SAP IS-U to S/4HANA Utilities
Cohash takes SAP IS-U on ECC 6.0 to SAP S/4HANA Utilities. Custom billing schemas, variant programs and enhancements get inventoried first. Customers move to the business partner model, device and installation data gets checked, and we decide which add-ons the S/4HANA 2025 core can replace. Nothing cuts over until parallel billing on the same meter reads and FI-CA reconciliation to the ledger have proved it.
- 01Readiness and custom code scan
- 02Business partner and master data
- 03Billing and add-on design
- 04Conversion rehearsals
- 05Parallel billing and cut-over
The story
Told without the client's name or anything that could identify them.
An energy retailer ran SAP IS-U on ECC 6.0 with custom billing schema steps and variant programs written by people who had long since left, and finance reconciled FI-CA to the general ledger by hand each month-end. ECC's 2027 end of mainstream maintenance set the deadline, and the conversion window had to avoid rate cases and peak billing months. We inventoried the billing customizations and add-ons first and decided which ones the S/4HANA 2025 core replaces. After business partner conversion, device and installation data cleanup and repeated rehearsals, both systems billed the same meter reads for a full cycle, and cut-over happened between cycles with every difference explained.
why it was urgentIS-U runs on SAP ERP 6.0. Its mainstream maintenance ends at the end of 2027, with optional extended maintenance to the end of 2030. SAP says S/4HANA 2025 puts market process management and prepayment in the core, which matters if those run on add-ons today. And a 13 October 2026 update lets SAP ERP, private edition subscriptions run to 31 December 2035, with prerequisites.
- openWhoever wrote the custom billing schema steps and variant programs left years ago.
- recurringMarket communication and prepayment run on add-ons. S/4HANA 2025 may replace them.
- blockedOutsorted bills pile up each cycle and nobody wants to convert the backlog.
- openFinance reconciles FI-CA to the general ledger by hand at month-end.
- recurringThe conversion window has to avoid rate cases and peak billing months.
The estate, before and after
Before: IS-U on ECC 6.0 with custom billing variants
IS-U took the meter reads and billed them through variant programs nobody had documented, with add-ons for market messages and prepayment. Bills outsorted every cycle. FI-CA was reconciled to the ledger by hand.
Read the diagram as text
- Meter reads → SAP IS-U on ECC 6.0: meter reads
- Custom billing variants → SAP IS-U on ECC 6.0: billing steps
- Market process add-ons → SAP IS-U on ECC 6.0: market messages
- SAP IS-U on ECC 6.0 → FI-CA: billing documents
- SAP IS-U on ECC 6.0 → Outsorted bills: outsorting
- FI-CA → General ledger: manual reconciliation
After: billing on SAP S/4HANA Utilities
Now meter reads are billed in S/4HANA Utilities, with market processes and prepayment in the 2025 core. Customers sit as business partners, and a written procedure reconciles FI-CA postings to the ledger.
Read the diagram as text
- Meter reads → SAP S/4HANA Utilities: meter reads
- Market processes and prepayment → SAP S/4HANA Utilities: market messages
- Business partners → SAP S/4HANA Utilities: contract accounts
- SAP S/4HANA Utilities → FI-CA: billing documents
- FI-CA → General ledger: reconciled postings
How we run it, phase by phase.
5 phases take you from SAP IS-U on ECC 6.0 to SAP S/4HANA Utilities. Each one ends with something you can check before the next starts. As you scroll, the blocks show the estate moving across.
- phase 01
Readiness and custom code scan
Run the simplification item checks and a custom code analysis first. Then list the billing schemas, variant programs, enhancements and add-ons, each with a decision.
- phase 02
Business partner and master data
Plan customer-vendor integration to business partner. Clean device, installation and premise data before the conversion ever runs.
- phase 03
Billing and add-on design
Push custom billing steps back to standard where possible, and settle which market process and prepayment add-ons the 2025 core makes redundant.
- phase 04
Conversion rehearsals
Keep converting production copies. Time each run, fix what breaks in data and code, and stop when downtime fits the window you agreed.
- phase 05
Parallel billing and cut-over
Bill the same reads on both systems for at least one full cycle, explain every difference, reconcile FI-CA to the ledger, then cut over between cycles.
What the client got
What changed for the client once the work was done. Described, not scored: we don't publish client figures.
- result 01
Tariff logic is proven on real bills
We billed the same meter reads in both systems for at least one full cycle, and billing and finance signed off every difference before cut-over.
- result 02
Add-ons the 2025 core covers are retired
Market process and prepayment add-ons were retired wherever S/4HANA 2025 covers them in the core. We followed the add-on retirement plan.
- result 03
Customers are business partners with clean device data
Customer-vendor integration created the business partners, and the device, installation and premise data were cleaned before the conversion ran.
- result 04
FI-CA reconciles to the ledger by procedure
Month-end used to mean finance reconciling FI-CA to the general ledger by hand. Now there's a documented procedure instead.
- result 05
Collections never ran on two systems
We kept dunning and payments on one system throughout parallel billing, so customers didn't get double letters or missed clearing.
Risks we plan for
-
Hidden logic in billing variants
Custom variant programs often carry tariff rules nobody documented. Comparison bills on real accounts are the only way to prove they still work.
-
Business partner conversion errors
Duplicate or incomplete customer records either block the conversion or create wrong contract accounts. Clean-up has to start months before the first rehearsal.
-
Collections split across systems
Running dunning or payments on two systems at once causes double letters and missed clearing. Collections stay on one system throughout.
-
Downtime longer than the window
Large billing and FI-CA tables can push conversion past a weekend. Rehearsal timings decide the real cut-over plan.
Where AI helps, and where it needs guardrails
SAP says S/4HANA 2025 adds Joule-powered conversational search, and it has released a Utilities Customer Self-Service Agent for S/4HANA Utilities. We pilot that agent on a narrow set of customer requests, with a person to hand off to. Coding agents help read custom billing ABAP during the code scan, but every change gets reviewed, and any MCP access to billing data is read-only and logged.
forward deployed engineers →What you're left with
We write these for your setup, and they're working documents. Your team should be able to keep things running from them long after we've gone.
- inventory01
Custom billing schema, variant and enhancement inventory with decisions
yours to keep - plan02
Business partner conversion plan and data clean-up results
yours to keep - plan03
Add-on retirement plan against the S/4HANA 2025 core
yours to keep - tests04
Conversion rehearsal timings and downtime plan
yours to keep - document05
Parallel billing results with every difference explained
yours to keep - document06
FI-CA to general ledger reconciliation procedure
yours to keep
Platforms and services on this move
Certified engineers, wherever you need them.
Some clients want a project team, some want a couple of engineers on theirs. Either works. Onsite, nearshore or offshore, with handovers across time zones that keep things moving.
Onsite
Engineers at your sites in the US
Nearshore
Overlapping hours with US teams
Offshore
Overnight progress on your backlog
All time zones
Coverage handed over across time zones
01Should we convert now or use the private edition transition option?
Your contract, your database and the regulatory calendar decide it. The transition option does buy time, at a cost and with prerequisites. We put both routes against your rate cases and peak billing months.
02Is this a system conversion or a new implementation?
Most utilities convert to keep their history and configuration. Heavy custom billing can tip it toward a selective or new build, and the custom code inventory usually settles the question.
03How many billing cycles should run in parallel?
At least one full cycle. More if seasonal rates or estimation rules change through the year. Billing and finance explain and sign off every difference.
04Do you also work on BRIM and FI-CA?
Yes, and they often belong in the same program. We plan Convergent Charging, Convergent Invoicing and FI-CA together with the IS-U conversion.
Often on the same roadmap
AD FS federation to Entra ID authentication
Converting federated domains from AD FS to Entra ID cloud authentication, moving relying parties app by app and retiring the AD FS farm.
read the case study
Apache Airflow 2 to Airflow 3
Upgrading self-managed Apache Airflow 2, now past end of life, to Airflow 3, and fixing removed features, auth and scheduling changes before DAGs move.
read the case studyAuth0 Rules and Hooks to Actions before end of life
Rewriting Auth0 Rules and Hooks as Actions before their 18 November 2026 end of life, with token claims compared before and after each change.
read the case studyced8ed47 - 01SAP News: maintenance to 2040 and Business Suite 7 dates (4 Feb 2020)news.sap.com ↗
- 02SAP Community: Utilities topic page (S/4HANA 2025, Joule, self-service agent)pages.community.sap.com ↗
- 03SAP News: SAP ERP, private edition, transition option updates (updated 13 Oct 2026)news.sap.com ↗
Planning this move?
A 30-minute working session with a senior engineer. No slides.
- The platform and the version you're on
- Where you need to get to, and by when
- What's custom: rules, plugins, integrations
- Any audit finding or deadline driving it