Microsoft 365 Copilot Now Defaults to Anthropic Claude — But Your UK Tenant Is Off by Default. The 12 May 2026 Opt-In Decision Every UK Business Needs to Make
On 4 May 2026 Microsoft's notice MC1269241 took effect and Anthropic Claude became the default Copilot model in Excel and PowerPoint — with Word following in summer 2026. But there is a twist for UK businesses: your tenant is set to OFF by default, the data processing happens outside the EU Data Boundary, and a Global Administrator has to opt in explicitly. Here is the full decode — what changed, what the EU Data Boundary exit means for GDPR and Cyber Essentials v3.3, the realistic cost of getting the governance wrong, and the 10-step opt-in decision framework for UK SMEs running Microsoft 365 Copilot today.
