Blogs

SAP S/4HANA Migration: A Practical Guide for UK Businesses

If your business runs on SAP, an SAP S/4HANA migration is one of the biggest digital changes you’ll make in the next few years, and with SAP ECC’s mainstream maintenance ending in 2027, it’s not a decision you can put off indefinitely. Done well, it’s a chance to modernise your processes, simplify your data model, and build a genuine platform for growth. Done badly, it’s an expensive way to move your old problems into a new, less forgiving system.

This guide covers the ground most businesses need before they start: what the migration actually involves, the key commercial and technical decisions you’ll face, what it costs and how long it takes, and the challenges most likely to derail it. One of those challenges gets more attention here than you’ll find in most migration guides, because it’s the most common and the most preventable… your data. Carry duplicate records, outdated materials, or inconsistent customer entries into S/4HANA, and you’re not transforming anything. You’re just putting bad data into a new system and expecting better results.

What is an SAP S/4HANA migration?

An SAP S/4HANA migration is the process of moving a business from an older SAP ERP system (typically SAP ECC) onto S/4HANA, SAP’s current-generation ERP platform built on the in-memory HANA database. It’s more than a version upgrade. S/4HANA uses a simplified data model, a different user interface (SAP Fiori), and real-time reporting instead of the batch processing most ECC users are used to. Most migrations involve some redesign of processes and data structures, not just a technical lift-and-shift of what you already have.

There are two decisions that shape almost everything else about your migration: which SAP commercial programme you go through, and which technical approach you use to get your data and processes across. Both are covered below.

The key decisions you’ll need to make

RISE with SAP vs GROW with SAP: choosing your commercial route

Before you get into the technical approach, SAP will steer you toward one of two packaged offerings, and it’s worth understanding the difference early because it affects contract structure, infrastructure, and which technical path fits.

RISE with SAP is aimed at existing SAP customers, typically those already running ECC, who want a guided transformation to S/4HANA Cloud Private Edition. It bundles the software, hyperscaler cloud infrastructure, migration tooling, and business process transformation services into a single contract, with incentives designed to protect the investment you’ve already made in your current SAP landscape. It’s the natural fit if you’re doing a system conversion or a larger, more involved transformation of an existing estate.

GROW with SAP is aimed more at businesses moving to S/4HANA Cloud Public Edition for the first time, or those who want a faster, more standardised start. It’s built around preconfigured, best-practice business processes and a guided implementation methodology, which makes it a common fit for new implementations rather than conversions of an existing system.

Neither programme removes the need for the data and process decisions covered in this guide; they change the commercial and infrastructure wrapper around your migration, not the underlying work of getting your business ready.

Greenfield vs brownfield vs selective: choosing your technical approach

This is the decision most migration guides lead with, and for good reason — it determines how much of your existing data, process, and complexity you carry forward.

System Conversion (Brownfield) is a technical upgrade of your existing ECC system to S/4HANA. It keeps your business processes and historical data intact, which is appealing if your current setup works well and you want minimal disruption. But it also carries over your data exactly as it is: duplicates, inconsistencies, legacy records, and any workarounds built up over time. Without a thorough data cleansing and governance effort before conversion, you’re lifting and shifting years of accumulated issues into a new system.

New Implementation (Greenfield) is a fresh start. You build a new S/4HANA system from the ground up, giving you the chance to redesign processes, standardise templates, and enforce clean data structures from day one. It suits organisations that want to leave behind complexity, or that are undergoing major business transformation anyway, but it requires careful planning around what data to bring across and how to avoid introducing poor-quality legacy records into an otherwise clean environment.

Selective Data Transition (Hybrid) sits between the two. It lets you move only the data and processes you want, specific company codes, master data domains, or recent transactional data, which suits businesses with multiple SAP instances or those consolidating regional systems without losing critical history. It still depends on a strong data strategy to decide what’s worth keeping.

	System Conversion (Brownfield)	New Implementation (Greenfield)	Selective Data Transition (Hybrid)
Best for	Businesses whose current processes already work well	Businesses wanting a clean break from legacy complexity	Businesses with multiple SAP instances or partial consolidation needs
Historical data & processes	Carried over as-is	Rebuilt from scratch	You choose what moves
Typical speed to go-live	Generally fastest	Generally slowest	Varies by scope
Data risk	Inherits existing data issues in full	Lowest risk if cleansing happens pre-migration	Moderate — depends on what’s selected
Effort required	Lower technical effort, but data cleansing is still essential	Higher effort — new design, data mapping, testing	Higher planning effort to define scope correctly

In all three, clean and governed master data is a constant requirement. No migration tool, however advanced, prevents data issues from reappearing in S/4HANA if they’re not addressed at the source.

How long does an SAP S/4HANA migration take, and what does it cost?

Timelines and costs vary widely depending on company size, data volume, and how much customisation exists in your current system, but as a general guide:

System conversion (brownfield): often 6–12 months for a mid-sized business
New implementation (greenfield): typically 12–24 months, given the scope of redesign involved
Selective data transition: usually falls somewhere between the two, depending on scope

Cost follows a similar pattern. Brownfield is usually the cheaper route on paper, but that gap narrows, or reverses, once you account for the cost of migrating bad data and then fixing it after go-live. Businesses that budget properly treat data cleansing as a line item from day one, not a contingency they hope not to need.

The top challenges in an SAP S/4HANA migration

Most of the risk in an S/4HANA migration isn’t in the software itself; SAP’s tooling for the technical move is mature and well-documented. It’s in everything around it:

Data quality and complexity: covered in depth below, because it’s the one most businesses underestimate
Custom code compatibility: code built for ECC doesn’t always transfer cleanly, and some of it will need rework or retirement
Technical integration: connections to other systems (CRM, warehouse, e-commerce, and increasingly SAP BTP for extended analytics and integration; see our guide to SAP BTP) need to be re-tested, not assumed to carry over
Cost and resourcing: internal teams are often running the migration alongside their day jobs, which stretches both budget and goodwill
Business process complexity: the more bespoke your current processes, the more redesign work a migration requires
Testing and QA: validating against real business scenarios, not just confirming the data loaded
Downtime: for many businesses, especially those running 24/7 operations, minimising disruption during cutover is as important as the technical outcome
Change management: new interface, new processes, and sometimes new ways of working; user adoption is a project workstream in its own right, not an afterthought

Any one of these can derail a timeline or blow a budget. But one shows up more often than the rest, causes more downstream damage, and is more preventable than any of them — which is why it gets its own section.

Why bad data is the challenge most businesses underestimate

One of the most common pitfalls in any S/4HANA migration is assuming the new system will automatically resolve problems created by poor data in the old one. It won’t. If anything, S/4HANA exposes bad data more clearly and makes its consequences more severe.

Duplicate customer or vendor records don’t just clutter the system; they create confusion in finance, procurement, and sales. One department may use one version of a supplier, another a second, with different payment terms or contact details. Inconsistent material descriptions can cause incorrect inventory reporting or product selection, which then affects logistics, planning, and customer fulfilment.

Over time these issues compound. Processes that were supposed to be faster in S/4HANA get delayed because users aren’t sure which records to trust. Automation breaks when workflows encounter data they weren’t built to handle. Reports meant to guide strategic decisions produce conflicting results. At best, users lose faith in the system. At worst, the business rebuilds the manual workarounds the migration was meant to eliminate.

There’s a regulatory dimension too. In sectors like life sciences, food and beverage, or manufacturing, incorrect product master data can cause compliance breaches — auditors expect clear traceability, accurate documentation, and controlled master data changes, and S/4HANA can only deliver that if the inputs are reliable from day one.

And even setting the operational impact aside, bad data simply makes migration itself more expensive. Poor-quality records take longer to map, clean, test, and reconcile, increasing the likelihood of rework and delay. Once live, they generate more support calls, more change requests, and more time spent correcting rather than improving. For a business investing heavily in an ERP transformation, that’s a costly way to start.

Thinking this through for your own migration? We run master data assessments that show you exactly where the risk sits in your current data, before it becomes a go-live problem. Get in touch to talk it through.

When should data preparation begin?

Far earlier than most teams think. Cleaning up master data isn’t a quick task, and it’s where your focus should be from the moment the migration kicks off. It involves identifying and merging duplicates, fixing gaps, standardising values, and agreeing on ownership, none of which can be done in the final weeks of a project. Ideally, it begins as soon as the decision to move to S/4HANA is made.

Treating data as a late-stage activity is one of the most common mistakes in SAP transformation projects. Do that, and you’ll either delay go-live or carry over avoidable issues that cost far more to fix later.

How to prepare your master data for S/4HANA

Preparing for S/4HANA isn’t only about choosing the right migration approach or managing technical infrastructure — it’s about making sure your core business data is in the best possible shape before it lands in the new system. Without this, even the most advanced system won’t deliver the results you’re expecting.

Here’s what a well-prepared master data workstream should include:

Start with a full data assessment

Before anything is migrated, you need a clear picture of what exists. Profile your master data, customers, vendors, materials, assets, and so on, to identify duplicates, outdated records, incomplete fields, inconsistent formats, and usage patterns. This highlights which records are still relevant and where the biggest quality issues lie, and gives stakeholders a data-driven view of the scope and effort involved.

Clean, standardise, and enrich

Once you understand the issues, the hard work begins. Deduplicate records across systems, align naming conventions and formats, and fill in missing attributes where possible. Use validation rules to catch logically unsound data, no future birthdates in customer files, no materials with invalid units of measure. This is also a good moment to enrich data with anything S/4HANA will need that isn’t currently captured.

Define ownership and accountability

Clean data doesn’t maintain itself. Assign clear ownership for each master data domain, with defined responsibilities and workflows for approving, updating, and monitoring records. If a product description needs to change, who signs it off? If a new supplier is added, who checks the data is complete and compliant? These roles need establishing before go-live, not discovered afterwards.

Rationalise and archive legacy records

There’s no point migrating data that hasn’t been used in years. Apply filters to identify inactive customers, suppliers, or products, and set rules for what gets archived instead of migrated. Focus effort on records that support current and future operations, not long-closed transactions.

Test with real data scenarios

As your new system is built and tested, validate against real master data, not just clean test cases. This is how you spot where formats don’t align, where logic needs adjusting, or where business processes are still leaning on old, unstructured information.

Automate wherever possible

Manual cleansing works at small volumes, but it doesn’t scale. Tools like Maextro automate key steps, identifying duplicates, managing workflows and approvals, and because it’s built for SAP environments, it fits naturally into both ECC and S/4HANA landscapes, letting you prepare clean, structured master data without reinventing how your teams work.

Best practices for a smooth SAP S/4HANA migration

Every successful S/4HANA migration has one thing in common: preparation. That means putting the right people, processes, and tools in place early, so your business doesn’t carry today’s problems into a more powerful, but less forgiving, system.

Involve the business early. Master data lives in the business, not just IT. Procurement knows what makes a supplier record useful; sales understands how customers are actually grouped and segmented. Involve these teams during data assessments, cleansing, and testing, so the system reflects real-world needs rather than assumptions made in isolation.

Prioritise quality over quantity. Migrating every last record is rarely the right call. Focus on what’s active, accurate, and needed to support future processes — that might mean moving only the top 80% of frequently used materials, or recent customers with open orders. Set clear criteria for what stays, what’s archived, and what’s cleaned but not carried forward.

Define governance, not just clean-up tasks. Cleansing is a project; governance is a habit. If you want clean data to stay clean after go-live, you need ownership structures, data creation workflows, and approval logic embedded into business processes — use the migration as the moment to formalise and document how master data should be handled going forward.

Use automation to scale your effort. Manual fixes work for short-term cleanups but don’t scale across thousands of records or multiple data domains. Tools like Maextro automate validation, approvals, deduplication, and status tracking — the more automation you apply before go-live, the more sustainable your governance will be afterwards.

Validate in real scenarios, not just technical checks. Don’t just test whether data loads; test whether it works. Use real business scenarios to check product hierarchies display correctly, payment terms pull through on vendor records, and users can search and retrieve what they need without confusion or duplication.

Embed data ownership into the new system. Make sure that once S/4HANA is live, there’s no reversion to old habits. Build roles and responsibilities for master data maintenance into the system design, with controlled access, clear approval processes, and regular reviews.

Tools and resources for your migration

SAP provides a set of native tools to support the technical side of migration, worth knowing about even if you’re bringing in a partner to run the project:

SAP Readiness Check: assesses your current system’s readiness for conversion, flagging custom code, add-ons, and other conversion-relevant items
Migration Cockpit: SAP’s standard tool for loading and validating data into S/4HANA
SAP Landscape Transformation (SLT): replicates data in real time, often used in selective data transition scenarios

These tools handle the technical mechanics of moving data; they don’t tell you whether that data is worth moving in the first place. That’s where Maextro fits: it works alongside SAP’s native tools to handle the data quality and governance side, so what goes into Migration Cockpit is already clean rather than being cleaned up after the fact.

After go-live: keeping your data clean post-migration

Going live isn’t the finish line. Once S/4HANA is running, it’s easy to assume the data problem is solved, but without ongoing governance, the same bad habits that caused issues before migration will start creeping back in.

Build regular data quality reporting into your analytics layer or master data platform, with KPIs for completeness, duplication, and usage tracked like any other operational metric. Keep the ownership structures you defined during preparation active; someone should still be signing off new supplier records and product descriptions six months after go-live, not just in the first week. Many businesses also run a structured hypercare period immediately after cutover, a few weeks of dedicated support and close monitoring to catch and fix issues fast, before they become habits.

FAQs

How long does an SAP S/4HANA migration take?

It depends on the approach and the state of your data, but most mid-sized migrations take between 6 and 18 months. Poor-quality master data is one of the most common causes of delay, since cleansing can’t be rushed in the final weeks of a project.

What’s the difference between RISE with SAP and GROW with SAP?

RISE with SAP is aimed at existing SAP customers transforming an existing estate, typically via system conversion, onto S/4HANA Cloud Private Edition. GROW with SAP is aimed at businesses moving to S/4HANA Cloud Public Edition for the first time, using preconfigured best-practice processes for a faster, more standardised start.

What’s the difference between brownfield and greenfield S/4HANA migration?

Brownfield (system conversion) upgrades your existing ECC system in place, keeping historical data and processes. Greenfield (new implementation) builds a new S/4HANA system from scratch, giving you a clean slate to redesign processes and data structures.

When does SAP end support for ECC?

SAP’s mainstream maintenance for ECC ends on 31 December 2027, with optional extended maintenance available at additional cost through 2030. This deadline is the main driver pushing many businesses to migrate now rather than later.

Do I need to clean my data before migrating to S/4HANA?

Yes. S/4HANA doesn’t fix bad data automatically; if anything, it exposes it more clearly. Data cleansing and governance should start as soon as the migration is decided, not in the final weeks of the project.

Final thoughts

Moving to SAP S/4HANA is one of the most important steps a UK business can take toward digital transformation. But it goes far beyond another systems upgrade. It’s a total replatforming of your entire operational landscape, and success depends as much on trust as it does on technology. Trust, in any enterprise system, comes from data you can rely on.

Poor master data is one of the most common, costly, and preventable problems in an S/4HANA migration. It slows the process, causes errors after go-live, and undermines confidence in the new system. The good news is that it’s entirely fixable, but only if it’s addressed early, with the right strategy and the right tools.

That’s where data cleansing platforms like Maextro make a real difference. Built specifically for SAP environments, it helps organisations assess, cleanse, and govern their master data in a scalable, automated way, before, during, and after migration. Whether you’re cleaning up legacy customer records, validating materials data, or introducing governance around supplier onboarding, Maextro gives you the control you need to move forward with confidence.

A clean, governed data foundation won’t just make your S/4HANA project more successful; it will make your business faster, more efficient, and more resilient for years after go-live.

If you’re planning your journey to S/4HANA, don’t wait to start the data conversation. The earlier you prepare, the more value you’ll unlock.