| THE Woofing LOT Ltd | Other services | 2025 |
| The.Content.Creators Ltd | Information & communication | 2019 |
| Theamata Consulting Limited | Administrative & support | 2016 |
| Theatre Bistro Ltd | Hospitality | 2026 |
| Theatre Gym Company Limited | Arts & recreation | 2026 |
| Thebayclothing Ltd | Extraterritorial | 2020 |
| Thedoghouse Enterprises Limited | Hospitality | 2025 |
| Thegowernook Ltd | Real estate | 2025 |
| Theispecialist Ltd | Information & communication | 2023 |
| Thekozaafba Ltd | Wholesale & retail | 2025 |
| Them Car Guys Ltd | Wholesale & retail | 2023 |
| Them Paint Guys Limited | Wholesale & retail | 2024 |
| Themagickey Ltd | Administrative & support | 2026 |
| Thenutritest Limited | Health & social care | 2025 |
| Theory Dental Ltd | Health & social care | 2024 |
| Therahub Ltd | Information & communication | 2025 |
| Therapy Solutions Ltd | Health & social care | 2010 |
| Thermaglaze Home Improvements Ltd | Wholesale & retail | 2020 |
| Thermal Insulation Co. Limited | Construction | 1999 |
| Thermaplas Ltd | Construction | 2025 |
| Thermavolt Energy Solutions Ltd | Construction | 2025 |
| Thermovey (Southern) Limited | Professional & scientific | 2015 |
| Thermox Limited | Manufacturing | 2004 |
| Thesalesshop Ltd | Wholesale & retail | 2025 |
| Thesofahub Ltd | Wholesale & retail | 2025 |
| THG Corporate Travel Limited | Administrative & support | 2020 |
| THG Holidays Limited | Administrative & support | 2020 |
| THG Travel Limited | Information & communication | 2007 |
| Think Switch Ltd | Other services | 2023 |
| Think VEN Ltd | Professional & scientific | 2018 |
| Third GEN Development Ltd | Real estate | 2026 |
| Third Phase Peac Limited | Information & communication | 2023 |
| Third Stone Interior Solutions Ltd | Construction | 2019 |
| Thirsty Marketing Ltd | Professional & scientific | 2023 |
| Thistle Studios CYF. | Information & communication | 2026 |
| Thistleboon Limited | Financial services | 2021 |
| Thomas & Green Plumbing & Heating Ltd | Construction | 2022 |
| Thomas CMS (Holdings) Ltd | Construction | 2003 |
| Thomas Davies Associates Limited | Professional & scientific | 2010 |
| Thomas Design (UK) Ltd | Information & communication | 2014 |
| Thomas Electrical Services Swansea Limited | Construction | 2016 |
| Thomas Energy Services Limited | Other services | 2013 |
| Thomas Financial Services Ltd | Financial services | 2014 |
| Thomas Kelly Services Limited | Manufacturing | 2013 |
| Thomas Parry Design Limited | Professional & scientific | 2020 |
| Thomas Properties (Mumbles) Limited | Real estate | 2017 |
| Thomas Safety Consultancy Limited | Administrative & support | 2014 |
| Thomas Scourfield & Sons | Mining & quarrying | 1999 |
| Thomas Thomas and Sons (Swansea) Limited | Real estate | 1948 |
| Thomas-Hunte Solutions Limited | Professional & scientific | 2012 |
| Thomassess Limited | Health & social care | 2025 |
| Thomprop Limited | Real estate | 2016 |
| Thompson & Shell Transport Limited | Transport & logistics | 2015 |
| Thompson Executive Travel Limited | Transport & logistics | 2017 |
| Thomson Consultant Services Ltd | Other services | 2023 |
| Thor Design UK Ltd | Information & communication | 2005 |
| Thorney Development Ltd | Construction | 2024 |
| Thornton Taverns Ltd | Hospitality | 2025 |
| Thorntons Lifestyle Carpets Limited | Wholesale & retail | 2004 |
| Thoughtful Profit Ltd | Wholesale & retail | 2019 |
| Thow for ALL Nations CIC | Other services | 2022 |
| Thread IT Ltd | Wholesale & retail | 2023 |
| Three Cliffs Cleaning Ltd | Administrative & support | 2022 |
| Three Cliffs Construction Limited | Construction | 2013 |
| Three Cliffs Events Ltd | Arts & recreation | 2020 |
| Three Cliffs Geomechanical Analysis Limited | Professional & scientific | 2008 |
| Three Cliffs Investments Company Limited | Financial services | 1986 |
| Three Cliffs Lettings Ltd | Real estate | 2021 |
| Three Cliffs Ltd | Wholesale & retail | 2024 |
| Three Cliffs Music Ltd | Information & communication | 2012 |
| Three Cliffs Productions Limited | Arts & recreation | 2002 |
| Three Cliffs Properties Ltd | Real estate | 2024 |
| Three Cliffs Quality Management Systems Ltd. | Manufacturing | 2020 |
| Three Crosses (Management Company) Limited | Real estate | 2005 |
| Three Healthcare Limited | Health & social care | 2012 |
| Three Phase Ltd | Construction | 2026 |
| Three-Sixty Aquaculture Limited | Agriculture & fishing | 2014 |
| Threshold Property Management Limited | Real estate | 2008 |
| Threshold Sales Limited | Real estate | 2018 |
| Thsm Developments Ltd | Construction | 2025 |
| Thyme Outside Ltd | Hospitality | 2014 |
| TI Akinwumi Limited | Health & social care | 2024 |
| TIC Inspection Consultants Ltd | Professional & scientific | 2014 |
| TICKET247 Ltd | Administrative & support | 2020 |
| Tidal Anchors Holdings Limited | Manufacturing | 2017 |
| Tidal Cleaning Ltd | Administrative & support | 2021 |
| Tidal Develop and Construct Ltd | Construction | 2026 |
| Tidal Estates and Lettings Limited | Real estate | 2017 |
| Tidal Exhibitions Limited | Administrative & support | 2018 |
| Tidal Property Limited | Real estate | 2022 |
| Tide Advisory Ltd | Professional & scientific | 2022 |
| Tidi-Cable Products (UK) Limited | Construction | 2019 |
| Tidy Tyres Limited | Wholesale & retail | 2012 |
| Tidybuild Ltd | Construction | 2016 |
| Tifa One CIC | Health & social care | 2024 |
| Tiger Burrows Limited | Professional & scientific | 2022 |
| Tiger Developments & Management Ltd | Construction | 2017 |
| Tiger Lane Group Limited | Information & communication | 2016 |
| Tightly Woven Limited | Arts & recreation | 2023 |
| Tile Kiln Consultants Limited | Construction | 2013 |