| Thejones London Limited | Professional & scientific | 2015 |
| Thenailscompany Limited | Other services | 2016 |
| Theo Morrant Kitchen Installers Ltd | Construction | 2014 |
| Theonepercent% Ltd | Manufacturing | 2025 |
| Therailcompany Limited | Construction | 2025 |
| Therapy & Coaching Consultancy Ltd | Health & social care | 2023 |
| Thermo Heating & Plumbing (UK) Limited | Construction | 2007 |
| Thesouthdesign Ltd | Professional & scientific | 2024 |
| THETSANE1 Limited | Administrative & support | 2020 |
| Theuches Ltd | Information & communication | 2018 |
| Theva Trades Ltd | Wholesale & retail | 2024 |
| Thewellnessblackcard Ltd | Health & social care | 2025 |
| Thewg Ltd | Wholesale & retail | 2023 |
| THG Solutions Limited | Financial services | 2015 |
| THH Enterprises Ltd | Professional & scientific | 2025 |
| Thiago Motorcycle Ltd | Wholesale & retail | 2026 |
| Thila Groups Limited | Hospitality | 2023 |
| Things U Need NOW Ltd | Wholesale & retail | 2024 |
| Think Ahead Data Consultancy Ltd | Information & communication | 2024 |
| Think BIT Consulting Ltd | Information & communication | 2019 |
| Think Events Management Ltd | Arts & recreation | 2016 |
| Think IT Korpo 2IA LLP | | 2019 |
| Think-I Ltd | Arts & recreation | 2025 |
| Thinkalize Global Ltd | Information & communication | 2020 |
| Thinkdevops Limited | Information & communication | 2013 |
| Thinkinvesty Limited | Financial services | 2025 |
| Thinnaiuk Limited | Hospitality | 2024 |
| Third Bagleys Lane Management Company Limited | Households | 1982 |
| Third Paddock Wood Residents Association Limited(The) | Households | 1985 |
| Third Pilgrims Management Company Limited | Other services | 1987 |
| Third Strand Health Limited | Education | 2024 |
| Thirsty Media Ltd | Information & communication | 2026 |
| Thirteen Farquharson Road Management Company Limited | Real estate | 1988 |
| Thirty-Nine Courtfield Gardens Freehold Limited | Households | 1997 |
| Thirty-Thirty Ltd | Information & communication | 2016 |
| This IS Living Pilates Ltd | Health & social care | 2005 |
| This IS My Timepiece Ltd | Information & communication | 2018 |
| Thistlewood 63 Limited | Extraterritorial | 2013 |
| THM Croydon Ltd | Manufacturing | 2026 |
| THM South Ltd | Wholesale & retail | 2015 |
| Thoghay Estates Ltd | Real estate | 2025 |
| Thokozani Limited | Transport & logistics | 2008 |
| Thomas &Family Security Limited | Financial services | 2024 |
| Thomas Books Ltd | Professional & scientific | 2024 |
| Thomas Court Management Company Limited | Other services | 2003 |
| Thomas Creative Ltd | Arts & recreation | 2010 |
| Thomas Dare Limited | Wholesale & retail | 1990 |
| Thomas DE Cruz Media Ltd | Information & communication | 2019 |
| Thomas Graves Partnership LLP | | 2019 |
| Thomas Living Ltd | Hospitality | 2025 |
| Thomas Way (Braintree) Management Company Limited | Households | 2012 |
| Thomascuts Limited | Administrative & support | 2017 |
| Thommo's Drivers Ltd | Transport & logistics | 2020 |
| Thompson Advisory Group Ltd | Professional & scientific | 2026 |
| Thompson Hills Ltd | Real estate | 2023 |
| Thompsons (UK) Holdings Limited | Professional & scientific | 2015 |
| Thompsons (UK) Limited | Manufacturing | 1973 |
| Thompsons Aluminium Ltd | Extraterritorial | 2013 |
| Thompsons Eparts Limited | Wholesale & retail | 2015 |
| Thompsons Rental Solutions Ltd | Real estate | 2025 |
| Thompsons Servicetech Ltd | Manufacturing | 1987 |
| Thompsons Waste Handling Equipment Limited | Water & waste | 2021 |
| Thong Heng Foods Limited | Wholesale & retail | 2006 |
| Thorcourt Estates Limited | Real estate | 1939 |
| Thorn House (56 ST Johns Park) Management Limited | Real estate | 2001 |
| Thornbury Court Management Company Limited | Households | 1982 |
| Thorndale Sutton-Thorndale Properties Ltd | Real estate | 2023 |
| Thorndon Court Limited | Households | 1981 |
| Thorne Apartments (Management) Limited | Households | 1984 |
| Thorne Meadows (Great Eccleston) Management Company Limited | Households | 2017 |
| Thorne Meadows Phase 2 Management Company Limited | Households | 2020 |
| Thornhill Croydon Ltd | Real estate | 2014 |
| Thornton Accountants Ltd | Professional & scientific | 2017 |
| Thornton Heath Builders Limited | Construction | 2019 |
| Thornton Road Hand Car Wash Ltd | Administrative & support | 2022 |
| Thornton Roofing Solutions Ltd | Construction | 2024 |
| Thornton Services Limited | Professional & scientific | 2009 |
| Thornton Timber Ltd | Construction | 2020 |
| Thornwood Gardens (Freehold) Limited | Households | 2009 |
| Thornwood Gardens Investments Limited | Households | 2010 |
| Thorpe Close(Hornchurch)Management Co.Limited | Households | 1973 |
| Thorpe Property Services Ltd | Households | 2026 |
| Thos. C. Fuller & SON Limited | Transport & logistics | 2003 |
| Thoughtcraft Ltd | Information & communication | 2015 |
| Thoughtful Services Limited | Other services | 2001 |
| Thoughtwheels Limited | Information & communication | 2015 |
| Thraceline Ltd | Construction | 2025 |
| Thread and Anchor Ltd | Education | 2025 |
| Thrive and Create Ltd | Professional & scientific | 2025 |
| Thriveo Limited | Information & communication | 2026 |
| Thropharm Ltd | Health & social care | 2019 |
| Thunder Coach Ltd | Administrative & support | 2026 |
| Thunder Weld Fabrication Ltd | Manufacturing | 2018 |
| Thung Ngein Thung Thong Limited | Hospitality | 2024 |
| Thurai Auto Services Ltd | Manufacturing | 2010 |
| Thurland Limited | Real estate | 1991 |
| Thurlow Brown Limited | Professional & scientific | 2013 |
| Thurlow Court E11 Limited | Households | 2022 |
| THY Holy Co Ltd. | Financial services | 2025 |
| THZ Custom Workshop Ltd | Wholesale & retail | 2022 |