| Thermo Fisher Scientific Odyssey Holdings Limited | Professional & scientific | 2012 |
| Thermo Fisher Scientific One Limited | Extraterritorial | 2018 |
| Thermo Fisher Scientific PNM Limited Liability Partnership | | 2018 |
| Thermo Fisher Scientific Powder UK Holdings Limited | Extraterritorial | 2021 |
| Thermo Fisher Scientific Powder UK Senior Holdings Limited | Extraterritorial | 2023 |
| Thermo Fisher Scientific Powder US Holdings Limited | Extraterritorial | 2021 |
| Thermo Fisher Scientific Powder US Limited | Extraterritorial | 2024 |
| Thermo Fisher Scientific PPD Development Holdings Limited | Extraterritorial | 2024 |
| Thermo Fisher Scientific PR Limited | Extraterritorial | 2025 |
| Thermo Fisher Scientific UK Holding Company Financing Limited | Extraterritorial | 2021 |
| Thermo Onix Limited | Manufacturing | 1996 |
| Thermo Optek Limited | Professional & scientific | 1991 |
| Thermo TLH (UK) Limited | Professional & scientific | 2001 |
| Thermocill Ltd | Construction | 2020 |
| Thestudios (West Brom) Limited | Real estate | 2023 |
| Theta Technical Consultancy Limited | Administrative & support | 2012 |
| Theukbroker.Com (Online) Ltd | Administrative & support | 2017 |
| THG 100 King Street Limited | Financial services | 2020 |
| THG Beauty I2 Limited | Financial services | 2025 |
| THG Beauty Limited | Financial services | 2021 |
| THG Eco Limited | Financial services | 2021 |
| THG Experience Limited | Financial services | 2021 |
| THG Hangar 2 Limited | Financial services | 2020 |
| THG Hangar Holdco Limited | Financial services | 2020 |
| THG Hosting Limited | Information & communication | 1998 |
| THG Icon CP Propco Limited | Financial services | 2020 |
| THG Ingenuity Limited | Financial services | 2021 |
| THG Intermediate Holdings Limited | Extraterritorial | 2020 |
| THG Intermediate Opco Limited | Financial services | 2019 |
| THG International Limited | Extraterritorial | 2016 |
| THG Luxury Limited | Financial services | 2021 |
| THG Nutrition Limited | Financial services | 2021 |
| THG Nutrition OM Limited | Financial services | 2025 |
| THG Ondemand Limited | Financial services | 2021 |
| THG Operations Holdings Limited | Financial services | 2019 |
| THG PLC | Wholesale & retail | 2008 |
| THG Shared Services Limited | Financial services | 2021 |
| THG Shelfco Limited | Financial services | 2021 |
| THG Studios Limited | Administrative & support | 2007 |
| THG Trustee Limited | Extraterritorial | 2016 |
| Thia Technologies Limited | Information & communication | 2024 |
| Thin Grey Line Limited | Professional & scientific | 2023 |
| Think Link Lead Limited | Administrative & support | 2023 |
| Thios Labs UK Limited | Professional & scientific | 2024 |
| Third Dimension AI Limited | Information & communication | 2024 |
| Third Mynd Ltd | Professional & scientific | 2015 |
| Thirlcrest Limited | Extraterritorial | 1979 |
| This IS Project YOU Ltd | Health & social care | 2021 |
| Thisa Psps Limited | Information & communication | 2021 |
| Thisthat&Others Limited | Manufacturing | 2022 |
| Thistle Bidco Limited | Professional & scientific | 2021 |
| Thistle Finco 1 Limited | Financial services | 2024 |
| Thistle Finco 2 Limited | Financial services | 2024 |
| Thistle Holdco Limited | Professional & scientific | 2021 |
| Thistlecrown Limited | Real estate | 2024 |
| THL Medico Limited | Health & social care | 2011 |
| Thompson Recycling LLP | | 2014 |
| Thompson Visinoni LLP | | 2014 |
| Thompsons Recycling Ltd | Water & waste | 2014 |
| Thorley Day Nursery Limited | Health & social care | 2008 |
| Thorn Bank Lodge Residents Company Limited | Households | 2000 |
| Thorndale Court (Timperley) Limited | Households | 1976 |
| Thorsen Properties Limited | Real estate | 2025 |
| Thorup Limited | Professional & scientific | 2024 |
| THR11VE Ltd | Professional & scientific | 2025 |
| Three Counties Reclamation Limited | Water & waste | 1999 |
| Three Figs Creative Limited | Administrative & support | 2025 |
| Three Oaks Property Management Ltd | Households | 2018 |
| Three Successors Ltd | Wholesale & retail | 2023 |
| Three Sycamores Financial Consulting Limited | Professional & scientific | 2024 |
| Thrive Consultancy Services Limited | Professional & scientific | 2022 |
| Thrive Wealth Management Limited | Professional & scientific | 2016 |
| Thrive Wild Ltd | Education | 2026 |
| Thryver Ltd | Wholesale & retail | 2025 |
| Thunder Holdco UK Ltd | Financial services | 2024 |
| Thunderhead (One) Ltd. | Information & communication | 2012 |
| Thunderhead Midco (One) Limited | Information & communication | 2015 |
| Tiamat Investments Limited | Financial services | 2026 |
| Ticketure UK Limited | Financial services | 2025 |
| Tidal Tents Ltd | Administrative & support | 2024 |
| Tier One IT Services Limited | Information & communication | 2018 |
| Tifo Group Limited | Financial services | 2016 |
| Tifo Limited | Information & communication | 2016 |
| Tiger 1 Legal Services Limited | Professional & scientific | 2021 |
| Tiger Capital Finance Limited | Financial services | 2026 |
| Tiger Ventures Limited | Professional & scientific | 2023 |
| Tigers & Foxes Limited | Professional & scientific | 2025 |
| TIL Mechanical Services Ltd | Manufacturing | 2018 |
| Tilda Property Trading Ltd | Real estate | 2026 |
| Tile by Tile Ltd. | Wholesale & retail | 2016 |
| Tiles and Smiles Limited | Construction | 2019 |
| Tilhill Forestry Limited | Agriculture & fishing | 1996 |
| Tili Associates Limited | Real estate | 2018 |
| Tillard Avenue (Cheadle Heath) Maintenance Co. Limited | Households | 1980 |
| Tilly's Coffee Ltd | Hospitality | 2017 |
| TIM Coles Consulting Limited | Professional & scientific | 2021 |
| Timash Engineering Limited | Professional & scientific | 2024 |
| Timberlake BTL Ltd | Real estate | 2023 |
| Time IS a Thief Ltd. | Information & communication | 2017 |
| Timeband Limited | Real estate | 1988 |