Claude in Microsoft 365 Copilot: How to Enable It (UK Guide)

TL;DR: Claude Sonnet 4.6 and Claude Opus 4.6 are selectable inside Microsoft 365 Copilot's Researcher agent and Copilot Studio. UK tenants must opt in, an admin enables Anthropic under Copilot → Settings → Data access in the M365 admin centre. The catch: your data leaves the EU Data Boundary when routed to Claude, so update your DPIA first. Worth enabling for most SMEs; regulated businesses should check with their compliance lead before flipping the switch.

Claude has been available inside Microsoft 365 Copilot since late 2025. Anthropic's models, Claude Sonnet 4.6 and Claude Opus 4.6, now sit alongside OpenAI's models inside Microsoft's productivity suite, and UK adoption is picking up as admins work through the opt-in process. For UK businesses, the situation is a bit more nuanced than the marketing implies.

If you're weighing up whether to enable it, what it actually changes, or what compliance traps to know about before flipping the switch, this is the practical guide we wish we'd had when clients first started asking.

What's Actually Happening Here?

Microsoft has been quietly building model choice into Copilot. Until late 2025, asking Copilot a question meant asking OpenAI's GPT family with extra Microsoft scaffolding around it. Since January 2026, Anthropic has been an official subprocessor for Microsoft 365 Copilot, meaning admins can route certain Copilot features through Claude instead.

Where Claude actually appears in Copilot today:

• Researcher agent: Copilot's deep-research feature can now use Claude Opus 4.6 instead of OpenAI's reasoning models
• Copilot Studio: When building custom agents for your business, Claude Sonnet 4.6 and Opus 4.6 are now selectable as the underlying model
• Agent Mode in Excel and Word: Claude can power complex multi-step tasks inside Office apps

Importantly, Claude is *not* the default model for the standard Copilot chat experience. Users have to actively select it (via a 'Try Claude' button in the Researcher interface) once an admin has enabled the integration.

Standalone Claude vs Claude in Copilot: The Key Differences

This is the bit most articles skip, and it matters more than the marketing suggests.

The key insight: Claude *in* Copilot is not the same product as Claude on its own. Microsoft mediates the relationship, you're getting Anthropic's intelligence applied to Microsoft's data and workflow plumbing.

If you mostly need Claude to summarise a long document outside of work systems, the standalone product is still a stronger fit. If you want Claude reasoning over your actual emails, SharePoint files, and Teams chats, the Copilot integration is what you're after.

How to Enable Claude in Microsoft 365 Copilot

There are two layers: admin and user.

Step 1: Admin Enablement

For UK customers, Anthropic models are off by default. (For most non-UK, non-EU customers, they're on by default. UK and EU/EFTA tenants have to opt in deliberately, Microsoft made this distinction to give regulated regions room to assess the change first.) An admin with the right Microsoft 365 role needs to:

1. Sign in to the Microsoft 365 admin centre
2. Navigate to Copilot → Settings → Data access
3. Find AI providers operating as Microsoft subprocessor
4. Toggle Anthropic to enabled
5. Confirm the change (this acknowledges that Anthropic now processes your data as a Microsoft subprocessor)

The change typically applies tenant-wide within a few hours. There's no per-user rollout option, it's all-or-nothing for the organisation.

Step 2: User Activation

Once admin enablement is in place:

1. Sign in to the Microsoft 365 Copilot app (web, desktop, or mobile)
2. Open Chat and select Researcher under Agents
3. Look for the Try Claude button in the interface
4. Click it to switch the Researcher agent's underlying model to Claude

For Copilot Studio, model selection happens during agent creation, when building or editing an agent, Claude Sonnet 4.6 and Opus 4.6 will appear in the model dropdown alongside OpenAI's options.

There's no extra licensing cost. If your users have a Microsoft 365 Copilot licence, Claude access is included.

The Pros: When Claude Wins Inside Copilot

Three things make Claude genuinely useful in this context:

Better long-document reasoning. Claude has historically been stronger than GPT models at synthesising long, complex documents: contracts, technical specifications, multi-source research. If your team uses Researcher to pull together briefings or reports from multiple sources, Claude often produces tighter, more accurate output.

Different writing voice. GPT and Claude have measurably different default styles. Claude tends to be more cautious, more structured, and less prone to generic 'AI-flavoured' writing. For client-facing drafts, executive summaries, or anything where tone matters, having a second voice to compare against is genuinely valuable.

Stronger handling of nuance. On tasks requiring careful judgment, interpreting policy, assessing risk, navigating ambiguity, Claude Opus 4.6 tends to outperform on the kind of work where you'd want to review the output carefully before sharing it.

The practical recommendation: use Sonnet 4.6 as the default for everyday queries (it's faster), and switch to Opus 4.6 when the task is high-stakes or genuinely complex. It's a bit like having two heroes on call: Sonnet's the everyday workhorse, Opus is the one you call in for the big jobs.

The Cons and Risks: What to Know Before You Enable

This is where UK businesses need to pay particular attention.

1. Data Leaves the Microsoft Boundary

When Copilot routes a query to Claude, your data, including the document context, email content, or files Copilot has grounded the query in, is sent to Anthropic's infrastructure. Anthropic hosts this on AWS or Google Cloud datacentres, primarily in the United States.

For most Microsoft services, customers can rely on Microsoft's EU Data Boundary commitments to keep data within the EU. Anthropic models are explicitly excluded from this commitment.

For UK and EU businesses subject to GDPR, this matters. You're not breaking the law by enabling it (Microsoft has a Data Processing Addendum (DPA) covering Anthropic as a subprocessor, and Anthropic doesn't train on customer data) but you do need to:

• Update your privacy notices and Data Protection Impact Assessment (DPIA) records
• Inform your data protection officer (or whoever holds that responsibility)
• Consider whether your client contracts allow for new subprocessors of this kind

If you're a regulated business (legal, healthcare, financial services) talk to your compliance lead before enabling.

2. No In-Country Processing Guarantees

Where Microsoft's standard Copilot service offers in-country processing for certain regulated customers, those guarantees do not extend to Anthropic-routed queries. If your contracts or sector regulations require UK-only data processing, Claude in Copilot is probably not for you.

3. Subprocessor Status Isn't Universally Enough

Some clients, particularly larger enterprises and public sector bodies, have approved supplier lists that don't include Anthropic, or contractual restrictions on what subprocessors can be added without notification. If you have client agreements with strict data processing terms, check before flipping the switch.

4. The Opt-Out Visibility Problem

Once you enable Anthropic, individual users can choose Claude in Researcher or build agents that use Claude in Copilot Studio. There's no fine-grained way to say 'only the marketing team can use Claude', it's tenant-wide. If you only want certain teams to use it, you'll need internal policy rather than technical controls.

Tips for Getting the Most Out of Claude in Copilot

A few practical things we've learned from clients who've adopted it:

Start with Researcher, not Chat. Standard Copilot chat queries don't (yet) use Claude. The Researcher agent is where you'll see the biggest difference. Use it for genuine research tasks: competitive analysis, summarising long policy documents, building briefings from multiple internal sources.

Pick the right model for the task. Sonnet 4.6 is faster and handles 80% of work well. Opus 4.6 is slower but noticeably better at deep reasoning. Treat them like different tools, not different brands.

Always validate the output. This applies to any AI tool, but it's especially important when Copilot is grounding answers in your actual business data. A confidently wrong answer about your own pricing or contract terms can be worse than no answer at all.

Compare against the default model. On any meaningful task, run the prompt through both Claude and the OpenAI default. The differences are real and will tell you which model your team should default to for which kinds of work.

Treat agent design seriously. If you're building Copilot Studio agents on Claude, spend time on the system prompt and the grounding sources. The model is only as good as the context it's given.

Don't replace human review. For client-facing or compliance-sensitive output, treat Claude as a starting draft, not a finished product.

Should Your Business Enable It?

Our honest take, based on what we see across our client base:

Enable it if:

• You're a small or medium business in the UK that isn't subject to strict in-country data processing requirements
• Your team uses Microsoft 365 Copilot regularly and would benefit from a second model option for harder tasks
• You're comfortable with the additional subprocessor disclosure in your privacy documentation
• You have someone (internal or your IT provider) who can update the DPIA and inform staff

Hold off if:

• You're a regulated business (legal, healthcare, financial services) without first running it past your compliance lead
• Your contracts with clients or suppliers restrict approved subprocessors
• You're working on a defence or government contract with strict data residency rules
• You haven't yet got the basics right (MFA, Conditional Access, proper Microsoft 365 Business licensing) because Copilot decisions sit on top of those foundations, not instead of them

For most of the businesses we support across Shropshire, Herefordshire and the West Midlands, the answer is 'yes, but with eyes open.' Update the paperwork, brief your team, and turn it on.

A Note on the Wider AI Picture

Microsoft adding Anthropic to Copilot is a significant shift, it's the first time a major productivity suite has officially offered a competitor's frontier model alongside its own. We expect this trend to continue, with model choice becoming the norm rather than the exception across enterprise AI tools.

That makes governance even more important. Knowing which models your business uses, what data they process, and which subprocessors are involved is no longer an edge case, it's table stakes for any business using AI at work. If you don't have an AI acceptable use policy yet, now's a sensible time to draft one.

If you'd like help with any of this, enabling Claude properly, updating your DPIA, building Copilot Studio agents that actually deliver value, or just getting your Microsoft 365 setup ready for Copilot in the first place, get in touch. It's the kind of work we do every day for businesses across the region.