| Total Assist Locums Limited | Administrative & support | 2005 |
| Total Assist Nursing Limited | Administrative & support | 2013 |
| Total Assist Private Care Limited | Administrative & support | 2004 |
| Total Assist Property Limited | Real estate | 2025 |
| Total Assist Recruitment (UK) Ltd | Health & social care | 2006 |
| Total Assist Recruitment Limited | Administrative & support | 1999 |
| Total Business Solution Ltd | Extraterritorial | 2009 |
| Total Education Group Limited | Administrative & support | 2008 |
| Total Money Limited | Financial services | 2012 |
| Totally Sporty Limited | Information & communication | 2009 |
| Touch Tax Ltd | Professional & scientific | 2016 |
| Tougo UK Limited | Financial services | 2026 |
| Towerful Ltd | Professional & scientific | 2024 |
| Towfiq Developments Ltd | Real estate | 2022 |
| Town Wall Place Limited | Households | 2000 |
| Tozer Labs Ltd | Information & communication | 2022 |
| Tpac NDT UK Ltd | Information & communication | 2022 |
| Trace Surveys Limited | Professional & scientific | 2010 |
| Track Bounty Limited | Information & communication | 2026 |
| Tradecraft Building Products Limited | Extraterritorial | 2017 |
| Tradesmans Apps Ltd | Information & communication | 2018 |
| Trading Card App Ltd | Information & communication | 2024 |
| Tradix Solutions Ltd | Wholesale & retail | 2026 |
| Tradsco (U.K.) Limited | Real estate | 1986 |
| Training Construction Services Limited | Construction | 2019 |
| Tran Studios Ltd | Other services | 2025 |
| Transglobal UK Limited | Information & communication | 2003 |
| Transiqo Ltd | Administrative & support | 2025 |
| Transmec Services Ltd | Professional & scientific | 2019 |
| Travel Company Tracker Ltd | Information & communication | 2023 |
| Treacle PR Ltd | Professional & scientific | 2015 |
| Treasure Group Limited | Professional & scientific | 2015 |
| Treetop Architects Ltd | Professional & scientific | 2024 |
| Trendy Brunch Limited | Hospitality | 2023 |
| Tres Maria Palma Ltd | Real estate | 2023 |
| Tresata Ltd | Information & communication | 2019 |
| Tribemedia Group Ltd | Information & communication | 2026 |
| Tricor Construction Limited | Professional & scientific | 2016 |
| Tridia Prod UK Limited | Arts & recreation | 2012 |
| Trillium Solutions Ltd | Professional & scientific | 2018 |
| Trinity Fields (Dartford) Management Limited | Households | 2003 |
| Trio Project and Commercial Management Ltd | Construction | 2013 |
| Trio Property Investment Limited | Financial services | 2013 |
| Trishul Consulting Limited | Construction | 2021 |
| Trivalue Limited | Information & communication | 2025 |
| Trivisio Limited | Financial services | 2018 |
| Trivium Partners Ltd | Administrative & support | 2025 |
| Truck Monkey Film Services Ltd | Information & communication | 2026 |
| Truckout Limited | Households | 1980 |
| Trueblue Nurses UK Ltd | Health & social care | 2012 |
| Trueblue Ventures Ltd | Real estate | 2017 |
| Trust a BRO Limited | Other services | 2024 |
| Trust Rubber Latex UK Ltd | Wholesale & retail | 2018 |
| Trusted Autos Ltd | Wholesale & retail | 2026 |
| Trusted Tech Alliance | Information & communication | 2026 |
| Truter Dojo Limited | Information & communication | 2022 |
| Truth in Science | Education | 2005 |
| Trutravels Limited | Administrative & support | 2012 |
| Tsflefkaf Ltd | Information & communication | 2013 |
| TSL TIB Limited | Construction | 2003 |
| TST Investment Ltd | Professional & scientific | 2024 |
| Tsunami Audio Ltd | Professional & scientific | 2025 |
| Tsunami Auto Ltd | Professional & scientific | 2025 |
| TSV Properties Limited | Real estate | 2014 |
| Ttny Consulting Limited | Professional & scientific | 2016 |
| Tucker & Partners Limited | Professional & scientific | 1999 |
| Tudor DRY Cleaning Services Limited | Other services | 2008 |
| Tuff Tooth Ltd | Manufacturing | 2024 |
| Tuffenmark Ltd | Wholesale & retail | 2014 |
| Tufton Services Limited | Administrative & support | 1985 |
| Tulip Hyacinth Ltd | Wholesale & retail | 2023 |
| Tulip Landscapes London Limited | Administrative & support | 2014 |
| Tuppence and Crumble Ltd | Wholesale & retail | 1991 |
| Turnham Ventures Ltd | Professional & scientific | 2024 |
| Turonian Drilling Limited | Professional & scientific | 2026 |
| Turquoise Investment and Capital Ltd | Real estate | 2019 |
| Turquoise Marine Services Limited | Mining & quarrying | 2020 |
| Tussock Peak Consulting Limited | Information & communication | 2016 |
| Tutor Stream Ltd | Education | 2019 |
| Tutorlyworld Limited | Education | 2026 |
| TVZ Media Services Limited | Information & communication | 2024 |
| TW Aesthetics Ltd | Health & social care | 2021 |
| TW Holdings Limited | Real estate | 2006 |
| TW11 Digital Ltd | Professional & scientific | 2024 |
| TW11 News Limited | Administrative & support | 2025 |
| TW3 Building Specialists Limited | Construction | 2020 |
| Twende Productions Limited | Administrative & support | 2021 |
| TWENTY5UP Ltd | Administrative & support | 2021 |
| Twin International Ltd | Wholesale & retail | 2015 |
| Twin Oaks Decision Consulting Ltd | Information & communication | 2023 |
| Two Fingers TV Limited | Information & communication | 2006 |
| Two Mugs Coffee and Matcha Ltd | Hospitality | 2026 |
| Two Potatoes Limited | Hospitality | 2024 |
| Twopointnine Limited | Arts & recreation | 2000 |
| Twopointnine Publishing Ltd | Information & communication | 2003 |
| Tyler Enterprises Limited | Financial services | 2017 |
| Tyndall Maingay Limited | Financial services | 2025 |
| TZP Properties Limited | Real estate | 2022 |
| U Tea CHA Swiss Cottage Limited | Education | 2016 |
| U&K Foods Ltd | Hospitality | 2020 |