| Thrivereigate Limited | Other services | 2019 |
| Thurlowe Clarke Limited | Financial services | 1978 |
| Tictrac Limited | Information & communication | 2010 |
| Tidy Tours Ltd | Administrative & support | 2024 |
| Tiger Sand Shark Films Ltd | Arts & recreation | 2023 |
| Time Save Cars Ltd | Transport & logistics | 2019 |
| Tinotenda Limited | Administrative & support | 2010 |
| Tiralytix Limited | Information & communication | 2023 |
| Tiver Construction Limited | Construction | 2025 |
| TJS Services Limited | Construction | 1998 |
| TK&PC2 Limited | Financial services | 2023 |
| Tkpc 1 Limited | Financial services | 2017 |
| TKS Global Limited | Wholesale & retail | 2011 |
| TKS International Ltd | Wholesale & retail | 2022 |
| TL Jackson Private Practice Ltd | Health & social care | 2011 |
| TM Market Solutions Limited | Professional & scientific | 2013 |
| TMC Sussex Limited | Other services | 2018 |
| TNK Developments Limited | Construction | 2025 |
| TNR Nails Ltd | Other services | 2025 |
| Toby Risk Consulting Ltd | Information & communication | 2025 |
| Tojo Corporation Limited | Financial services | 2025 |
| Tolworth Fencing Company Limited | Construction | 2003 |
| Tolworth Fencing Supplies Ltd | Wholesale & retail | 2020 |
| TOM Collins Production Ltd | Administrative & support | 2025 |
| TOM Phillips Ltd | Hospitality | 2020 |
| Tomas Acquisitions Limited | Extraterritorial | 2018 |
| Tongda Distribution Ltd | Transport & logistics | 2019 |
| Tonic Creative Business Partners Ltd | Administrative & support | 2016 |
| Tooley Developments LLP | | 2010 |
| Top Blue Limited | Manufacturing | 2014 |
| Top Hair Fashion Limited | Wholesale & retail | 2013 |
| Toptier Consulting Limited | Professional & scientific | 2004 |
| Toreal Limited | Administrative & support | 2011 |
| Tourbillon Real Estates Ltd | Real estate | 2025 |
| Towelwizz Ltd | Wholesale & retail | 2014 |
| Towers Perrin (UK) Trustee Company Limited | Professional & scientific | 1985 |
| Towers Watson Global 2 Limited | Professional & scientific | 2013 |
| Towers Watson Global 3 Limited | Professional & scientific | 2013 |
| Towers Watson Global Holdings Limited | Professional & scientific | 2012 |
| Towers Watson Investment Management Limited | Financial services | 2005 |
| Towers Watson Limited | Professional & scientific | 2005 |
| Towers Watson Pension Scheme Trustees Limited | Extraterritorial | 2010 |
| Towers Watson Software Limited | Information & communication | 1997 |
| Tpayne Consulting Limited | Information & communication | 2015 |
| Tprc Ltd | Construction | 2017 |
| Tracemaps Limited | Manufacturing | 2016 |
| Track & Drive Ltd | Administrative & support | 2025 |
| Tradefc Limited | Financial services | 2015 |
| Trafficwatch Vision Ltd | Professional & scientific | 2022 |
| Train AID Limited | Education | 2009 |
| Trainy Days Limited | Information & communication | 2006 |
| Tramore Property Management Limited | Households | 2021 |
| Transformtech Consulting Ltd | Professional & scientific | 2016 |
| Transport Auctions of London Ltd | Wholesale & retail | 2015 |
| Travel Trade Exchange Limited | Professional & scientific | 2023 |
| Treemount Ltd | Health & social care | 2017 |
| Treemount Properties Ltd | Real estate | 2026 |
| Tremmorr Ltd | Manufacturing | 2021 |
| Tresan Roofing Limited | Construction | 2023 |
| Triple One Holdings Limited | Professional & scientific | 2019 |
| Trisource Gourmet Limited | Manufacturing | 2025 |
| Triumphage Limited | Real estate | 2014 |
| Tropical Commodity Analysts Limited | Professional & scientific | 2010 |
| Truth Marketing Ltd | Professional & scientific | 2011 |
| Tryway Properties Limited | Construction | 1997 |
| TSF Companies Ltd | Professional & scientific | 2022 |
| Tsvetelina Ltd | Manufacturing | 2017 |
| TT Decorating Services Ltd | Construction | 2019 |
| TTB Media Ltd | Other services | 2012 |
| Ttechnology Ltd | Wholesale & retail | 2019 |
| Ttspr Limited | Other services | 2017 |
| Tuco Band Ltd | Information & communication | 2026 |
| Tudor Capital Holding Ltd | Financial services | 2026 |
| Tudor Capital Properties Ltd | Real estate | 2026 |
| Turquoise Internet Limited | Manufacturing | 2010 |
| Tvfilm Limited | Information & communication | 2004 |
| TW Structures Ltd | Construction | 2026 |
| TW26 Ltd | Financial services | 2024 |
| Twenty 8 Management Limited | Hospitality | 2004 |
| Twenty TEN Productions Ltd | Information & communication | 2022 |
| Twenty Two Collective Limited | Professional & scientific | 2023 |
| Twickenham Training Limited | Education | 2006 |
| Twin Dynasty Ltd | Hospitality | 2011 |
| TY Arran Limited | Real estate | 2016 |
| TY Newyddion Ltd | Real estate | 2021 |
| Tyche Developments Ltd | Construction | 2016 |
| U-Blox UK Ltd. | Professional & scientific | 2007 |
| Ufonic Ltd | Manufacturing | 2021 |
| UK Macro Meals Limited | Manufacturing | 2016 |
| Ukagileai Ltd | Professional & scientific | 2026 |
| Uknetpayroll.Com Limited | Professional & scientific | 2013 |
| ULL Property Limited | Real estate | 2020 |
| Ultimate Fire Protection Limited | Public administration | 2014 |
| Umbrella Construction and Investment Limited | Construction | 2019 |
| Unfold Wellness Limited | Other services | 2026 |
| Unilecithin UK Ltd | Manufacturing | 2023 |
| Unity X Ltd | Administrative & support | 2022 |
| Unlimited RAO Limited | Agriculture & fishing | 2020 |
| Unusual Exhibitions Ltd | Administrative & support | 2016 |
| Upright Developments (South East) Ltd | Construction | 2022 |