| TKM Engineering Limited | Manufacturing | 2024 |
| TLF Asset Services Ltd | Administrative & support | 2023 |
| TLW Assets and Holdings Ltd | Administrative & support | 2020 |
| TLW Plumbing and Heating Ltd | Construction | 2025 |
| TMD Commercial Management Ltd | Professional & scientific | 2018 |
| TMT Computer Systems Limited | Information & communication | 1998 |
| Tnss Limited | Information & communication | 2026 |
| Toby Thomson Wealth Management Limited | Financial services | 2018 |
| TOM Garnett Scaffolding (Hire & Sales) Limited | Administrative & support | 2019 |
| TOM Garnett Scaffolding Limited | Administrative & support | 2015 |
| Tomorrows World Recycling UK Ltd | Transport & logistics | 2014 |
| Tone SIX Software Limited | Information & communication | 2009 |
| Tony Briscoe Photography Limited | Professional & scientific | 2002 |
| Tools 4 U Ltd | Wholesale & retail | 2025 |
| Tools Number 1 UK Ltd | Wholesale & retail | 2025 |
| Top Banana Supplies Limited | Other services | 2020 |
| Top DOC Education Ltd | Education | 2017 |
| Top Shelf Bars Ltd | Hospitality | 2025 |
| Topbamboo Limited | Wholesale & retail | 2020 |
| Torchwood Solutions Limited | Financial services | 2015 |
| Total Data Management Limited | Administrative & support | 2007 |
| Total Sealant Services LLP | | 2017 |
| Total Spraying Limited | Wholesale & retail | 2012 |
| Totallybeads Ltd | Manufacturing | 2006 |
| Totes Isotoner (UK) Limited | Wholesale & retail | 1980 |
| Touch of Class (Original) Ltd | Other services | 2006 |
| Tourish London Limited | Water & waste | 2021 |
| Tower B M Limited | Construction | 2014 |
| Townshend Consultancy Services Limited | Real estate | 2023 |
| TP Contracting Limited | Information & communication | 2016 |
| TQ Building Services Ltd | Construction | 2018 |
| Tracked Protection Ltd | Administrative & support | 2026 |
| Trademark Print Consultancy Limited | Manufacturing | 2011 |
| Trafertir (UK) Ltd | Transport & logistics | 1999 |
| Trafertir International Transport Ltd | Transport & logistics | 2014 |
| Trailpoint Limited | Professional & scientific | 2024 |
| Trakt Developments Ltd | Construction | 2024 |
| Travel Tales Holidays Ltd | Hospitality | 2024 |
| Trawick International Ltd | Financial services | 2022 |
| Treadwell Property Holdings Limited | Real estate | 2019 |
| Treharne Consulting Services Ltd | Professional & scientific | 2021 |
| Trevain Lucence Consultancy Limited | Professional & scientific | 2013 |
| Trigem Infotech Limited | Real estate | 2022 |
| Trigg Properties Ltd | Real estate | 2019 |
| Trinity Family Centre Limited | Health & social care | 2006 |
| Triosales Limited | | 1987 |
| Triple M Consulting Ltd | Professional & scientific | 2026 |
| TRL Communications Limited | Construction | 2007 |
| Troika Panel Management and Secretariat Services Limited | Professional & scientific | 2020 |
| Trophyland Limited | Other services | 1978 |
| True Staging Group Limited | Financial services | 2026 |
| True Staging Ltd | Arts & recreation | 2008 |
| True Tile Bathrooms Ltd | Construction | 2025 |
| Trusted Home Solutions Ltd | Construction | 2021 |
| TSM Bing Limited | Arts & recreation | 2024 |
| TST Rail Consultants Ltd | Construction | 2024 |
| TT Optical Solutions Ltd | Information & communication | 2025 |
| Tuckwell Estates Ltd | Households | 2020 |
| Tudor Consulting Group Ltd | Professional & scientific | 2019 |
| Tulip Rentals Limited | Real estate | 2011 |
| Tuppence Holdings Ltd | Professional & scientific | 2017 |
| Turkish Terrace Limited | Hospitality | 2024 |
| Turn 1 Limited | Arts & recreation | 2018 |
| Turnkey Utility Solutions Ltd | Information & communication | 2024 |
| Turtle Flame Limited | Information & communication | 2016 |
| Tuscan Homes Limited | Professional & scientific | 2003 |
| TVC Capital Limited | Financial services | 2018 |
| TVL Finishing Limited | Administrative & support | 2011 |
| TVL Manufacturing Limited | Manufacturing | 1993 |
| Twenty One TEN Consultancy Limited | Information & communication | 2011 |
| Twentytwo Pilates Limited | Extraterritorial | 2024 |
| Twinfit PT Ltd | Education | 2026 |
| TWY Consulting Ltd | Professional & scientific | 2020 |
| TYE Consultancy Ltd | Professional & scientific | 2024 |
| Tyler Mason Consultants Limited | Administrative & support | 2015 |
| Tyler Property Management Ltd | Real estate | 2017 |
| Tyler Security Limited | Administrative & support | 2007 |
| Tyler Specialist Search Dogs Ltd | Administrative & support | 2023 |
| Tylers Auto Parts Ltd | Wholesale & retail | 2019 |
| U Ahmed Limited | Health & social care | 2016 |
| U.K. Media Group Limited | Administrative & support | 2001 |
| UGC Limited | Information & communication | 2019 |
| UK Auto Solutions Limited | Extraterritorial | 2014 |
| UK Media Group (Holdings) Limited | Financial services | 2026 |
| UK Media Limited | Administrative & support | 2013 |
| UK Stage Services Limited | Arts & recreation | 2014 |
| UK Stretch Ceilings Limited | Construction | 2021 |
| UK TA Specialist Limited | Information & communication | 2025 |
| Ultimate Construct Ltd | Construction | 2023 |
| Ultimate Radio Ltd | Information & communication | 2009 |
| Ultras Design Limited | Wholesale & retail | 2024 |
| Underwood Investments (Essex) Ltd | Financial services | 2024 |
| Union Engineering Limited | Professional & scientific | 2006 |
| Unique Body Clinic Wellness Centre Ltd | Other services | 2018 |
| Unique Mortgages Ltd | Financial services | 2020 |
| Uniquory Limited | Wholesale & retail | 2025 |
| Unit Four Colour Specialists Ltd | Other services | 2019 |
| United Scaffolding Ltd | Construction | 2016 |
| United Scaffolding Services Ltd | Construction | 2024 |
| Universal Associate Agency Ltd | Administrative & support | 2020 |