CoCounsel
Thomson Reuters' AI assistant, drawing on Practical Law and Westlaw. Sold in the UK as CoCounsel Legal UK; no published price.
Overview
CoCounsel is Thomson Reuters' AI assistant for lawyers. It began as a Casetext product, which Thomson Reuters bought in 2023, and is now sold as part of Thomson Reuters' legal research services. It answers research questions, reviews and summarises documents, and drafts, drawing on Practical Law guidance, Westlaw primary law and the firm's own material.
For solicitors in England and Wales
Thomson Reuters launched CoCounsel Legal in the UK in January 2026, with Deep Research across Westlaw and Practical Law (Thomson Reuters, January 2026). A lighter product, CoCounsel Essentials UK, is also sold.
The next generation of CoCounsel Legal launched in the US in August 2026. Thomson Reuters says UK availability is expected later this year, so the UK and US products may differ for now (Thomson Reuters, August 2026).
Thomson Reuters describes a mix of models from Anthropic, OpenAI and Google alongside its own, and says the new CoCounsel Legal is built on Anthropic's Claude Agent SDK.
Pricing
Checked 29 September 2026. Thomson Reuters publishes no UK price for CoCounsel. Its UK product page offers a free demo and a sales contact.
Security and data
Checked 29 September 2026 against Thomson Reuters' own pages.
- Training. Thomson Reuters says it does not use user content or prompts to train CoCounsel or any third-party model, and that OpenAI and Google are contractually prohibited from training on customer data (CoCounsel Essentials UK FAQ).
- Where data is held. Hosting and processing are in the US; region-based hosting is available in the UK, Australia and Canada (same FAQ). Ask for UK hosting if the firm needs it.
- Certifications. An ISO/IEC 27001:2022 certificate issued to Thomson Reuters (Professional) UK Ltd lists CoCounsel in scope (Trust Center). Thomson Reuters also states SOC 2 and ISO 42001 for CoCounsel Legal (CoCounsel Legal).
Using it safely
- CoCounsel's sources are better than a general assistant's, but its answers still need checking. See the Stanford study noted on the Westlaw UK page. Paragraph 3.2 of the SRA Code of Conduct for Solicitors requires a competent service.
- Confirm with Thomson Reuters where the firm's account is hosted before uploading client documents.