SAP S/4HANA Upgrade Services in the United Kingdom

The main risks typically involve dependencies between the SAP release and the surrounding technology and business environment.

Common upgrade risks include:

• Custom code incompatibility
• Deprecated or changed SAP functionality
• Third-party add-on compatibility
• Integration and interface failures
• Data inconsistencies
• Authorisation and role issues
• Fiori application changes
• Batch job failures
• Reporting differences
• Performance issues
• Insufficient regression testing
• Production downtime and cutover problems

Risk control starts with an assessment of the current landscape. Custom code, add-ons, interfaces, business-critical processes, and data dependencies should be identified before remediation and testing begin.

Multiple testing cycles should then cover technical functionality, integrations, financial postings, reporting, authorisations, and end-to-end business processes.

Downtime depends on the SAP release, system size, upgrade method, data volume, infrastructure, customisations, and the activities included in the cutover.

The objective is not simply to estimate downtime but to understand which activities require the production system to be unavailable and which can be completed beforehand.

Downtime can be managed through:

• Detailed cutover planning
• Upgrade rehearsals
• Pre-production remediation
• Data preparation
• Transport sequencing
• Interface coordination
• Technical optimisation
• Cutover runbooks
• Business validation procedures
• Clearly defined contingency plans

A successful cutover should include technical validation as well as business confirmation that critical processes are operational before normal operations resume.

Custom code needs to be assessed against the target S/4HANA release before the upgrade.

Some developments may continue to work without changes. Others may require remediation because of changed APIs, deprecated functionality, data model changes, or new SAP architecture.

We recommend classifying custom developments into four categories:

• Retain - the development remains valid and compatible.

• Remediate - the development is still required but needs modification.

• Replace - standard SAP functionality provides a better alternative.

• Retire - the development is no longer needed.

This assessment is also an opportunity to adopt Clean Core principles and move appropriate extensions outside the S/4HANA core, including to SAP BTP where suitable.

An upgrade can affect integrations even when connected systems remain unchanged.

Changes to APIs, data structures, authentication, business processes, middleware, or SAP functionality can affect the way information moves between systems.

Integration testing should therefore cover critical end-to-end flows, such as:

• Orders and sales data
• Supplier and procurement data
• Invoices and payments
• Customer and vendor master data
• Inventory information
• Banking interfaces
• Warehouse and logistics systems
• CRM and e-commerce platforms
• External reporting and tax services

Testing should validate not only whether an interface technically runs, but whether the receiving system gets the correct data and the complete business process produces the expected result.

An upgrade generally means moving an existing SAP environment to a newer release while retaining the existing system and much of its configuration and data.

A migration or broader transformation can involve moving to a new S/4HANA environment, redesigning business processes, changing the data model, or selectively transferring historical data.

The right approach depends on the condition of the existing SAP landscape, the target architecture, business objectives, customisation level, data requirements, and desired degree of process transformation.

A readiness and impact assessment can help determine whether a technical upgrade, system conversion, selective transformation, or broader reimplementation is the most appropriate path.

Start with the current system rather than the desired go-live date.

A structured preparation phase should establish:

1. Current landscape - SAP release, infrastructure, integrations, add-ons, custom code, and key processes.
2. Target state - target S/4HANA release and required capabilities.
3. Upgrade impact - compatibility issues, simplification items, custom code, data, and interfaces.
4. Business requirements - critical processes, reporting, controls, and UK-specific requirements.
5. Testing strategy - technical, integration, regression, financial, and user acceptance testing.
6. Cutover strategy - downtime, responsibilities, sequencing, validation, and contingency procedures.
7. Post-go-live support - hypercare, issue management, monitoring, and optimisation.

This approach gives stakeholders a realistic view of the effort, risks, dependencies, and expected business impact before the upgrade enters execution.