Microsoft will turn on Anthropic’s Claude AI models by default for UK Copilot customers from 9 December, The Register reported. Anthropic, acting as a Microsoft subprocessor, will process customer data in the US. UK organisations that do not select a setting by the deadline will have Claude enabled, though administrators can still opt out. Claude is already the default for most Microsoft commercial customers, but the EU, EFTA and UK had been exceptions until now.
Microsoft’s Copilot documentation states that Claude models fall outside the EU Data Boundary and are not covered by in-country processing commitments. This means UK customer data will be handled under US jurisdiction, which may raise compliance concerns for banks, insurers and healthcare providers. Some advanced Anthropic models, such as Claude Fable 5 and Claude Mythos 5, remain off by default everywhere, and require explicit opt-in.
The move comes as the Institute for Public Policy Research (IPPR) warns about the UK public sector’s reliance on US technology. Only 15.4% of spending with top tech suppliers stays with British-owned companies, while the US receives the largest share. IPPR urges the government to act as a single buyer and improve supplier flexibility.
UK administrators must confirm their Copilot settings by 9 December to avoid defaulting to Claude. The shift may prompt further scrutiny of cross-border data flows and supplier concentration in regulated industries.
