| Trail Goats Limited | Administrative & support | 2025 |
| Trailer Training UK Limited | Education | 2009 |
| Trakmark Limited | Other services | 2021 |
| Tramex Limited | Wholesale & retail | 2023 |
| Tranquility Contractors Limited | Construction | 2022 |
| Trans-Continental Corporation Limited | Transport & logistics | 1990 |
| Trans-Kal Ltd | Transport & logistics | 2017 |
| Transbusiness Limited | Extraterritorial | 1998 |
| Transcargo OVI Ltd | Transport & logistics | 2024 |
| Transcendance Ltd | Other services | 2014 |
| Transcreen Educational Films Limited | Education | 1988 |
| Transform Africa NOW Ltd | Other services | 2023 |
| Transform Landscape Services Limited | Administrative & support | 2016 |
| Transform Venue Ltd | Professional & scientific | 2013 |
| Transformational Physiotherapy Ltd | Health & social care | 2026 |
| Transframe Ltd | Professional & scientific | 2024 |
| Transg Ltd | Construction | 2024 |
| Transglobeconsulting Limited | Professional & scientific | 2012 |
| Transilvania&Co Limited | Wholesale & retail | 2011 |
| Transition Engineering Consultancy Ltd | Professional & scientific | 2021 |
| Transmatt Ltd | Transport & logistics | 2025 |
| Transmov Limited | Professional & scientific | 2008 |
| Transporglau Ltd | Transport & logistics | 2024 |
| Transport Class Ltd | Transport & logistics | 2016 |
| Transport FKM Ltd | Transport & logistics | 2022 |
| Transport GJ Ltd | Transport & logistics | 2011 |
| Transport JKM Ltd | Transport & logistics | 2019 |
| Transport PPM Ltd | Transport & logistics | 2019 |
| Transport Supply and Solutions Ltd | Professional & scientific | 2025 |
| Transporty Hireuk Ltd | Transport & logistics | 2025 |
| Transylvania's Yard Ltd | Hospitality | 2021 |
| Trant Engineering Limited | Construction | 1963 |
| Trant Engineering Services Limited | Construction | 2019 |
| Trant Estates Limited | Real estate | 1986 |
| Trant Holding Company Limited | Professional & scientific | 2013 |
| Trapcia Transport Ltd | Transport & logistics | 2015 |
| Trash Gallery Ltd | Manufacturing | 2020 |
| Trauma Response Network Limited | Other services | 2017 |
| Travel Education Experiences Ltd | Administrative & support | 2019 |
| Travel Guru Services Ltd | Administrative & support | 2025 |
| Travel Managers Group Limited | Professional & scientific | 2006 |
| Travel Mobility Solutions Ltd | Wholesale & retail | 2025 |
| Travel Visit Explore Limited | Administrative & support | 2021 |
| Travelusion Ltd | Administrative & support | 2021 |
| Travelwithsicklecell Ltd | Health & social care | 2025 |
| Travis Engineering Ltd | Information & communication | 2011 |
| Travolta Electrical Services Ltd | Construction | 2020 |
| Trayana Realty Ltd | Real estate | 2025 |
| Traystone Management Ltd | Administrative & support | 2010 |
| Traystone Ukeig | | 2010 |
| Trebe Estates Ltd | Real estate | 2011 |
| Tredon Limited | Professional & scientific | 2002 |
| Trees on Farms Limited | Agriculture & fishing | 2024 |
| Treesolve Ltd | Administrative & support | 2023 |
| Treetops Chilworth Management Company Limited | Households | 2007 |
| Tremona Court Management Company Limited | Households | 1987 |
| Tremor Electrical Ltd | Construction | 2008 |
| Trench Town Kitchen Limited | Hospitality | 2020 |
| Trend Emporium Limited | Extraterritorial | 2023 |
| Trendalt Ltd | Wholesale & retail | 2024 |
| Trendcares Limited | Administrative & support | 2020 |
| Trendify Markit Ltd | Wholesale & retail | 2025 |
| Trendloop Limited | Real estate | 2002 |
| Trendsblue Medics Ltd | Professional & scientific | 2024 |
| Trendwise AI Ltd | Information & communication | 2025 |
| Trenholme Valves Limited | Wholesale & retail | 2018 |
| Trent Services (Southampton) Ltd | Construction | 2002 |
| Trenza Braid Bar Ltd | Other services | 2019 |
| Trethowans Services (NO 2) Limited | Professional & scientific | 2001 |
| Trethowans Services Limited | Professional & scientific | 1994 |
| Trevipark Limited | Construction | 2005 |
| Trevor Jones Contracting Limited | Construction | 1999 |
| Trevor Williams (Builders) Limited | Wholesale & retail | 1961 |
| Treycourt Limited | Administrative & support | 2003 |
| TRF Healthcare II Ltd | Administrative & support | 2023 |
| TRF Healthcare Ltd | Administrative & support | 2022 |
| TRI Exforces Ltd | Administrative & support | 2014 |
| Triangle (Berth Brokers) Limited | Professional & scientific | 1990 |
| Triangle Hospitality Ltd | Hospitality | 2014 |
| Triangle Laundry Ltd | Other services | 2024 |
| Triangle Lounge Limited | Hospitality | 2011 |
| Triangle Spice Limited | Hospitality | 2025 |
| Triatis Global Ltd | Professional & scientific | 2019 |
| Tribal K9 Ltd | Other services | 2026 |
| Tribbeck Property Ltd | Real estate | 2021 |
| Tribbles Plumbing & Heating Ltd | Construction | 2014 |
| Tribeca Consulting Ltd | Information & communication | 2021 |
| Trident GAS Limited | Construction | 2024 |
| Trident Health and Safety Ltd | Professional & scientific | 2016 |
| Trident Powders Ltd | Manufacturing | 2015 |
| Triggerfish IT Limited | Information & communication | 1998 |
| Trigpoint Ltd | Information & communication | 2002 |
| Trilogix Limited | Financial services | 2011 |
| Trilogy Consulting Group Ltd | Professional & scientific | 2022 |
| Trimmers Limited | Administrative & support | 2009 |
| Trimwise Fitness Limited | Arts & recreation | 2013 |
| Trinder House Investments Limited | Agriculture & fishing | 2005 |
| Trinity Barber Club Ltd | Other services | 2026 |
| Trinity Bathrooms Ltd | Wholesale & retail | 2022 |
| Trinity Business Investments Limited | Professional & scientific | 2015 |