible until an audit or a complaint. |
Does it provision your actual equipment? OLT/GPON, RADIUS and TR-069 support should be demonstrated, not listed. | OLT/GPON, RADIUS and TR-069 support should be demonstrated, not listed. |
Can you keep your payment processor? Forcing a processor switch adds risk to the migration. | Forcing a processor switch adds risk to the migration. |
What does migration include, and is there a parallel cycle? A parallel cycle is the only proof the new system bills correctly. | A parallel cycle is the only proof the new system bills correctly. |
Who answers when something breaks? Support should reach people who know your configuration. | Support should reach people who know your configuration. |
What migration should look like
Migration is where billing projects fail, so ask for the plan in writing. A sound one has three stages. First, subscribers, contracts, balances and equipment are moved across and every record is verified against your live base. Second, plans, billing cycles and dunning rules are configured and one full cycle runs in parallel with your current system. Third, you go live only when the parallel cycle matches.
With Inerxia that takes four weeks to the first full cycle: migration in weeks one and two, configuration and the parallel cycle in weeks two and three, go-live in week four. Migration, training and support are included rather than sold as add-ons.
Beyond the system of record: AI agents and call intelligence
A billing platform stores the truth about each subscriber. It does not answer the phone at 9 PM, negotiate a payment plan, or tell you what last month’s calls were actually about. That work still lands on your team, and it is where most of an ISP’s support cost sits.
This is the layer Inerxia adds on top of the record. AI voice and text agents authenticate subscribers, resolve routine cases and send reminders with your own payment links; the contact center puts calls, SMS and email in one queue; and Subscriber Intelligence transcribes every call, applies QA scoring to all of them and clusters issues by service location.
Zone 07 flagged. Ninety-four contacts from one service area in nine days, clustered before a single one was filed as an outage.
Questions to ask on a demo
Bring these to every vendor call, and ask to see each one rather than hear it:
- 1.Show me a subscriber who didn't pay being suspended, then reconnected when they did — with no one touching it.
- 2.Show me an invoice with sales tax and the regulatory surcharges that apply to my plans.
- 3.Provision an ONU or a RADIUS profile from the subscriber record.
- 4.What does my team see on screen when that subscriber calls?
- 5.Walk me through the migration plan and the parallel cycle, week by week.
- 6.What happens to my current payment processor?