| Trade Sealants Ltd. | Wholesale & retail | 1992 |
| Trade Velocity Ltd | Wholesale & retail | 2024 |
| TRADE0822 Limited | Wholesale & retail | 2022 |
| Tradepa Ltd | Information & communication | 2026 |
| Tradesmile Ltd | Wholesale & retail | 2024 |
| Tradewind Digital Ltd | Wholesale & retail | 2023 |
| Traditional and Modern Building Specialist Ltd | Construction | 2024 |
| Traditional Rides UK Ltd | Arts & recreation | 2018 |
| Trafalgar Talent Ltd | Administrative & support | 2024 |
| Train&Hustle Ltd | Wholesale & retail | 2025 |
| Training Development Solutions Limited | Education | 2005 |
| Training Vision Limited | Extraterritorial | 2009 |
| Transitioning Care Limited | Health & social care | 2022 |
| Transpaul Ltd | Transport & logistics | 2024 |
| Transport Collectables Limited | Wholesale & retail | 2021 |
| Trapani Vehicle Movements Ltd | Transport & logistics | 2021 |
| Trash Arts Ltd | Information & communication | 2016 |
| Trash Arts Open YA Mouth CIC | Arts & recreation | 2020 |
| Travel DAD Limited | Information & communication | 2021 |
| Travers Limited | Real estate | 2010 |
| Traybourne (Electrical) Limited | Wholesale & retail | 1989 |
| TRE Kernow Ltd | Real estate | 2022 |
| Treasure Education and Care Support Services Limited | Public administration | 2022 |
| Treasury Motors Limited | Wholesale & retail | 2025 |
| Tredsure Ltd | Construction | 2019 |
| Treloggan Wigs Ltd | Other services | 2005 |
| Trend and Bend Ltd | Wholesale & retail | 2024 |
| Trend Scoop Marketing Ltd | Administrative & support | 2019 |
| Trends and Spends Limited | Administrative & support | 2002 |
| Trento House Ltd | Professional & scientific | 2010 |
| Trevi Ltd | Real estate | 2011 |
| Trevose Holdings Ltd | Real estate | 2023 |
| Tri-Unity Consulting Ltd | Other services | 2020 |
| Triangle TEN Limited | Professional & scientific | 2010 |
| Triform Group Limited | Administrative & support | 2024 |
| Triick Ltd | Professional & scientific | 2020 |
| Trinder Shared Homes Limited | Real estate | 2015 |
| Trionex Solutions Limited | Information & communication | 2025 |
| Triple Axis Ltd | Construction | 2019 |
| Triple Dimension Ltd | Manufacturing | 2020 |
| Triple H Investments Ltd | Real estate | 2022 |
| Triple H Trading Limited | Wholesale & retail | 2023 |
| Triple M Healthcare Ltd | Health & social care | 2022 |
| Triple R Scaffolding Limited | Construction | 2024 |
| Triple T Investments Limited | Real estate | 2012 |
| Trippee Global Limited | Administrative & support | 2023 |
| Triton Global Structures Ltd | Construction | 2025 |
| Triumph Roofing & Cladding Limited | Construction | 2017 |
| Trixabella Limited | Wholesale & retail | 2020 |
| TRL Investments Limited | Financial services | 2022 |
| Trois Frères Concept Ltd | Hospitality | 2022 |
| Tronmec Ltd | Manufacturing | 2013 |
| Trouble in the Square Limited | Arts & recreation | 2023 |
| Trouve Medtrack Ltd | Information & communication | 2025 |
| Troy LEE Designs Ltd | Wholesale & retail | 2020 |
| True Blue GAS Services Limited | Construction | 2007 |
| True Wood Grills Limited | Manufacturing | 2015 |
| Truevale Care Ltd | Administrative & support | 2019 |
| Trustline Care Ltd | Other services | 2014 |
| Trustmark Care Limited | Administrative & support | 2022 |
| TS Business Limited | Transport & logistics | 2020 |
| Tsang FC Portsmouth Limited | Hospitality | 2019 |
| TSH Investments Ltd | Real estate | 2024 |
| Tssm Perpetual Ltd | Professional & scientific | 2023 |
| Tsvm Furniture Ltd | Manufacturing | 2024 |
| TT Custom Motorcycles Limited | Wholesale & retail | 2018 |
| TT Portsmouth LLP | | 2025 |
| TTB Commercial Ltd | Real estate | 2026 |
| Tudor Carpets Limited | Wholesale & retail | 1980 |
| Tudor Court (Cosham) RTM Company Limited | Households | 2020 |
| Tudor Court Regal Close Limited | Households | 1995 |
| Tudor Homes (Sussex) Limited | Construction | 2003 |
| Tuesday Sunshine Limited | Professional & scientific | 2025 |
| Tuff Company Ltd | Wholesale & retail | 2016 |
| Turkish Hair Designer Ltd | Other services | 2024 |
| Turkish Line Ltd | Other services | 2021 |
| Turkish Mediterranean Restaurant Ltd | Hospitality | 2025 |
| Turnbull Assets Limited | Real estate | 2020 |
| Turner Young LLP | | 2010 |
| Turning Tides Portsmouth CIC | Professional & scientific | 2022 |
| Turnkey Concepts Limited | Administrative & support | 2014 |
| Turnkey Network Solutions Limited | Administrative & support | 2008 |
| Turnoak Properties Limited | Financial services | 1997 |
| Turnstone Mortgages Ltd | Financial services | 2020 |
| Turnwood Developments Ltd | Construction | 2026 |
| Turnwood Holdings Ltd | Administrative & support | 2022 |
| Tutortastic Limited | Education | 2015 |
| TW Accountancy Services Limited | Professional & scientific | 2012 |
| TW Compliance Limited | Professional & scientific | 2024 |
| TW Decorating Ltd | Construction | 2026 |
| TW Truck Ltd | Construction | 2015 |
| TWC Construction Ltd | Construction | 2023 |
| TWC Consultants Ltd | Professional & scientific | 2018 |
| TWC Group Limited | Administrative & support | 2015 |
| TWD Consultancy Limited | Professional & scientific | 2019 |
| Twenty Seven Eight Investments Ltd | Real estate | 2021 |
| TWF Building Services Limited | Construction | 2016 |
| Twin Forts Property Group Ltd | Financial services | 2025 |
| Twin Waters Limited | Real estate | 2024 |
| Twinhearts Healthcare Ltd | Health & social care | 2023 |