| Thinkengine Limited | Administrative & support | 2013 |
| Thinking Dimensions Global (PTY) Limited | Information & communication | 2015 |
| Thinking Web Ltd | Information & communication | 2019 |
| Thinklesticks Ltd | Arts & recreation | 2020 |
| Thinkscape Group Limited | Financial services | 2023 |
| Thinkscape Holdings Limited | Financial services | 2016 |
| Thinkscape Limited | Information & communication | 1998 |
| Thinkteractive Ltd | Administrative & support | 2009 |
| Third Sector Legal Consulting Ltd | Professional & scientific | 2026 |
| Thirteen HR Limited | Professional & scientific | 2019 |
| This IS Clearcut Ltd | Professional & scientific | 2016 |
| Thistle Ledge Limited | Real estate | 2009 |
| Thistles Homes Limited | Real estate | 2025 |
| Thomar Associates Ltd | Administrative & support | 2020 |
| Thomas Croft Limited | Professional & scientific | 2002 |
| Thomas Daniel Gibbons Ltd | Wholesale & retail | 2026 |
| Thomas Harper Group Ltd | Wholesale & retail | 2024 |
| Thomas Homes Limited | Construction | 2003 |
| Thomas Ltd | Construction | 2004 |
| Thomas Newco Limited | Financial services | 2025 |
| Thomas Rose Homes Limited | Extraterritorial | 2025 |
| Thomas Ross Limited | Information & communication | 1985 |
| Thompson Commercial Surveyors Limited | Professional & scientific | 2018 |
| Thompson Insulation Limited | Construction | 2002 |
| Thompson International Holdings Limited | Administrative & support | 2009 |
| Thompson Trucks Limited | Wholesale & retail | 2009 |
| Thompson's Property Services Limited | Other services | 2015 |
| Thomson Associates Limited | Real estate | 1997 |
| Thomson Avenue Ltd | Information & communication | 2016 |
| Thomtrucks Limited | Wholesale & retail | 2008 |
| Thong WAI Takeaway Limited | Hospitality | 2025 |
| Thor and Phoenix Ltd | Wholesale & retail | 2025 |
| Thorloki Limited | Hospitality | 2019 |
| Thorne Fencing Limited | Construction | 2022 |
| Thornetts LH Limited | Construction | 2021 |
| Thornhill Oral Health Ltd | Health & social care | 2026 |
| Thornhill Park Ltd | Wholesale & retail | 2025 |
| Thornhurst Property Management Limited | Real estate | 2002 |
| Thornleigh Limited | Construction | 2024 |
| Thorold Electrical Services Ltd | Construction | 2014 |
| Thorpe Hall Mansions (New Block) RTM Company Ltd | Households | 2022 |
| Thorpe Hall Mansions (Old Block) RTM Company Ltd | Households | 2022 |
| Thoughtlounge Ltd | Education | 2013 |
| Three Bears Wood Limited | Agriculture & fishing | 2021 |
| Three Coats Limited | Real estate | 2008 |
| Three D Nails 196 Ltd | Other services | 2026 |
| Three Lions Automotive Ltd | Wholesale & retail | 2026 |
| Three Rivers Property Management Company Limited | Households | 2017 |
| Three Tens Consultancy Limited | Information & communication | 2025 |
| Three Tuns Henley Ltd | Hospitality | 2021 |
| Threshold Financial Services Limited | Financial services | 2004 |
| Threshold Group Limited | Financial services | 2018 |
| Threshold Mortgage Advice Limited | Financial services | 2017 |
| Threshold Properties & Investments Limited | Real estate | 2018 |
| Threshold Security Systems Limited | Administrative & support | 2016 |
| Threshold Wealth Management Limited | Financial services | 2020 |
| Thrive & Revive Aesthetics Ltd | Other services | 2021 |
| Thrive Holistic UK Ltd | Wholesale & retail | 2021 |
| Thrive Investments Limited | Real estate | 2022 |
| Thrive Psychological Wellbeing Services Ltd | Health & social care | 2025 |
| Thrive Wellness Centre Ltd | Health & social care | 2024 |
| Thriving Mind Therapy Limited | Health & social care | 2021 |
| Thruness Ltd | Information & communication | 2026 |
| THT Property Limited | Real estate | 2020 |
| Thufuskard Limited | Administrative & support | 2025 |
| Thunder Pressure Ltd | Administrative & support | 2022 |
| Thunder Transport Ltd | Transport & logistics | 2022 |
| Thunder Volt Bikes Ltd | Manufacturing | 2025 |
| Thunderbolt Jointing Ltd | Other services | 2018 |
| Thunderbolt Properties Ltd | Real estate | 2024 |
| Thurston Image Solutions Ltd | Manufacturing | 2016 |
| Thurston UK Ltd | Manufacturing | 2016 |
| Tiaf Ltd | Wholesale & retail | 2017 |
| Tianyi Food Ltd | Hospitality | 2025 |
| Tibballs Properties Ltd | Real estate | 2023 |
| Tibs Housing (Cambridge) Limited | Real estate | 2023 |
| Tidal Force Solutions Ltd | Professional & scientific | 2024 |
| Tidal Harness Limited | Professional & scientific | 2014 |
| Tidal Plumbing and Heating Limited | Construction | 2017 |
| Tidal Pulse Media Ltd | Information & communication | 2016 |
| Tidal Vape Limited | Wholesale & retail | 2009 |
| Tidby Accounting & Business Solutions Limited | Professional & scientific | 2019 |
| Tide Property Management Ltd | Hospitality | 2020 |
| Tidy Touch Cleaning and Organising Company Limited | Wholesale & retail | 2023 |
| Tigertronics Ltd | Professional & scientific | 2019 |
| Tikraz Limited | Professional & scientific | 2026 |
| Tiktok Integration Limited | Professional & scientific | 2003 |
| Tiktok Limited | Professional & scientific | 2018 |
| Tilden Court Management RTM Company Limited | Households | 2023 |
| Tiles and More Ltd | Manufacturing | 2025 |
| Tilis Ultra Motors Ltd | Wholesale & retail | 2024 |
| Tillo and Partner Company Ltd | Wholesale & retail | 2022 |
| Tilly Industries Ltd | Hospitality | 2023 |
| Tilly Place Management Company Limited | Administrative & support | 2014 |
| Tilt Partners Limited | Professional & scientific | 2021 |
| TIM Abraham Ltd | Professional & scientific | 2003 |
| TIM Hughes Hair Limited | Other services | 2015 |
| TIM Taylor Photography Limited | Professional & scientific | 2009 |
| Timar Transport Ltd | Transport & logistics | 2020 |
| Timariu Ltd | Transport & logistics | 2016 |