| Transmission Developments Co (GB) Limited | Manufacturing | 1985 |
| Transport AI Solutions Ltd | Information & communication | 2021 |
| Transport Damian Gniazdowski Ltd | Transport & logistics | 2025 |
| Transport Kamil Kapica Ltd | Transport & logistics | 2025 |
| Transport-Plt Ltd | Transport & logistics | 2026 |
| Transportwijko. Ltd | Transport & logistics | 2024 |
| Travalon Property Management Ltd | Real estate | 2022 |
| Travelling Lines Group Ltd | Information & communication | 2018 |
| Travva Ltd | Administrative & support | 2025 |
| TRB Group Holdings Ltd | Financial services | 2025 |
| TRE Figlie Limited | Real estate | 2018 |
| Treacle & Custard Limited | Administrative & support | 2006 |
| Treading Wild Ltd | Wholesale & retail | 2021 |
| Treasured Heritage Limited | Administrative & support | 2025 |
| Treasury Collectables Ltd | Wholesale & retail | 2026 |
| Treats of Nature Limited | Wholesale & retail | 2023 |
| Treble C Auto Services Limited | Wholesale & retail | 2005 |
| Treble Maker Darts Ltd | Wholesale & retail | 2026 |
| Treds Tyres Limited | Transport & logistics | 2004 |
| Tree Hive Limited | Administrative & support | 2022 |
| Treedao Limited | Agriculture & fishing | 2021 |
| Treetop Publishing Limited | Information & communication | 1995 |
| Trelawne Country Park Limited | Hospitality | 2022 |
| Tremel UK Ltd | Financial services | 2023 |
| Trend Developments Limited | Construction | 2002 |
| Trendologyshop Ltd | Wholesale & retail | 2024 |
| Trendologystore Ltd | Other services | 2025 |
| Trendorbit Ltd | Wholesale & retail | 2025 |
| Trendoshopram Limited | Wholesale & retail | 2026 |
| Trent Investigations Ltd | Administrative & support | 2017 |
| Trepmade Limited | | 1982 |
| Tressette Limited | Real estate | 2020 |
| Trevex Holdings Ltd | Financial services | 2020 |
| Trezor Offers Limited | Wholesale & retail | 2025 |
| TRI Catering Equipment Ltd | Wholesale & retail | 2006 |
| Trial of PYX Limited | Professional & scientific | 2021 |
| Triangle Media Limited | Information & communication | 1998 |
| Tribal Talent Ltd | Administrative & support | 2020 |
| Tribune Way Limited | Real estate | 2017 |
| Trick Box Ltd | Education | 2017 |
| Trickett Welding (Poole) Ltd | Manufacturing | 2000 |
| Tricourt Piling and Foundations Ltd | Construction | 2002 |
| Tricuro Ltd | Health & social care | 2015 |
| Tricuro Support Ltd | Health & social care | 2015 |
| Trident Homes Ltd | Construction | 2025 |
| Trident Marine Ltd | Administrative & support | 2008 |
| Trident Media Limited | Information & communication | 2020 |
| Trident Umbrella Limited | Administrative & support | 2023 |
| Trilor Limited | Construction | 2003 |
| Trinity Architects Limited | Professional & scientific | 2000 |
| Trinity Architectural Limited | Professional & scientific | 2000 |
| Trinity Architecture Limited | Professional & scientific | 1996 |
| Trinity Dream Homes Ltd | Real estate | 2023 |
| Trinity Gates Developments Limited | Construction | 2016 |
| Trinity LL Ltd | Health & social care | 2018 |
| Trinity Property Enterprises Limited | Real estate | 2018 |
| Trinus Development Limited | Information & communication | 2024 |
| Triorthagon Ltd | Information & communication | 2025 |
| Triple a Burger Truck Ltd | Hospitality | 2025 |
| Triple INK Warehouse Ltd | Real estate | 2026 |
| Triple Yellow Ltd | Professional & scientific | 2020 |
| Tripledouble Group Ltd | Professional & scientific | 2021 |
| Triplemind Ltd | Wholesale & retail | 2025 |
| Tripleops Limited | Professional & scientific | 2011 |
| Tripolis Games Limited | Information & communication | 2022 |
| Trisam Healthcare Services UK Ltd | Administrative & support | 2019 |
| Trispen Village Store Ltd | Wholesale & retail | 2023 |
| Triumph Land Limited | Health & social care | 2003 |
| Triumph Twin Power Limited | Other services | 2013 |
| Trivanta Services Limited | Wholesale & retail | 2026 |
| Trj-Ed Ltd | Education | 2026 |
| TRK Spice Ltd | Hospitality | 2025 |
| Troika Dorset LLP | | 2016 |
| Troika Wessex Properties Limited | Real estate | 2026 |
| Tropics Cargo UK Limited | Extraterritorial | 2008 |
| Tropika Health UK Ltd | Wholesale & retail | 2026 |
| Trovexa Limited | Wholesale & retail | 2025 |
| Truck 'N' Trolley (UK) LLP | | 2006 |
| True Accountancy Solutions Ltd | Professional & scientific | 2024 |
| True Arrow Limited | Financial services | 2019 |
| True Health Limited | Arts & recreation | 2015 |
| True North Data Governance and Compliance Consultancy Ltd | Professional & scientific | 2026 |
| True North Recruitment Ltd | Administrative & support | 2023 |
| True Power Marine Electrical Services Limited | Manufacturing | 2019 |
| True South Projects Limited | Construction | 2026 |
| Truechef Ltd | Wholesale & retail | 2020 |
| Truly Scrumptious (Dorset) Ltd | Manufacturing | 2012 |
| Trussbuilt (UK) Limited | Manufacturing | 1999 |
| Trust 1 Properties Ltd | Construction | 2026 |
| Trust HR and Recruitment Ltd | Administrative & support | 2021 |
| Trust Private Nursing Ltd | Health & social care | 2026 |
| Trusted Consulting Services Limited | Professional & scientific | 2023 |
| Trusted Wills and Probate (Wessex) Limited | Public administration | 2026 |
| Trustees of the Storewatch.Co.Uk Employee Ownership Trust Limited | Extraterritorial | 2023 |
| Trusthomes Ltd | Real estate | 2018 |
| Trustu Discount Offers Ltd | Wholesale & retail | 2025 |
| Trusty Clean Ltd. | Administrative & support | 2015 |
| Truu Distribution Ltd | Construction | 2025 |
| Truu Ltd | Information & communication | 2015 |
| Truu Tools Ltd | Manufacturing | 2023 |