Cost analysis
How Much Does a Legacy ERP Migration Really Cost in 2026?
The first question any finance director asks about a legacy ERP migration is the one that has no single answer: how much does it cost? The honest answer, in my experience across dozens of enterprises in the UK and Europe in 2025 and into 2026, is a wide band. Roughly £2 million to £12 million for a genuine, mid-size to large enterprise replacement, and sometimes more. Everything below is about how you land inside that band rather than blow through it.
The honest range for 2026
Do not trust a price that comes back as one tidy number. Migration cost is a portfolio of lines, each driven by different factors, and the total moves with your estate size, the number of modules, the amount of customisation and the state of your data. As a planning baseline, small and mid-market companies often land in the low millions, while larger, multi-entity, heavily customised programmes run into double figures.
The single biggest reason projects overrun is that the range is treated as a ceiling rather than a target that requires discipline. For the shape of the schedule that sits alongside this budget, see how long a full ERP replacement takes. Gartner's ERP cost and total cost of ownership research reinforces exactly this discipline.
Licence and subscription
Licences or subscriptions are the visible headline, and they move with user counts, modules and, increasingly, transaction or usage volume under cloud pricing. A realistic plan treats this as a growing curve, not a point, because implementation tends to expand demand once the system proves itself. For cloud platforms, read the user tier and integration pricing closely, as they hide recurring costs that pile up after year one. The difference between owning and subscribing is covered in legacy versus cloud ERP.
Implementation and consultancy
Implementation fees cover the configuration, process design, testing and cutover delivered by partners or internal teams. This is often the largest line after licences, and it scales with scope and with how much you choose to customise. The cheaper the day rate, the more days you will usually spend, so judge on total outcome, not on rate alone. Fixed-fee deals are possible, but they push the risk of scope creep onto the partnership, which often resurfaces as change requests later. Scope is the lever, and the way to pull it is described in choosing an implementation methodology.
The data line nobody likes
Here is where budgets quietly break. Cleaning and migrating data routinely consumes more effort than the implementation itself, and it is the line most often under-scoped. Extraction, transformation, validation, reconciliation and the business time spent making judgement calls all accumulate fast. On several of my engagements, data work alone has run to a third of the project cost.
Price this from a real audit, not a guess, and let the findings set the budget rather than the other way round. The method for doing the work at a realistic price is in our guide to cleaning master data before you migrate. If your number comes back significantly above the estimate, that gap is information, not a mistake.
One manufacturing client budgeted a modest single line for data based on a supplier's brochure. When we profiled their estate, we found three separate part-numbering schemes carried from past acquisitions. The data line grew to seven figures. The tender had to be re-baselined before a single licence was bought. Nobody enjoys that conversation, but it is cheaper than discovering it after go-live.
Internal time and hidden fees
The most invisible cost is your own people. A migration pulls skilled staff from their day jobs for workshops, testing, training and data decisions, and that capacity has a real price, whether you see it as backfill or as deferred work. Count it explicitly and you will also get an honest view of whether your key people have the time to succeed, which is why hidden ERP costs deserve a read before you price anything.
Add the smaller fees that every programme accumulates: specialist hardware or cloud, security and compliance reviews, temporary licence uplift, and the change management and training effort that determines whether the system is actually adopted. Together these hidden lines often exceed the headline implementation fee, so treat them as first-class budget items, not afterthoughts.
What drives the price up or down
Four factors move your number in 2026. Size and complexity of the estate. The degree of customisation you carry, because bespoke code converts to expensive build time. The state of your data, because dirty data multiplies effort. And the depth of change management you commit to, because the cheapest migration that nobody adopts is the most expensive of all.
A vanilla, same-vendor, cloud-first replacement on clean data can land at the lower end of the range. A heavily customised, multi-entity migration with years of dirty history will push toward the top, and no amount of negotiation changes that, because the work is real. If the price feels too high, reduce the things that drive it, the scope, the customisation, or the history you carry, rather than wish the number smaller. And before you begin any of this, it is worth asking the foundational question in is your business ready to migrate.
Frequently asked questions
How much does a legacy ERP migration cost in 2026?
For a genuine mid-size to large enterprise replacement, expect roughly £2 million to £12 million when all lines are counted, and more for heavily customised or multi-entity estates. Smaller companies can land in the low millions, but licence, data, integration and internal time usually push the true total well above the headline quote.
Why do ERP migrations cost so much?
Because the bill is more than software. It includes consultancy, licences, integration, data cleaning, internal staff time, change management and support renewals. The implementation fee is often the minority of the real total, so the apparent price understates the full investment.
What is the biggest hidden cost in an ERP migration?
Data. Cleaning, migrating and reconciling data consistently consumes more effort than the software build and is the most under-scoped line. Internal staff time is a close second, because the people who power the project are rarely counted in the budget.
How can I reduce the cost of an ERP migration?
Reduce scope and customisation, clean master data before contracting, price internal time honestly, and choose a standard product over a bespoke build. Each reduces a real driver of cost. Trying to negotiate the headline number alone rarely works because the underlying work is fixed.
Sources and further reading
The argument in this article draws on public research. Where you want to go deeper, these are the sources cited in the text and further reading.
