| TR Property Services Ltd | Real estate | 2019 |
| Trackerpoint Limited | Information & communication | 2009 |
| Tracks (Autism) | Education | 2004 |
| Tracy Macassey Ltd | Information & communication | 2021 |
| Trade Foam Removal Ltd | Construction | 2024 |
| Tradeops AI Limited | Information & communication | 2026 |
| Trading Teacher Online Ltd | Education | 2019 |
| Trafalgar Decor London Ltd | Construction | 2022 |
| Trafalgar Decor UK Limited | Construction | 2019 |
| Traffic Junction Limited | Information & communication | 2003 |
| Training 360UK Limited | Other services | 2024 |
| Trans Moore Solutions Ltd | Professional & scientific | 2018 |
| Transformative Risk Solutions Ltd | Information & communication | 2021 |
| Transitional Steps Ltd | Education | 2025 |
| Tranters Mews Management Company Limited | Households | 2010 |
| Tranzpro Limited | Transport & logistics | 2014 |
| Traqa Limited | Professional & scientific | 1997 |
| Travel Designed Limited | Administrative & support | 2021 |
| Travel Spot LLP | | 2007 |
| Travel Technology Consulting Limited | Information & communication | 2023 |
| Travel With BEN Ltd | Professional & scientific | 2024 |
| Tree House 23 Limited | Hospitality | 2016 |
| Tree Lovers Limited | Administrative & support | 2010 |
| Tresman Limited | Administrative & support | 2011 |
| TRI Estates & Developments Ltd | Real estate | 2025 |
| Triangle Integrated Services Limited | Extraterritorial | 2016 |
| Triangle Pre-School Community Interest Company | Education | 2010 |
| Trickcyclists Ltd | Information & communication | 2014 |
| Trident Digital Media Limited | Arts & recreation | 2017 |
| Trident Live Events Ltd | Administrative & support | 2023 |
| Trilist Limited | Information & communication | 2013 |
| Trimco Services Ltd | Construction | 2020 |
| Trimco Services(London) Limited | Construction | 2020 |
| Trinity Electrical Services (London) Ltd | Construction | 2022 |
| Trinity House (Fairford Leys) Aylesbury Management Company Limited | Households | 2001 |
| Trinity Place Management Company (Stevenage) Limited | Households | 1980 |
| Trinity Place Management Company NO. 2 (Stevenage) Limited | Households | 1983 |
| Trinity Walk (Stevenage) Management Company Limited | Households | 2006 |
| Tripandey Estates Ltd | Real estate | 2019 |
| Tripillar Property Limited | Real estate | 2025 |
| Triple a Reality Ltd | Real estate | 2025 |
| Triple D Support Services Limited | Administrative & support | 2013 |
| Triple S Estates Ltd | Real estate | 2020 |
| Triplicate Properties Ltd | Real estate | 2021 |
| Trisk BIO Ltd | Information & communication | 2020 |
| Tristar (UK) Ltd. | Wholesale & retail | 1994 |
| Triumph SEN and Wellbeing Services Ltd | Health & social care | 2021 |
| Triumvirate Limited | Health & social care | 2025 |
| Trog Studios Ltd | Information & communication | 2022 |
| Trogle Ltd | Real estate | 2017 |
| Troian Ltd | Construction | 2016 |
| Troopers Recruitment Limited | Administrative & support | 2025 |
| TRS Secretaries Limited | Professional & scientific | 2006 |
| Truc Fierce Ltd | Information & communication | 2018 |
| Trucare Companionship Limited | Health & social care | 2026 |
| Truclean Cleaning Services Ltd | Administrative & support | 2019 |
| True Sky Vets Limited | Professional & scientific | 2024 |
| True Vital Limited | Health & social care | 2025 |
| Truefield Ltd | Other services | 2025 |
| Truegraft Ltd | Construction | 2025 |
| Trumpington Estates Limited | Real estate | 1994 |
| Trunk Trunk Limited | Information & communication | 2016 |
| Trusst Group Limited | Professional & scientific | 2026 |
| Trust Built Ltd | Other services | 2024 |
| Trustatrader.Com Limited | Professional & scientific | 2005 |
| Trusted Jobs Limited | Agriculture & fishing | 2025 |
| Trusted Payments Limited | Financial services | 2022 |
| Trustwater Limited | Professional & scientific | 2016 |
| TS Career Coaching Limited | Administrative & support | 2022 |
| Tsang YIP Properties Ltd | Real estate | 2023 |
| Tsr-Direct Ltd | Wholesale & retail | 2022 |
| Tudor Healthcare Limited | Health & social care | 2021 |
| Tudor Square Management Company Limited | Households | 2003 |
| Tuli Plains Ltd | Professional & scientific | 2012 |
| Tune Skool Ltd | Education | 2020 |
| Turcaz Limited | Construction | 2020 |
| Turkuaz Tunbridge Wells Limited | Hospitality | 2021 |
| Turn Buffalo Ltd | Information & communication | 2022 |
| Turner & Hendry Ltd | Construction | 2018 |
| Turnpike Consultant Limited | Construction | 2020 |
| Turquoise Aesthetics & Beauty Ltd | Other services | 2024 |
| Turtle Events & Hospitality Ltd | Hospitality | 2026 |
| Turtle Events Ltd | Hospitality | 2025 |
| Tutorlink Limited | Real estate | 1986 |
| Tuvgan Ltd | Real estate | 2019 |
| TW Corporatewear Limited | Manufacturing | 2007 |
| TWB Bristol Limited | Real estate | 2025 |
| Tweidpharma Limited | Wholesale & retail | 2022 |
| Twenty SN Limited | Construction | 2006 |
| Two Bees Brewing Limited | Professional & scientific | 2022 |
| Two Bridges Limited | Health & social care | 2019 |
| Two Shoes Creative Ltd | Professional & scientific | 2020 |
| Twobit Holdings Limited | Financial services | 2024 |
| Twpb Financial Services Limited | Professional & scientific | 2020 |
| TYA Paving Ltd | Construction | 2023 |
| Tyagi Anaesthetic Services Ltd | Health & social care | 2022 |
| Tyco Travel Limited | Administrative & support | 2009 |
| Tygerman Consulting Ltd | Information & communication | 2017 |
| Tyre Geeks Ltd | Wholesale & retail | 2019 |
| Tyrer Plumbing & Heating Limited | Construction | 2022 |