| Tomad Limited | Professional & scientific | 2019 |
| Tomasz Opoka Ltd | Transport & logistics | 2018 |
| Tomdanny Ltd | Health & social care | 2019 |
| Tomfab Limited | Other services | 2012 |
| Tomjan Ltd | Transport & logistics | 2017 |
| Tomkowscy International Transport Ltd | Transport & logistics | 2021 |
| Tomo Solutions Limited | Information & communication | 2010 |
| Tomorrow Technologies & Services (T2S) Ltd | Information & communication | 2019 |
| Tonmark Drylining Ltd | Construction | 2006 |
| Tony O'Brien Photography Limited | Professional & scientific | 2017 |
| Tony's Painting and Decorating Ltd | Construction | 2026 |
| Tony's Window Cleaning Ltd | Administrative & support | 2024 |
| Tool Accessories Ltd | Wholesale & retail | 2022 |
| Top Draw Sports Ltd | Arts & recreation | 2024 |
| Top Glaze Improvements Limited | Construction | 2019 |
| Top to Bottom Developers Limited | Construction | 2020 |
| TOP1 Recruitment Limited | Administrative & support | 2025 |
| Topclean Finish Ltd | Administrative & support | 2025 |
| Toplift Scaffolding Limited | Construction | 2008 |
| Topnotch Property MGT (UK) Ltd | Real estate | 2020 |
| Topteam Support (UK) Ltd | Hospitality | 2023 |
| Topy Wala Ltd | Wholesale & retail | 2022 |
| Toria's Associates Limited | Administrative & support | 2013 |
| Torque & Trade Ltd | Wholesale & retail | 2025 |
| Torque Developments International Limited | Wholesale & retail | 1994 |
| TOS Services Ltd | Wholesale & retail | 2025 |
| Tosap Investment Limited | Financial services | 2022 |
| Tosin Adeniyi Kolae Limited | Administrative & support | 2021 |
| Total Framing Solutions Ltd | Construction | 2018 |
| Total Freight & Shipping Services Ltd | Transport & logistics | 2022 |
| Total Ground Limited | Construction | 2022 |
| Total New Home Ltd | Construction | 2019 |
| Total Protection Services Ltd | Administrative & support | 2019 |
| Totalnet Consultants Limited | Information & communication | 2011 |
| Touch of Grace Limited | Other services | 2025 |
| Tougeda Limited | Health & social care | 2013 |
| Tower Building Services Ltd | Construction | 2023 |
| Town & Country Surfacing Ltd | Construction | 2020 |
| Town Wharf (Grays) Management Company Limited | Households | 2004 |
| Town Wharf RTM Company Ltd | Households | 2011 |
| TPA Logistics Limited | Transport & logistics | 2023 |
| Tpbjj Ltd | Arts & recreation | 2025 |
| Tqubed Ltd | Extraterritorial | 2017 |
| Trace Measurement Limited | Manufacturing | 1989 |
| Trackster London Limited | Administrative & support | 2022 |
| Trade Your Home Ltd | Real estate | 2023 |
| Traderspro Limited | Wholesale & retail | 2020 |
| Tradewinds Flat Management Company Limited | Households | 1977 |
| Traditions Food Limited | Other services | 2018 |
| Trafalgar Security Solutions Limited | Administrative & support | 2013 |
| Trafficcake Limited | Professional & scientific | 2012 |
| Trainerscity Limited | Wholesale & retail | 2020 |
| Training & Coaching Solutions Limited | Professional & scientific | 2011 |
| Trans 7 Ltd | Transport & logistics | 2016 |
| Trans Christian Ltd | Transport & logistics | 2015 |
| Trans ROM Ltd | Transport & logistics | 2016 |
| Trans Star Ltd | Construction | 2015 |
| Trans-Chriss Ltd | Transport & logistics | 2012 |
| Trans-Erik Limited | Transport & logistics | 2013 |
| Trans-Vol | Transport & logistics | 2000 |
| Transclear Limited | Transport & logistics | 1981 |
| Transformiq Ltd | Information & communication | 2026 |
| Transitserv Ltd | Transport & logistics | 2018 |
| Transpit Ltd | Transport & logistics | 2024 |
| Transport AG Ltd | Transport & logistics | 2021 |
| Transport RM Ltd | Wholesale & retail | 2018 |
| Transport Sandu Limited | Transport & logistics | 2021 |
| Transport Solution Nationwide Ltd | Transport & logistics | 2019 |
| Transvito Limited | Transport & logistics | 2015 |
| Transweld Commercial Services Limited | Wholesale & retail | 2004 |
| Trasa Management Ltd. | Households | 2001 |
| Traxo Fleet Ltd | Transport & logistics | 2025 |
| Trebor Works Limited | Other services | 2018 |
| Treetops Learning Community | Education | 2017 |
| Tremulous Ltd | Financial services | 2019 |
| Trend District Ltd | Wholesale & retail | 2024 |
| Trentnest Ltd | Wholesale & retail | 2026 |
| Trentside Geotechnical Testing and Site Investigations Limited | Construction | 2014 |
| TRG Solutions Limited | Construction | 2018 |
| Triabite Foods Ltd | Wholesale & retail | 2026 |
| Tridecka Ltd | Professional & scientific | 2026 |
| Tring Property Services Limited | Real estate | 2024 |
| Tring Security Services Limited | Administrative & support | 2023 |
| Tring Staff Solutions Limited | Administrative & support | 2023 |
| Trinitas Healthcare Partners Ltd | Professional & scientific | 2023 |
| Trinity Essex Accountancy Limited | Professional & scientific | 2026 |
| Triple GEE Ltd | Real estate | 2025 |
| Triple O Group Limited | Wholesale & retail | 2022 |
| Triple O Holdings Ltd | Financial services | 2025 |
| Triple O Properties Solutions Limited | Real estate | 2022 |
| Triple R Motors Limited | Wholesale & retail | 2025 |
| Triple RD Ltd | Construction | 2019 |
| Trisha KAY Limited | Health & social care | 2016 |
| Triumph Care Group Limited | Health & social care | 2019 |
| Triumphant Child CIC | Health & social care | 2025 |
| Trivalak Ltd | Construction | 2018 |
| TRM Keep Clean Ltd | Administrative & support | 2018 |
| True Grounds Coaching Ltd | Other services | 2025 |
| True Landscaping Ltd | Administrative & support | 2020 |
| True Pharma Limited | Wholesale & retail | 2025 |