| Thomas Ross Management Company Limited | Households | 2017 |
| Thompson Garden Care & Design Ltd | Administrative & support | 2025 |
| Thomson Software Solutions Limited | Information & communication | 1999 |
| THORPE2 Limited | Real estate | 2025 |
| Thoughts and Sparks Ltd | Professional & scientific | 2021 |
| Thoughtworks Consulting Limited | Information & communication | 2013 |
| THR Limited | Administrative & support | 2008 |
| Thrall Horde | Extraterritorial | 2012 |
| Three Keys of London Ltd. | Manufacturing | 2015 |
| Three Sixty Holdings Limited | Financial services | 2025 |
| Thrive Health and Fitness Ltd | Other services | 2025 |
| Thrive Health and Wellness (Collaborative) Limited | Health & social care | 2020 |
| Tibbett & Britten Consumer Group Limited | Transport & logistics | 1993 |
| Tidy Management Ltd | Professional & scientific | 2016 |
| Tiffany Cars Ltd | Wholesale & retail | 2026 |
| TIL Fire Security Systems Limited | Public administration | 2018 |
| Tilbury Roofing Ltd | Construction | 2025 |
| Tiller Garden Services Limited | Administrative & support | 2014 |
| Time IS Key Logistics Limited | Transport & logistics | 2025 |
| Tinashe Cyber Security Limited | Information & communication | 2018 |
| Tinies U.K. Limited | Education | 1993 |
| Tinkers Gifts Ltd | Construction | 2022 |
| Titan Construction & Developments Ltd | Construction | 2013 |
| Titan Roofing & Exteriors Ltd | Construction | 2025 |
| Titan Secure Limited | Wholesale & retail | 2025 |
| Tivan Group Limited | Information & communication | 2016 |
| TJ Home & Garden Ornaments Ltd | Manufacturing | 2022 |
| TJ Strategy and Consulting Ltd | Professional & scientific | 2019 |
| TJB Publishing Limited | Information & communication | 2024 |
| TJT Detailing Ltd | Administrative & support | 2023 |
| TM Decor Limited | Construction | 2017 |
| TM Tiling Limited | Construction | 2020 |
| TMA Engineering Services Ltd | Construction | 2026 |
| TN Publications Limited | Wholesale & retail | 2023 |
| TO ALL My Black Girls Ltd | Wholesale & retail | 2018 |
| TO YOU From ME Ltd | Wholesale & retail | 2024 |
| Togley Ltd | Wholesale & retail | 2018 |
| TOL Limited | Health & social care | 2015 |
| Tollgrade UK Limited | Information & communication | 2007 |
| Tology Limited | Construction | 2019 |
| Toms Home Improvements Limited | Construction | 2022 |
| Toni & ICC Bracknell Ltd | Administrative & support | 2025 |
| Toni-Marie Consulting Limited | Administrative & support | 2024 |
| Top Door Limited | Real estate | 2021 |
| Top Freight Ltd | Transport & logistics | 2024 |
| Top Girl Management Limited | Professional & scientific | 2023 |
| Top Notch Bespoke Fitted Furniture Limited | Construction | 2023 |
| Top Way Turismo Ltd | Administrative & support | 2018 |
| Topgas Consultancy Limited | Professional & scientific | 2023 |
| Topi Asset (UK) Limited | Information & communication | 2021 |
| Torink Cosmetics & Aesthetics Ltd | Administrative & support | 2016 |
| Torleven Heights Management Company Limited | Households | 2006 |
| Towelrads.Com Limited | Wholesale & retail | 2003 |
| Tower Leasing Limited | Administrative & support | 1988 |
| Tower Leasing South Limited | Administrative & support | 2021 |
| Towncourt Homes (Highmoor) LLP | | 2019 |
| Towncourt Homes (MG) LLP | | 2024 |
| Towncourt Homes (Penn) LLP | | 2021 |
| Towncourt Homes (Poole) LLP | | 2021 |
| Towncourt Homes Limited | Construction | 2001 |
| Townsend Lighting and Electrical Services Limited | Construction | 2009 |
| Tqa-Os Ltd | Information & communication | 2025 |
| Trac Property Holdings Limited | Real estate | 2018 |
| Tracks Laser & Electronics Ltd | Manufacturing | 1994 |
| Trademark Transport Limited | Transport & logistics | 2021 |
| Tradies Enterprise Ltd | Wholesale & retail | 2026 |
| Trading Leisure Ltd | Extraterritorial | 2023 |
| Trading Stack Limited | Information & communication | 2024 |
| Traidy Ltd | Information & communication | 2025 |
| Train Body Smart Ltd | Other services | 2023 |
| Training Evolution Ltd. | Education | 2023 |
| Trans Serv Transport and Labour Service Ltd | Transport & logistics | 2015 |
| Transco Express (LHR) Limited | Transport & logistics | 2010 |
| Trattoria DI Lorenzo Ltd | Hospitality | 2023 |
| Travel Nanda Ltd | Administrative & support | 2020 |
| Treetops Horse Box Hire Ltd | Administrative & support | 2022 |
| Treetops Storage Centre Limited | Transport & logistics | 2019 |
| Tremayne Distributions Limited | Transport & logistics | 2009 |
| Trend Control Systems Limited | Manufacturing | 1982 |
| Trent and Sons Limited | Construction | 2022 |
| Trickshot Digital Ltd | Professional & scientific | 2022 |
| Trinity Integrated Systems Limited | Information & communication | 1998 |
| Trinity Link Ltd | Transport & logistics | 2025 |
| Trinity Place (Bracknell) Management Limited | Households | 2018 |
| Triple Eight MOT Ltd | Wholesale & retail | 2024 |
| Triple One Management Company Limited | Households | 2004 |
| Triplot Ltd | Manufacturing | 2026 |
| Tripple Seven Games Ltd | Information & communication | 2025 |
| Tristonia Ltd | Information & communication | 2026 |
| Triveni Venkatraman Ltd | Health & social care | 2018 |
| Trivolt Services Limited | Construction | 2026 |
| TRS Engineering Solutions Ltd | Manufacturing | 2016 |
| True Vision Homes Limited | Construction | 2026 |
| Truecare Group Limited | Extraterritorial | 1998 |
| Truecare Holdings Limited | Extraterritorial | 2004 |
| Truevolt Ltd | Construction | 2026 |
| Truu Lusso Ltd | Administrative & support | 2024 |
| TS & SK Ltd | Real estate | 2022 |
| TS Lighting Services Limited | Professional & scientific | 2024 |
| TSF2 Limited | Other services | 2021 |