| System Works Limited | Information & communication | 1997 |
| Systems Complete Limited | Information & communication | 1980 |
| T & M Motors Limited | Manufacturing | 1999 |
| T & M Properties Limited | Real estate | 1999 |
| T B C Contracts Limited | Construction | 2006 |
| T R Smith & SON Limited | Construction | 2007 |
| Tacct Limited | Education | 2004 |
| Tackle Sales Limited | Extraterritorial | 1995 |
| Tand Properties Limited | Real estate | 2026 |
| Tanya Properties Ltd | Real estate | 2016 |
| Tariq 99 Mart Limited | Wholesale & retail | 2025 |
| Tassein Limited | Information & communication | 1995 |
| Tastes Ltd | Wholesale & retail | 2006 |
| Taxaway Holdings Limited | Professional & scientific | 2017 |
| Taylor & Johnson Limited | Extraterritorial | 1994 |
| TBC Developments (Kingsclere) Limited | Construction | 2004 |
| TC Eventing Limited | Other services | 2016 |
| Tcker Limited | Information & communication | 2022 |
| Tdata Services Limited | Information & communication | 2006 |
| Teamwork IMS Limited | Professional & scientific | 2007 |
| Tech-A Limited | Professional & scientific | 2000 |
| Technestdigitals Ltd | Wholesale & retail | 2025 |
| Tendereyes Software Ltd | Professional & scientific | 2006 |
| Tephi Design Limited | Wholesale & retail | 2007 |
| Test Valley Paving Ltd | Construction | 2006 |
| Tetra Tech International Development Europe Limited | Professional & scientific | 2000 |
| Tetra Tech International Development Limited | Professional & scientific | 1999 |
| Tevfik Limited | Real estate | 2004 |
| TFS Payroll Solutions Limited | Professional & scientific | 1996 |
| Thames Carp Tours Limited | Agriculture & fishing | 2006 |
| Thames Fleet Purchasing Limited | Administrative & support | 1998 |
| Thames Valley Archaeological Services Limited | Professional & scientific | 1999 |
| Thames Valley Buses Limited | Transport & logistics | 1973 |
| Thames Valley Cleaning Limited | Administrative & support | 1971 |
| Thames Valley Specialist Products Limited | Wholesale & retail | 1999 |
| Thatcham Cars Limited | Information & communication | 2005 |
| Thatcham Registrars Limited | Administrative & support | 2001 |
| Thatcham Research | Professional & scientific | 1969 |
| THE 129 Management Company Limited | Households | 1992 |
| THE 5 Rivers Property Company Limited | Real estate | 2004 |
| THE 73 Frances Road (Management Company) Limited | Administrative & support | 1995 |
| THE Abbey School, Reading | Education | 1914 |
| THE Ability Organisation Limited | Wholesale & retail | 1998 |
| THE Biryani Mama Ltd | Hospitality | 2021 |
| THE Bradfield Foundation | Professional & scientific | 1990 |
| THE Butt Karahi Ltd | Hospitality | 2024 |
| THE Caister (Wokingham) Management Company Limited | Households | 2004 |
| THE Churchill (8F) Locomotive Company Limited | Transport & logistics | 1990 |
| THE Communicare Trust (Reading) | Health & social care | 1999 |
| THE Crofton Optical Group Limited | Extraterritorial | 1969 |
| THE Development Business Limited | Professional & scientific | 2007 |
| THE Fulham Grocery Company Limited | Wholesale & retail | 2006 |
| THE Good Cook Company (Hungerford) Limited | Hospitality | 2006 |
| THE Hambridge Lane (Newbury) Management Limited | Real estate | 1989 |
| THE Institute of Marketing (Pre-Charter) | Extraterritorial | 1921 |
| THE John Neill Limited Partnership | | 2024 |
| THE KAY Management Group Limited | Professional & scientific | 1987 |
| THE Kendrick Trust | Education | 1998 |
| THE Knowledge, Skills and Experience Foundation | Information & communication | 2017 |
| THE Landmark Trust (Auchinleck) Limited | Arts & recreation | 1998 |
| THE Landmark Trustee Company Limited | Arts & recreation | 1989 |
| THE Lawn Company Limited | Administrative & support | 1998 |
| THE Lundy Company Limited | Hospitality | 1969 |
| THE Memory Maps Company Ltd | Professional & scientific | 1997 |
| THE Mobile Shelving Company Limited | Manufacturing | 2008 |
| THE Old School Yard Management Company Limited | Hospitality | 1996 |
| THE Oratory Schools Association | Education | 1931 |
| THE Poplars (Didcot) Management Company Limited | Households | 1991 |
| THE Purple Turtle Limited | Hospitality | 1996 |
| THE Racecourse Association Limited | Other services | 1907 |
| THE Reading Van Centre Limited | Professional & scientific | 1997 |
| THE Sash Window Workshop Trading Limited | Manufacturing | 1994 |
| THE Skincare Sanctuary Limited | Wholesale & retail | 1997 |
| THE Specialist Roofing Company (London) Limited | Construction | 2014 |
| THE Ufton Court Educational Trust | Education | 2006 |
| THE Venue Book Limited | Transport & logistics | 1990 |
| THE Warfield Word Limited | Information & communication | 2006 |
| THE Wellington College Limited | Education | 2007 |
| THE Wright Consultancy Limited | Administrative & support | 2007 |
| THE X-Fliers Limited | Arts & recreation | 1997 |
| Thrasos Limited | Information & communication | 2011 |
| Tickitape Limited | Professional & scientific | 1984 |
| Time Mirror Ltd | Other services | 2006 |
| TJA Consulting Ltd | Professional & scientific | 2006 |
| TLG Accounting Limited | Information & communication | 2007 |
| TLS Lettings & Estate Agents Limited | Real estate | 2004 |
| TO Freight Ltd | Transport & logistics | 2024 |
| Toad Hall Nursery Limited | Other services | 1997 |
| Tollbridge Ltd. | Real estate | 1966 |
| Tomodomo Network Limited | Information & communication | 2001 |
| Tony Weal Limited | Construction | 2007 |
| Toolzoo.Co.Uk Limited | Extraterritorial | 1978 |
| Top Quality Properties Limited | Construction | 1997 |
| TPA Studio Limited | Professional & scientific | 2004 |
| TPL Marketing Limited | Extraterritorial | 1992 |
| Trackelite Limited | Professional & scientific | 2001 |
| Tradewolf Ltd | Wholesale & retail | 2025 |
| Traffic Management Consultants Limited | Construction | 1995 |
| Transaxis Consulting Limited | Professional & scientific | 2011 |
| Transcendence Coaching Limited | Professional & scientific | 2018 |