When your CIS and ERP are both nearing end-of-life, how to decide which to replace first and protect the GL interface between them.
For US Utilities serving 3,000-100,000 meters and for operations team, billing team and utility managers. For Heads of Billing who own collections accuracy and revenue leakage.
When existing CIS and ERP systems are aging and nearing end-of-life at the same time, the decision is no longer whether to replace them but in what order. Because the CIS posts revenue into the ERP general ledger, replacing one changes the other, so utilities need a sequenced plan: document lifecycle dates and dependencies, choose whether the CIS, the ERP, or both move first, and protect the interface between them throughout. A modern customer information system that integrates with any ERP removes the need to replace both at once. This guide covers how to plan that sequence.
Is your system end-of-life, or just old?
An old system can run for years. An end-of-life system is one the vendor has scheduled to stop supporting. The difference matters because each lifecycle stage removes something specific.
For a utility, end-of-life usually shows up as one of these:
The operational risks of running past that point, such as revenue leakage, security exposure, and audit findings, are covered in the guide to the risks of outdated utility billing software. This guide focuses on what to do when the CIS and the ERP reach that point together.
Many utilities bought their CIS and ERP in the same period, from vendors whose products were built to work with each other. Some CIS products even run on top of an ERP platform. That shared history means the two systems tend to reach end-of-life in the same window, and each one depends on the other.
A current example is Microsoft Dynamics GP, a common accounting system at small and mid-size utilities. According to Microsoft's end-of-support announcement, mainstream support ends December 31, 2029, and security updates stop on April 30, 2031. If your CIS runs on GP or depends on a GP integration, that date applies to your CIS planning too. The ERP side of that move is covered in the Microsoft Dynamics GP migration guide.
Sequencing decisions go wrong when they are made on assumptions. Before choosing an order, write down:
This list usually shows that one system has less time left than the other. That system sets the deadline, and the other system's plan has to fit around it.
Which system is closest to losing security updates, and which one would hurt more if it failed?
There are three practical orders. Each one fits a different situation.
For most small and mid-size utilities, the lowest-risk order is the one that replaces the system with the nearest hard deadline first, using a replacement that connects to any ERP through standard integrations. That way the second project does not force rework on the first. Replacing both together makes sense mainly when the CIS cannot run without the old ERP.
Do you know which interface between your CIS and ERP would break first if either system changed?
Work through the plan in this order:
The step utilities most often skip is step 4. When GL mapping is decided late, the second project reopens decisions the first project already made. Making the case for funding to a board is covered in the guide to building a business case for utility software.
Replacements take time, and the old systems have to keep working until cutover. While they do:
Moving data and history off the old platform is the part of the project with the most technical risk. What that migration involves, and how utilities reduce disruption to billing, is covered in the guide to migrating legacy utility systems to the cloud.
SMART360 is a cloud CIS and billing platform for utilities serving 3,000 to 100,000 connections. It replaces the CIS side of an aging stack and connects to the ERP you run today or the one you move to next, so the CIS project does not have to wait for the ERP project.
Island Water Authority replaced its legacy billing system with SMART360 and reported 92% fewer billing errors after the move. The honest boundary is accounting: SMART360 does not replace your ERP, so the ERP decision still needs its own plan. What SMART360 removes is the need to replace both at the same time.
It means the vendor has scheduled a date to stop supporting it. Before that date, support usually narrows to security patches only; after it, the software may still run but receives no fixes, security updates, or vendor help. For a utility, that creates security, audit, and compatibility risk, and makes each interface between systems harder to keep working.
Replace the system with the nearest hard deadline first, especially if it stops receiving security updates sooner. Choose a replacement that connects to any ERP through standard integrations, so the second project does not force rework. Replace both together only if the CIS cannot run without the old ERP, such as when the CIS is built on the ERP platform.
Utilities often bought both in the same period from vendors whose products were designed to work together, and some CIS products run on an ERP platform. The systems also share GL posting, reconciliation, and reporting, so a change in one affects the other. That shared history and dependency puts both on similar lifecycle schedules.
According to Microsoft, mainstream support for Dynamics GP ends December 31, 2029, and security updates continue only until April 30, 2031. Utilities that use GP as their ERP, or run a CIS that depends on GP, should plan replacement well before those dates.
No. SMART360 replaces the CIS and billing side, including customer accounts, billing, meter data, and the customer portal, and handles revenue, AR, journal entries, and GL mapping. It is not a full accounting suite, so payroll and full financial statements stay in your ERP. SMART360 connects to the ERP you have now and the one you move to later.
When existing CIS and ERP systems are aging and nearing end-of-life together, the deadline that arrives first will make the decision if you do not. Confirm the dates, map every interface, choose a sequence, and settle GL mapping before either new system is configured. Replacing the CIS with a platform that connects to any ERP lets each project run on its own timeline. How billing and ERP should exchange data once both are modern is covered in the guide to automating utility bill and ERP integration. To see how SMART360 replaces an aging CIS without waiting on the ERP, book a demo.
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