| Total Commissioning Management Ltd | Professional & scientific | 2018 |
| Total Constructions & Management Limited | Water & waste | 2024 |
| Total Pets UK Ltd | Wholesale & retail | 2026 |
| Total Projects Limited | Education | 2005 |
| Totally Independent Communications Ltd | Professional & scientific | 2001 |
| Toti Properties Ltd | Real estate | 2026 |
| Tots-R-Us Limited | Health & social care | 2003 |
| Totteridge House Residents Limited | Real estate | 2000 |
| Touch of Class Carpets Ltd | Construction | 2019 |
| Tour & Travel Village Ltd | Administrative & support | 2025 |
| Tower Bridge Consultancy & Training | Professional & scientific | 2011 |
| Tower House (Loudwater) Management Limited | Households | 1988 |
| Town END Court Management Limited | Households | 2007 |
| Town Link Transport Limited | Transport & logistics | 2008 |
| Town Wharf (1) Management Company Limited | Households | 1996 |
| Town Wharf (2) Management Company Limited | Households | 1996 |
| Town Wharf (3) Management Company Limited | Households | 1997 |
| Toyo Investment Consulting Limited | Professional & scientific | 2015 |
| Tozerplan Developments (Grove Bay) Limited | Real estate | 2021 |
| Tozerplan Developments Ltd | Real estate | 2016 |
| Tozerplan Developments Sudbury Limited | Real estate | 2017 |
| Tozerplan Limited | Wholesale & retail | 1981 |
| Tozerplan Properties Ltd | Real estate | 2014 |
| Tozerplan Properties Uxbridge Limited | Real estate | 2016 |
| TPA Construction Services Limited | Construction | 2025 |
| Tphmo Limited | Professional & scientific | 2025 |
| Tpls Interiors Ltd | Construction | 2006 |
| TPW & Sons Ltd | Construction | 2020 |
| Track Tales Production Ltd | Transport & logistics | 2023 |
| Trackdown Music Limited | Information & communication | 1997 |
| Tractionedge Ltd | Information & communication | 2025 |
| Trade Connections (Worldwide) Limited | Administrative & support | 2010 |
| Trade Growth Specialists Ltd | Information & communication | 2026 |
| Trade Sale (Slough) Limited | Wholesale & retail | 2002 |
| Trade Sale Ltd | Wholesale & retail | 1997 |
| Tradeopedia Ltd | Wholesale & retail | 2014 |
| Traderpharm Ltd | Wholesale & retail | 2019 |
| Tradexpo Limited | Real estate | 2019 |
| Trails of Africa (UK) Limited | Administrative & support | 2022 |
| Tran Holdings Ltd | Hospitality | 2024 |
| Trans-Afric Prime Services UK Limited | Wholesale & retail | 2018 |
| Transact BP Ltd | Information & communication | 2025 |
| Transact HP Ltd | Information & communication | 2025 |
| Transformation Talent Limited | Administrative & support | 2021 |
| Transglobe Limited | Transport & logistics | 2015 |
| Transito Cars Ltd | Transport & logistics | 2018 |
| Transixpress Ltd | Transport & logistics | 2026 |
| Translectrix Limited | Wholesale & retail | 2012 |
| Transportify Customs Limited | Transport & logistics | 2025 |
| Transportify Limited | Transport & logistics | 2019 |
| Tranter-Whyman Estates Ltd | Real estate | 2025 |
| Travel DOCTOR4U Ltd | Health & social care | 2025 |
| Travelair Limited | Transport & logistics | 2011 |
| Travelines Limited | Professional & scientific | 2011 |
| TRC Driving Ltd | Transport & logistics | 2019 |
| Trebor Bassett Limited | Manufacturing | 1907 |
| Trebor International Limited | Professional & scientific | 1958 |
| Trendy Dealz Limited | Wholesale & retail | 2025 |
| Trendy Outfit Ltd | Wholesale & retail | 2022 |
| Trevor Power Limited | Administrative & support | 2009 |
| Trevtia Limited | Manufacturing | 2026 |
| TRI Control Systems Ltd | Manufacturing | 1985 |
| Tri-Glade Cleaning Services Ltd | Administrative & support | 2010 |
| Triboband C.I.C. | Arts & recreation | 2019 |
| Trident Auto Engineers Ltd | Wholesale & retail | 2022 |
| Trident Global Technologies Ltd | Real estate | 2015 |
| Tridentrealm Limited | Professional & scientific | 2006 |
| Trifit Ltd | Arts & recreation | 2024 |
| Trillium Construction PVT Ltd | Construction | 2021 |
| Trim Hub Ltd | Other services | 2025 |
| Trimiti Limited | Wholesale & retail | 2025 |
| Trinidad - POT Ltd | Wholesale & retail | 2020 |
| Trinity Activities | Wholesale & retail | 1998 |
| Trinity Court Watford Management Limited | Households | 2002 |
| Trinity Homeless Projects | Hospitality | 2007 |
| Trinity London Concierge Limited | Professional & scientific | 2022 |
| Trinity Property Consultancy Limited | Construction | 2022 |
| Trinity Security Guards Ltd | Other services | 2015 |
| Trinity SET and Stage Ltd | Manufacturing | 2011 |
| Trip Planners Limited | Information & communication | 2024 |
| Tripflee Consolidator Private Limited | Administrative & support | 2024 |
| Triple West Medical Limited | Administrative & support | 2007 |
| Trish O'Hara Limited | Health & social care | 2013 |
| Trishan Services Limited | Information & communication | 2017 |
| Triton Business Finance Limited | Extraterritorial | 1986 |
| Triumph Wholesale Ltd | Wholesale & retail | 2024 |
| Triveni Care Limited | Real estate | 2019 |
| Troi Joinery & Carpentry Ltd | Construction | 2025 |
| Troika Property Investments Limited | Real estate | 2012 |
| Trojan Health and Fitness Ltd | Arts & recreation | 2021 |
| Trojan Security Corporation (UK) Limited | Manufacturing | 2011 |
| Tropic Sunrise Ltd | Extraterritorial | 2022 |
| Tropics Grill Ltd | Hospitality | 2023 |
| Troy Strategic Consulting Limited | Real estate | 2014 |
| TRU LI Tree Services Ltd | Agriculture & fishing | 2015 |
| Tru-Elements Ltd | Professional & scientific | 2023 |
| Truck Force Ltd | Transport & logistics | 2025 |
| Truck Inspection Ltd | Wholesale & retail | 2013 |
| True Image Ultrasound Ltd | Health & social care | 2025 |
| Trueheart Care Limited | Health & social care | 2025 |