Leaving Someone Else's Systems Is Not a Weekend. It Is a List, Then One Module at a Time.

Two years ago your business was bought out of a larger group. The systems stayed where they were.

Your tills, your stock and your accounts still run on the group’s systems, under an agreement that lets you use them for a fee until a set date. That date is fourteen months away. The fee rises next year.

The plan on the table is to build everything new and switch across on one weekend, just before the date.

What We Found

We went through the public record: the best-documented case of a retailer leaving a former owner’s systems, and one case of a business stopped by an account outside its control.

Leaving a former owner’s systems is a large project in its own right. A large UK grocer moved off thousands of older systems it had shared with a former owner, onto a packaged ERP product on a public cloud. By the end of 2025 the work had cost it more than £1 billion.

It can reach the shelves. Sales in the second half of 2025 were hit by disruption to what was on the shelves and to shopping online, and its leadership said the work delayed its recovery.

Not knowing who holds an account can stop trading in a day. At a small Indian grocery delivery start-up, access came through the account of someone who had left, in mid-2025, and it lost its app code and its servers. Afterwards its app stayed up but could not take orders. This is access control at a start-up, not an old system, and the record does not say who did the wiping.

What a Staged Move Opens Up

Our reading is that a separation is a set of systems to be moved one after another, not a date to be met.

• The date becomes the end, not the event. Every module moved early is one that will not be moved in a rush.
• You learn early whether the date can be met. A staged plan made now shows, while there is still time to act, whether the stages fit before the date.
• The new systems are in your name. Each one lands in accounts your firm opens, so the firm does not leave one holder only to depend on another.

This is our reading. It is not a measured market figure.

Three Ways to Leave Someone Else’s Systems, Weighed

Option	When it fits	What it risks
Build everything new and switch on one weekend before the date	The old systems are few and simple, and the firm knows what they do	Everything nobody listed arrives at once, in front of customers, with no old system to go back to
Ask the holder for more time and keep paying	The holder is willing, and the firm needs time to plan	The fee goes on, the terms are the holder’s, and nothing is learnt about the systems while the clock runs
Write down who holds what, arrange read-only access to the code, write the specification, then rebuild one module at a time in accounts in the firm’s own name	The systems matter to trading, and there are months before the date	You pay the old holder and for the new work at the same time. It takes more months than a single switch, so it must start early

Where You Are Now, and Where You Should Be

This is the benchmark we would set before the first module moves, and fill in as each module is accepted.

Measure	Typical starting point	Where it should be	How it is checked
Systems, with whose name holds each account, code repository and domain	Not recorded; known to whoever set them up	Every system listed, a list for the firm to act on	The list beside the map of the system
Read-only access to the code	With the holder; not asked for	Arranged by the firm for every system to be assessed	Confirmed before the assessment begins
Modules rebuilt in accounts in the firm’s own name	None; everything in the holder’s	Rising at every stage, each module accepted before it takes over	Reported at every review, with the traceability matrix
The specification	Held by nobody; in the holder’s heads	Held by the firm, and updated with each accepted module	The specification
The cost of leaving	One sum, committed at the start	The old holder’s fee and the new work both in the plan, stage by stage	The cost comparison beside the staged plan
The leaving date	One weekend, just before it	The last stage before the date, or the firm told early that it will not fit	The staged plan set against the date

The starting points above are what we expect to find. In an engagement they are replaced by your own position, taken in the first review. The targets are what we would work towards with you. They are not results we have already achieved for a retailer.

A small part of the finished list might look like this.

System	Whose name holds it	Status
Stock records	The former owner’s account; code held by the former owner	Stage 1: rebuilt in the firm’s own account and accepted; off the old system
Online shop	The agency’s hosting account; code with the agency; domain in a former employee’s name	Read-only code access arranged by the firm; the firm is moving the domain into its own name
Till links to accounts	The former owner’s account	Stage 2: still on the old system until its module is accepted

The rows above are an illustration, not taken from a real business.

How We Work With You, and What You Are Left With

1. We listen: a free Reliability Review. A first conversation about the systems you are leaving, who holds them and the date you are working to. You leave with a short written note of what we found. You can start with a conversation about the system; we ask for read-only code access only when the assessment begins.
2. We research. We research your sector, the regulator’s position and what the public record says about firms in your situation.
3. We read the system and propose: the Legacy System Specification Assessment. Here the system is the applications your business built or had built, wherever they are held. It produces a map of the system as it stands, a written specification of what it does, a risk register, a cost comparison between keeping and replacing the system, and a staged plan with a fixed quote. AI does a first pass, our senior engineers review it and trace it to the code, and your own experts confirm it. Code access is read-only and logged, never used for training, and deleted within 30 days of the evaluation ending unless we engage.
4. If you approve, we build. We replace a system one module at a time while the old one keeps running. Here that means the firm’s own applications, rebuilt module by module in accounts the firm opens in its own name. We never do a single cutover. A traceability matrix links every old function to its replacement. The work is billed by milestone, each milestone tied to a module you accept, and you can pause after any accepted module.
5. We review against the benchmark. Before work starts we set the benchmark above. As each module is accepted we show you where each measure stands, and the filled-in benchmark is yours at the end.

The Review is free. Every paid step is fixed price, agreed at scoping. Stop after any step. The findings are yours. The assessment fee is credited in full against the first build stage if it starts within 90 days of the report.

This has a price. You pay the old holder’s fee and for the new work at the same time. Running old and new side by side needs data to pass between them, and that depends on what the holder will allow. A staged move takes more months than a single switch; begun too late, it will not finish by the date, and we will say so if the plan shows it. Where the systems you are leaving are packaged products, our part is limited to the applications built around them; we do not install, move or choose them, and we do not host or secure systems. We do not recover accounts, domains or code, we do not negotiate, and we give no legal advice; arranging access with the holder is your step. We have no published case of this work for a retailer.

At the end you hold the specification, the traceability matrix for every module we rebuilt, and modules that run in accounts in your firm’s own name.

What changes for the business:

Role	What they gain
CEO	Independence is reached one part at a time, with no single weekend that puts trading at stake.
CTO or CIO	Each part is rebuilt in the firm’s own account while the old one keeps running.
CFO	The cost of separating is committed stage by stage, not in one sum.
CISO	Each part that moves lands in an account the firm controls, with access the firm sets.
COO	Orders and dispatch keep working while systems change hands one at a time.

The cases in this article, and what IOanyT does about that kind of problem:

The case	What IOanyT does
A large UK grocer’s move off thousands of older systems it had shared with a former owner cost more than £1 billion by the end of 2025, and sales were hit by disruption.	Our part is far narrower than this case. We do not implement packaged ERP products, and we do not say why that project cost what it did. For applications a retailer built or had built, we rebuild one module at a time in accounts in the retailer’s own name, with the old system still running and each module accepted before it takes over.
At the small Indian grocery start-up, access came through the account of someone who had left, and its app stayed up but could not take orders.	Our part is narrower than this case. We do not manage access or remove a leaver’s account. What we rebuild runs in accounts the firm opens, where the firm’s own people set who has access.

IOanyT is a consultancy with its own engineering team: we study the problem, recommend, and prove it by building only what you approve. The date is someone else’s; how much has already moved when it arrives can be yours.

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