| Thesamsons Limited | Education | 2007 |
| Thobani Investments Limited | Health & social care | 2008 |
| Thomas Gibson Fine Art Limited | Wholesale & retail | 1970 |
| Thorley Community Centre Limited | Real estate | 1994 |
| Thornfield Garages Limited | Administrative & support | 1999 |
| Thornton Electrical (London) Limited | Construction | 2006 |
| Three Spires Reporting Ltd | Health & social care | 2022 |
| Tiara Blackline Ltd | Transport & logistics | 2026 |
| Tiber Ludwig Limited | Real estate | 2000 |
| TIC Consulting Limited | Professional & scientific | 2006 |
| Ticktock Fit Ltd | Arts & recreation | 2024 |
| Timberford Estates Limited | Real estate | 2001 |
| Tithe Barn Management Limited | Households | 1986 |
| TJM Property Maintenance Services Limited | Construction | 2006 |
| TKR Planning Consultants Limited | Other services | 2018 |
| Tlspu Limited | Information & communication | 2026 |
| TMC Property Developments Ltd | Real estate | 2025 |
| TMC Technology UK Co., Ltd. | Wholesale & retail | 1992 |
| TOG Consulting Limited | Professional & scientific | 2004 |
| Tolmers Construction Limited | Construction | 2005 |
| Toltec Ltd | Professional & scientific | 2024 |
| TOM Hagan (UK) Limited | Wholesale & retail | 2000 |
| Tomkat Management Limited | Households | 2006 |
| Tonic Facilitation Limited | Professional & scientific | 2003 |
| Top Marks Cleaning Services Limited | Administrative & support | 2006 |
| Top Notch Limited | Wholesale & retail | 1998 |
| Topfolk.Com Limited | Professional & scientific | 2001 |
| Topgear Autocentre Limited | Extraterritorial | 2004 |
| Topgold Limited | Real estate | 2001 |
| Toptek Talent Ltd | Administrative & support | 2020 |
| Toro U.K. Limited | Manufacturing | 2004 |
| Tosun Scaffolding Limited | Construction | 2003 |
| Total Computer Supplies Limited | Transport & logistics | 1994 |
| Total Design Consultancy Services LLP | | 2006 |
| Total Joinery Solutions Limited | Construction | 2005 |
| Tote Maintenance Limited | Construction | 2021 |
| Toto Footwear Limited | Wholesale & retail | 1991 |
| Totteridge Developments Limited | Construction | 2004 |
| Toucan Gifts Limited | Wholesale & retail | 2013 |
| Townfield Projects Limited | Administrative & support | 1999 |
| Towns-End Double Glazing Limited | Construction | 2001 |
| Toy Balloons Ltd | Wholesale & retail | 2026 |
| Trader Mick Limited | Wholesale & retail | 2002 |
| Trafalgar Corporation Limited | Administrative & support | 1988 |
| Traffordcity Snowcentre Limited | Administrative & support | 2018 |
| Transfer Pricing Solutions Limited | Professional & scientific | 2003 |
| Transport Bookman Publications Limited | Information & communication | 1965 |
| Trantek Traders Limited | Professional & scientific | 1992 |
| TRE Advisory Limited | Wholesale & retail | 2025 |
| Treacy Surfacing Limited | Construction | 1972 |
| Trek Removals Limited | Transport & logistics | 2002 |
| Trendremote Projects Limited | Construction | 1993 |
| Trevor Square Garden Management Company Limited | Real estate | 1990 |
| Treyan Pharma Limited | Wholesale & retail | 2025 |
| Trident Applications Limited | | 1990 |
| Trinity Developers Limited | Real estate | 2006 |
| Trioptics UK Limited | Extraterritorial | 1997 |
| Tropical Marine Centre Group (2021) Ltd | Wholesale & retail | 2021 |
| True Signal Audio Europe Ltd | Manufacturing | 2023 |
| Truehorizon Consulting Ltd | Professional & scientific | 2025 |
| Trust Matters Financial Services Limited | Financial services | 1989 |
| Trust Matters Limited | Financial services | 1994 |
| TS Cribs Ltd | Real estate | 2021 |
| TUN Abdul Razak Research Centre | Professional & scientific | 1938 |
| Tune Property Services Limited | Wholesale & retail | 2001 |
| Tunfield Cleaning & Maintenance Ltd. | Administrative & support | 2002 |
| Turneround UK Limited | Other services | 2000 |
| Turpins Ride Management Committee Limited | Households | 1993 |
| TV Formats Limited | Information & communication | 2003 |
| TV News London Limited | Information & communication | 1986 |
| TVA Technology Limited | Wholesale & retail | 2015 |
| Twilight Zone Engineering Limited | Wholesale & retail | 1992 |
| Twins Services Limited | Education | 2007 |
| TWL Property Leasehold Ltd | Real estate | 2025 |
| Two's Company Design Studios Limited | Arts & recreation | 1986 |
| Tyannamaliya-Ajaneecraftstore Ltd | Wholesale & retail | 2025 |
| TYE Design Limited | Administrative & support | 2006 |
| Tyvin Estates Limited | Construction | 1968 |
| U S Tractors Limited | Transport & logistics | 2007 |
| U&U Civil Engineering Ltd | Construction | 2022 |
| U.K. Marine Parts Limited | Administrative & support | 1996 |
| UC Associates Worldwide Limited | Administrative & support | 2006 |
| UCS Accountancy Services Limited | Professional & scientific | 2001 |
| UGO Foods Group Limited | Manufacturing | 1938 |
| Uk-Euro Printing Limited | Extraterritorial | 2003 |
| Ukhr.Com Limited | Professional & scientific | 2001 |
| Ultimate Financial Solutions Limited | Financial services | 2003 |
| Ultimate Wedding Venues Limited | Administrative & support | 2002 |
| Unada Limited | Information & communication | 2010 |
| Unicorn Painting Contractors Limited | Construction | 1997 |
| Unidrape Blinds Ltd | Administrative & support | 2005 |
| United Kingdom Tang SOO DO Federation MOO DUK Kwan Limited | Professional & scientific | 1996 |
| University Close Management Limited | Households | 1981 |
| Universitybus Limited | Transport & logistics | 1989 |
| Univirtual Limited | Information & communication | 2001 |
| Urbanphase Residents Management Limited | Households | 1988 |
| Utopian Build Ltd | Construction | 2020 |
| UV Consultancy Services Ltd | Information & communication | 2008 |
| V Star Business Services Ltd | Professional & scientific | 1997 |
| V-Twin Cafe Ltd | Hospitality | 2025 |