Microsoft to default UK Copilot tenants to Claude on Dec. 9, 2026

On Dec. 9, 2026, Microsoft will enable Anthropic’s Claude models by default for UK Microsoft 365 Copilot tenants with no existing Anthropic selection. The company set the date in message center post MC1546435, published Nov. 10, and administrators can opt out before it takes effect.

Until now, Microsoft has treated UK tenants like those in the EU and EFTA for this setting: Claude stays off by default in all three regions. Most other commercial tenants already have Claude on by default, so the December change brings the UK closer to Microsoft’s wider commercial pattern.

What changes on Dec. 9?

The automatic switch applies only to UK tenants that have not selected Anthropic under the admin center setting “AI providers operating as Microsoft subprocessors.” It does not replace a provider choice that a tenant has already made.

Existing selections remain in place:

• “All users” enables Claude for every tenant user.
• “No users” keeps Claude disabled for the tenant.
• Specific users and groups retain their selected access.

Microsoft added the “Copilot in Microsoft 365 apps only” option on April 3. It let European and UK tenants use Claude only within Word, Excel and PowerPoint, rather than across other Copilot experiences. Microsoft will retire that option and move affected tenants to “All users” on Dec. 9.

In plain terms: Dec. 9 makes Claude the UK default, while the setting still gives administrators control over each tenant.

Which controls remain with administrators?

Administrators with either the AI Administrator or Global Administrator role can opt out through Copilot > Settings > View all > AI providers operating as Microsoft subprocessors > Anthropic. The change therefore preserves tenant-level governance even as Microsoft raises the default level of access.

The preserved group option gives tenants a middle path between tenant-wide deployment and a complete opt-out. Microsoft does not remove that granularity, although it raises access for tenants that recorded no preference.

In plain terms: administrators can preserve Claude’s off state, but they must act before Dec. 9 to do so.

Where does the data go?

Anthropic acts as a Microsoft subprocessor, so Microsoft’s Product Terms and Data Protection Addendum apply to that relationship. The documentation nevertheless places Claude outside several regional processing commitments.

• Claude in Copilot, Researcher, Copilot Studio, Power Platform and the Microsoft 365 apps is excluded from the EU Data Boundary and, where applicable, in-country processing commitments.
• Separately governed “Anthropic models with Data Retention,” including Claude Fable 5, stay off until an administrator opts in.

The Register reported, citing Microsoft’s documentation, that Anthropic processes the relevant data in the United States. Because the UK already sits outside the EU Data Boundary, the practical issue for local administrators is the U.S. processing location and the exclusion from applicable in-country commitments. They must decide whether that arrangement meets their own data-handling rules.

In plain terms: access expands, but UK data protection does not expand with it.

Why does the EU plan not cover the UK?

On Nov. 5, Microsoft said Claude processing for EU and EFTA customers will move inside the EU Data Boundary by the end of 2026. The company also said the setting would remain off by default in those regions.

The end-2026 statement is a roadmap, not a description of current coverage. That announcement did not mention the UK, which sits outside the boundary, and it provides no current UK processing commitment.

In plain terms: Microsoft has promised EU data-boundary coverage on a separate timetable, but its announcement leaves the UK without a stated end-2026 deadline.

The immediate competitive variable is administrative acceptance of Anthropic’s US processing terms. Decisions before Dec. 9 will shape whether Claude becomes routine across the UK market or remains a contested Copilot choice, even as most other commercial tenants already have it on by default.