From acquisition to alignment: how accountancy firms should integrate IT properly
Growth through acquisition is no longer the ‘new’ way to do things in the UK accountancy market – it’s fast becoming the norm. Whether it’s driven by succession planning, a strategic expansion or private equity investment, more firms are joining forces than ever before.
While the commercial side of the deal usually moves at pace, the technical side is often where things either click into place… or start to unravel.
If you’re leading the IT team, this is your moment. Get the integration right, and you’ve built a powerful, secure platform for the firm’s future. Get it wrong (or rush it), and you’re looking at months of frustration, security gaps, and technical debt.
So, how do you make sure your integration is a success?
Start with proper discovery
The biggest mistake we see is assuming that ‘same’ means ‘simple’. It’s tempting to think: ‘They’re on Microsoft 365, we’re on Microsoft 365 – how hard can it be?’
In reality, no two environments are the same. Before you start moving data, you need to understand four key areas.
FREE Audit
Stripping away the digital debt
Our free license audit is all about finding the hidden wins. We’ll help you tidy up your spend and make sure you aren’t paying for tools you never touch. At the same time, we’ll ensure you have the ‘security muscle’ needed for a modern, AI-integrated office. It’s about cutting any excess so you can put that budget toward real innovation.
Active directory and on-premises identity
Identity is the foundation of everything, but it’s rarely straightforward. You need to document every Windows Server AD domain in the mix.
Ask the awkward questions now: Are there trust relationships in place? How is the synchronisation actually handled?
If you don’t uncover any glitches now, they’ll definitely find you later – at a really inconvenient time.
Microsoft 365 tenant visibility
You need a crystal-clear map of what’s inside each tenant. This isn’t just a head-count of users – it’s about understanding the environment:
- Number of users
- SharePoint site count and data size
- How Teams is being used
- OneDrive storage volumes
- Workloads in use
- Compliance and retention settings
- Intune and device management
This is where the details matter. Some workloads move over easily. Others, like Microsoft Dynamics, can cause headaches and will likely heavily dictate your strategy.
Application dependencies
Accountancy firms live and breathe their software – from practice management platforms to CRM tools and specialist tax tools.
You need to map out which apps rely on which identity. Which applications depend on on-premises identity? Which are integrated with Microsoft 365 and Entra ID? Which ones use SSO? Which ones are already sitting in your main tenant?
Mapping these links early is the only way to avoid disruption later, particularly when user accounts or domain structures change.
Migration tooling
Don’t assume your tools can handle everything. While moving Exchange and SharePoint is usually straightforward, things like Planner, Forms, Power BI or Power Automate can be much trickier. Knowing the limits of your tools now saves you from a nasty surprise halfway through the project.
Choosing your tenant consolidation strategy
In most mergers, the goal is simple: get everyone working together as fast as possible. Usually, that means moving everyone into a single tenant.
Between managing sensitive client data and maintaining email continuity, there is a lot of pressure to get this right. The National Cyber Security Centre often points out that periods of big change are when security is most at risk.
Deciding which tenant becomes the ‘home’ isn’t always a simple choice.
Choosing your tenant consolidation strategy
In most mergers, the goal is simple: get everyone working together as fast as possible. Usually, that means moving everyone into a single tenant.
Between managing sensitive client data and maintaining email continuity, there is a lot of pressure to get this right. The National Cyber Security Centre often points out that periods of big change are when security is most at risk.
Deciding which tenant becomes the ‘home’ isn’t always a simple choice.
Here are the factors worth weighing up carefully:
The technical heavy lifters: If one firm has a complex Dynamics setup, it might be easier to move everyone else to them.
The future brand: If the new firm is taking one specific name, it often makes sense to consolidate into that tenant.
Size and scale: Moving the smaller firm into the larger one is common, but it’s not a hard-and-fast rule.
It’s easy to view tenant consolidation as a technical project. In reality, it directly affects people and clients. Integration is an opportunity to strengthen your controls and service, not dilute them.
Plan for day 1 and day 100
For day 1, focus on the essentials:
- Stable identity and authentication
- Reliable email flow
- Secure access to collaboration tools
- Clear security baselines
Then start to look at the bigger picture:
- Full tenant consolidation
- SharePoint and Teams rationalisation
- Device re-enrolment
- Application alignment
- Policy standardisation
- Domain migration or decommissioning
You don’t have to fix everything on the first morning. You just need a solid roadmap.
The biggest risk? ‘Temporary’ workarounds that quietly become permanent. Running parallel environments forever is expensive, messy, and a security risk you just don’t need.
Treat integration as a strategic move
If your firm is on a growth path, you shouldn’t be reinventing the wheel every time you acquire a new practice.
IT needs a seat at the table while the deal is still being discussed, not just once the contracts are signed. When you have early visibility into the tech stack you’re inheriting, you can give realistic costs and timelines from the start.
Over time, developing a repeatable integration framework becomes a competitive advantage. You’ll be the firm that can scale quickly and confidently, knowing your technology is ready for whatever comes next.
At Kascade, we help UK accountancy firms make sense of Microsoft 365 tenant consolidation, technical due diligence, and the heavy lifting of post-acquisition integration. Our goal is always the same: to strip away the disruption and protect your security, leaving you with a clean, scalable platform that actually supports your growth rather than getting in the way of it.
Ready to move from reactive to strategic?
Let’s talk through your roadmap to make sure your IT integration is an asset, not a bottleneck.
