| Thinkova Limited | Information & communication | 2025 |
| Thirst AID IW Ltd | Hospitality | 2026 |
| Thistlegate Estates Ltd | Real estate | 2023 |
| THM Associates Limited | Wholesale & retail | 2023 |
| Thomas & Williams Construction Ltd | Extraterritorial | 2015 |
| Thomas Blake Limited | Real estate | 2010 |
| Thomas Bradley & Co (Wales) Limited | Other services | 2017 |
| Thomas Brothers Group Limited | Agriculture & fishing | 2016 |
| Thomas Brothers Limited | Financial services | 2022 |
| Thomas Evans Limited | Arts & recreation | 2004 |
| Thomas James Evans Ltd | Wholesale & retail | 2026 |
| Thomas Property & Rentals Ltd | Real estate | 2016 |
| Thomas Property Renovations Ltd | Construction | 2024 |
| Thomas Trust Properties Ltd | Real estate | 2024 |
| Thomas Wealth Management Limited | Professional & scientific | 2021 |
| Thomas's & Co Limited | Health & social care | 2022 |
| Thompson's Health Limited | Other services | 2023 |
| Thoresby Developments Limited | Real estate | 1988 |
| Thorne Rainwater Services Limited | Construction | 2026 |
| Thorness House Management Limited | Households | 1999 |
| Thornmanor Limited | Real estate | 1988 |
| Thornwood Estate Management Company Limited | Real estate | 2023 |
| Thornwood Estates IW Limited | Construction | 2018 |
| Thoughtways Ltd | Health & social care | 2010 |
| Three Blackbirds Ltd | Real estate | 2019 |
| Three Plus Ltd | Real estate | 2017 |
| Threefish Aqua Limited | Wholesale & retail | 2019 |
| Thrive Business Academy Limited | Other services | 2024 |
| Thrive Management Solutions Limited | Professional & scientific | 2025 |
| Thrive Psychology Services Ltd. | Education | 2012 |
| Thrivescapeworld Limited | Information & communication | 2025 |
| Throstle Worde Media Ltd | Information & communication | 2024 |
| Thryvon Shield Ltd | Information & communication | 2025 |
| THS HR Services Limited | Administrative & support | 2011 |
| Thunderbolt Productions Ltd | Arts & recreation | 2022 |
| Thunderlaser Limited | Wholesale & retail | 2019 |
| TIA Recycling Limited | Manufacturing | 2022 |
| Tiarafield Holding Limited | Wholesale & retail | 2026 |
| Tibberton Engineering Limited | Other services | 2002 |
| Tickled Trout Ltd | Hospitality | 2023 |
| Tickledom Theatrical Productions Limited | Arts & recreation | 2017 |
| Tidalworx Ltd | Manufacturing | 2024 |
| Tidi Group Limited | Information & communication | 2025 |
| Tidy Cleaning Company Limited | Administrative & support | 2022 |
| Tidy Products Limited | Manufacturing | 2024 |
| TIG Industrial Limited | Wholesale & retail | 2018 |
| Tiger Bay Gifts Ltd | Wholesale & retail | 2011 |
| Tiger Consultancy Services Limited | Professional & scientific | 2009 |
| Tiger EYE Atelier Ltd | Wholesale & retail | 2025 |
| Tigercub Prints Ltd | Wholesale & retail | 2022 |
| Tigeroo Properties Limited | Construction | 2025 |
| Tigmo Limited | Hospitality | 2022 |
| Tile & Stone Flooring Limited | Construction | 2016 |
| Tilley's Holding Company Limited | Financial services | 2022 |
| Tillott Renewable Contracting Ltd | Construction | 2017 |
| TIM Knight Roofing Limited | Construction | 2002 |
| TIM Savage Associates Ltd | Professional & scientific | 2009 |
| TIM Walker TV Ltd | Information & communication | 2012 |
| Timbek Ltd | Construction | 2015 |
| Timber Slate Limited | Construction | 2023 |
| Timberfix UK Limited | Manufacturing | 2024 |
| Time Counselling and Wellbeing Centre Limited | Health & social care | 2019 |
| Timeless Aesthetics Clinic Ltd | Extraterritorial | 2025 |
| Timeless Investment Portfolio Limited | Real estate | 2025 |
| Timoda Ltd | Wholesale & retail | 2023 |
| Timtay & Co Ltd | Real estate | 2025 |
| TIN Shed Theatre Community Interest Company | Administrative & support | 2020 |
| Tina Carter Wellness Ltd | Arts & recreation | 2024 |
| Tinkers ROW Brewery Company Limited | Manufacturing | 2020 |
| Tiny Cat Ltd | Hospitality | 2020 |
| Tiny Rebel Bars Limited | Hospitality | 2021 |
| Tiny Rebel Limited | Manufacturing | 2011 |
| Tiny Rebel Properties Limited | Real estate | 2024 |
| Tiny T'S Ltd | Health & social care | 2026 |
| Tiny Toes Ballet (Cardiff) Limited | Education | 2023 |
| Tiny Toes Ballet Monmouthshire Ltd | Education | 2024 |
| Tiny Tots Premier Childcare Services Limited | Health & social care | 2000 |
| TIR AD Limited | Professional & scientific | 2025 |
| Tisugo Ltd | Construction | 2018 |
| Titan Carpets Limited | Wholesale & retail | 2002 |
| Titus Trans Ltd | Transport & logistics | 2023 |
| Tiverton Doone Limited | Real estate | 2021 |
| TJ Auto Mech Ltd | Wholesale & retail | 2026 |
| TJ Cabs Ltd | Transport & logistics | 2023 |
| TJ Capital Group Limited | Financial services | 2024 |
| TJ Housing Ltd | Real estate | 2020 |
| TJR Financial Planning Ltd | Financial services | 2015 |
| TJS Brand Consultancy Ltd | Information & communication | 2024 |
| TJW Carpentry (IOW) Ltd | Construction | 2023 |
| TKC Healthcare Limited | Health & social care | 2014 |
| TKO Building Contractors Limited | Construction | 2019 |
| TL Electrical (IOW) Ltd | Construction | 2014 |
| TLC Risca Ltd | Hospitality | 2015 |
| TLC Scaffolding Ltd | Construction | 2025 |
| TMJ Building & Maintenance Ltd | Construction | 2026 |
| TMM Retail Ltd | Wholesale & retail | 2024 |
| TMO Creative Ltd | Professional & scientific | 2025 |
| Tmobt Ltd | Professional & scientific | 2025 |
| TMR Cars Limited | Wholesale & retail | 2017 |
| Tmrwartist Ltd | Information & communication | 2026 |