How to Automate ISP Billing: A Complete Guide
Manual billing does not fail loudly. It fails as a slow leak: an invoice that was never issued, a subscriber who cancelled six months ago and is still using the service, a failed direct debit nobody chased, a customer disconnected the day after they paid. This guide describes the full automated chain — from service activation to collection and reconnection — and, more usefully, the parts that go wrong and how to make them safe.
The Chain You Are Actually Automating
ISP billing is not one task. It is a sequence where each step depends on the previous one being correct:
- Service and plan definition — price, VAT rate, bandwidth, contract term, activation fee, whether it is prepaid or postpaid.
- Activation and proration — a subscriber connected on the 18th should not be charged a full month, and the rule you pick has to be applied identically every time.
- Invoice generation — one run per cycle, on a fixed day, producing a legally numbered document per subscriber.
- Delivery — email or portal, plus e-invoicing submission where the tax authority requires it.
- Collection — direct debit, card, bank transfer, cash at a point of sale.
- Reconciliation — matching money received to invoices issued, which is where most of the manual hours actually go.
- Dunning — reminders on a schedule, with escalating wording.
- Enforcement — restriction or suspension of the service.
- Reconnection — automatic, within seconds of payment.
Automating steps 3 and 4 while leaving 6 and 9 manual is the most common half-finished state, and it saves almost nothing: reconciliation and reconnection are the steps that consume staff time and generate angry calls.
Invoice Generation: Rules to Decide Once
Before automation, write down the answers. Ambiguity here becomes a support ticket every month.
- Billing day. A single fixed day for everyone is far simpler to operate than each subscriber's own anniversary, and it makes your cash flow predictable.
- In advance or in arrears. Most ISPs bill the coming month in advance. This matters for what happens on cancellation.
- Proration rule. Daily proration, half-month, or none. Pick one and apply it to activations, upgrades, downgrades and cancellations alike.
- Invoice numbering. An unbroken sequence per series, never reused, never reordered. Cancellation is a credit note, never a deletion.
- VAT and rounding. Decide whether prices are stored net or gross and round per line or per invoice. This single decision is responsible for most cent-level discrepancies during migrations.
Automated Invoice Runs
Veloxiom generates a full monthly invoice run for all active services on a scheduled day, applies proration, produces a PDF, and submits to e-invoicing where it is required. Invoices can also be created manually for one-off work, and proforma documents are supported for customers who pay before the invoice is issued.
Collection Without Chasing
An automated invoice that arrives by email and waits for a manual bank transfer has moved the work, not removed it. Collection is where automation actually pays for itself.
Direct debit (ΔΙΑΣ in Greece, SEPA elsewhere)
Direct debit is the highest-value automation available to a small ISP because it converts collection from an action into a default. Practical points that are easy to get wrong: mandates are legal documents and must be stored with their date and identifier; submission files have to be generated on the bank's schedule, not yours; and rejections come back as a return file that must be processed automatically, otherwise a rejected charge silently looks like a successful one.
Cards and payment links
Cards are useful for reconnection because the money arrives in seconds. Recurring card payments fail more often than direct debits — expiry, limits, 3-D Secure challenges — so a retry policy is mandatory: retry a small number of times, on spaced days, and stop. Retrying daily forever is how you get charged back.
Reconciliation is the real prize
Every payment has to be matched to an invoice without a human reading a bank statement. That requires a payment reference on the invoice that the payment carries back. If you automate nothing else, automate this.
Dunning and Suspension That Does Not Lose Customers
Suspension is the most dangerous automation in the platform: it is the one that can cut off a paying customer. Build it defensively.
- Grace period. Never suspend on the due date. Payments in transit and bank cut-offs mean money frequently arrives one to three days late through no fault of the customer.
- Escalating notices. A reminder before the due date, one after, then an explicit warning that names the suspension date. A customer who was warned rarely disputes.
- Restrict before you disconnect. Redirecting the subscriber to a portal that explains the situation and offers immediate payment is far more effective than a dead connection, which most people interpret as a fault and report as one.
- Exemptions. Disputed invoices, agreed payment plans and critical accounts must be excludable individually and permanently visible as such.
- Never suspend anything that carries emergency calls without checking your regulator's rules first.
How Enforcement Works Technically
On a PPPoE network, suspension should be a RADIUS operation, not a router edit. The subscriber's session is either disconnected or, better, moved by a Change-of-Authorization to a restricted profile: minimal bandwidth, a walled garden that reaches only your payment page, and DNS redirection to a captive portal that explains the balance owed. Because the state lives in RADIUS, reconnection is the same operation in reverse and takes effect on the next session — with no manual work on the router and no risk of a forgotten firewall rule left behind.
Reconnection must be automatic and immediate. If the payment gateway confirms at 23:00, the subscriber should be online at 23:00. A customer who pays and then waits until business hours will call, and that call costs more than the automation did.
What to Automate First
In order of hours saved per hour of setup:
- Payment reconciliation — highest return, lowest risk.
- Invoice generation and delivery — high return, moderate risk, mostly about getting the rules right once.
- Reminders — no risk at all and it directly improves cash collection.
- Direct debit — largest structural improvement, needs bank onboarding.
- Reconnection on payment — cheap to build, removes the most frustrating class of support call.
- Automatic suspension — last, always, and behind a switch you can turn off.
How to Verify It Before You Trust It
Run the automation in parallel with your current process for one full cycle and compare, invoice by invoice. Specifically check: subscribers activated mid-month, subscribers who changed plan mid-month, cancellations, credit notes, zero-price and free accounts, and anyone with a manual discount. Those six cases contain nearly every proration and VAT bug you will ever have. Then run the suspension logic in a reporting-only mode — produce the list of subscribers it would suspend and read it. The first time, that list almost always contains someone it should not.
Frequently Asked Questions
How much time does automated ISP billing actually save?
For a provider with a few hundred subscribers, the invoice run itself is a couple of hours a month; reconciliation and chasing payments is usually several times that. The reduction comes mostly from reconciliation, reminders and automatic reconnection, not from generating the invoices.
Should suspension be automatic?
Eventually yes, but only after a full cycle in reporting-only mode, always with a grace period, and always with per-customer exemptions. Restriction to a captive portal is safer than disconnection because it explains itself to the customer.
What is the difference between a proforma and an invoice?
A proforma is a payment request and carries no tax obligation; an invoice is a tax document with a legally controlled number. Providers who require payment before activation usually issue a proforma and then the invoice once the money arrives.
Can I keep billing manually and only automate enforcement?
It is possible but it is the wrong order. Enforcement acts on balances, so if the balance is maintained by hand, an automated suspension will act on stale data — which means disconnecting customers who have paid.
Related Reading
- Captive portal and subscriber suspension — how restriction works in practice.
- ΑΑΔΕ myDATA e-invoicing for Greek ISPs — the compliance half of billing.
- MikroTik RADIUS authentication setup — the CoA mechanics behind enforcement.
- Comparing ISP platforms — what to ask before you migrate.