Every replacement of a business-critical case-management system shares one unforgiving constraint: the work does not stop. Cases keep opening. Reviews keep progressing. Deadlines keep falling due. You cannot pause a regulatory function while you swap its operating system underneath it - and you cannot afford to lose an open case, a document or a decision in the process.

This is why the transition method matters as much as the build. A beautifully configured new system that goes live on a broken cutover is worse than the legacy product it replaced. The discipline that makes the difference is proper parallel running: a controlled period in which the new service is operational while the incumbent is retired safely, with reconciliation evidence at every step. Here is how we approach it.

Migration is a rehearsal, not an event

The instinct on many programmes is to treat data migration as a single dramatic moment near go-live. That is how open cases get lost. Migration should be rehearsed repeatedly, long before cutover.

Start by profiling real data early - a sample during discovery - so you understand the shape and the flaws of what you are moving. Define cleansing rules and ownership. Build repeatable migration scripts rather than one-off manual moves. Then run dry run after dry run, each producing an exception report and reconciliation totals, until the numbers tie out every time. By the time the real cutover arrives, it should feel like the tenth performance of a well-drilled routine, not opening night.

Migration integrity is where quality tooling earns its keep. Getting case records to match, de-duplicating, validating and reconciling counts between the old and new systems is precisely the kind of data-quality work that decides whether users trust the new platform on day one. VE3 applies proven data-matching and validation capability - including our MatchX platform - to give migration a defensible, reconciled evidence trail rather than a hopeful copy-and-check.

Migrate what is live, not everything ever

The scope decision that most reduces risk is also the simplest: migrate the active open caseload and its associated documents, and treat full historic migration as a separate, lower-risk exercise. Moving a decade of closed cases on cutover weekend adds enormous volume, enormous risk and very little operational value - the live team needs its current work in the new system, cleanly and completely. Closed history can be migrated later, archived, or kept accessible read-only, according to retention policy. Narrowing the cutover to what is genuinely live is one of the biggest levers on a safe transition.

Decide, in advance, which system is the source of truth

Parallel running fails when nobody has said which system is authoritative for which activity. Run two live systems without that ruling and you get duplicate data entry, contradictory records and reporting that no one believes.

So agree it explicitly before the parallel period begins: from cutover, the new system is authoritative for new and migrated open cases; the legacy system is read-only reference for anything not migrated. Minimise duplicate entry wherever possible. Where some overlap is unavoidable, define exactly which comparison samples you will check and how you will reconcile key reports between old and new. Log every discrepancy against an agreed rule. The goal of the parallel window is not to run everything twice - it is to build the evidence that lets you retire the incumbent with confidence.

Reconcile reporting, not just records

A subtle trap: the records migrate perfectly, but the new system's reports don't match the old ones, and trust evaporates. Regulatory bodies run on their numbers - cases opened and closed, enquiry rates, correction volumes, ageing and workload. If those figures move when the system changes, people assume the data is wrong even when it isn't.

Pre-empt this by defining a governed set of key performance indicators with an agreed source, formula, owner and reconciliation method for each - and by comparing the critical outputs across both systems during parallel running. When the new dashboard and the old report tell the same story, you have earned the right to switch the old one off.

Govern the cutover with objective go/no-go criteria

The moment of cutover should be the least dramatic part of the whole programme, because everything has been decided in advance. That means named business and technical decision-makers, a cutover runbook, explicit go/no-go criteria, and continuity and rollback arrangements ready in case anything material fails. Nobody should be improvising on the day.

This is delivery discipline borrowed from the most demanding environments - the kind of business-critical service transition where a live public service must be replaced by a fixed date without any loss of service, evidence, knowledge or control. Phase entry and exit criteria, configuration and release control, reconciliation evidence, runbooks and a known-error record are not bureaucracy. They are what turn "we think it worked" into "we have proof it worked."

Then, and only then, retire the incumbent

Parallel running ends not on a date but on evidence. When the new service has run stably, when case and reporting outputs reconcile against the legacy system, and when users are working confidently in the new environment, you have what you need to switch the old arrangement off - and to demonstrate to any auditor exactly why it was safe to do so.

Handled this way, the scariest phase of a case-management replacement becomes its most reassuring. Not a leap of faith, but a rehearsed, reconciled, evidenced handover - with every open case exactly where it should be.

VE3 delivers fixed-date case-management transitions on Microsoft 365 and Power Platform, with migration, reconciliation and parallel-running discipline built in. Talk to us about de-risking your switchover.