| T Lawrence Rental Ltd | Real estate | 2026 |
| T M a Media Marketing Limited | Information & communication | 2019 |
| T R Rigging Maintenance Limited | Information & communication | 2007 |
| T&B Construct Limited | Construction | 2021 |
| T&P Hitchin Limited | Real estate | 2024 |
| T. a . Taylor Limited | Manufacturing | 2002 |
| T.I.A BEE Products (UK) Ltd | Wholesale & retail | 2019 |
| T.W.G. Tiling Ltd | Construction | 2019 |
| T1D Racing Limited | Arts & recreation | 2025 |
| T2D Consulting Limited | Administrative & support | 2008 |
| T2D2 Consulting Limited | Administrative & support | 2023 |
| T50 Software Limited | Information & communication | 2008 |
| TA Retreats Ltd | Hospitality | 2023 |
| Tachyon Research Ltd | Professional & scientific | 2019 |
| Tadayon Consulting Limited | Professional & scientific | 2007 |
| TAE Consulting Limited | Information & communication | 2015 |
| Taeg Limited | Professional & scientific | 2016 |
| Tail ME More Ltd | Other services | 2019 |
| Take Time Saunas Ltd | Health & social care | 2025 |
| Taking Action Ltd | Administrative & support | 2015 |
| Talentcoach Limited | Information & communication | 2026 |
| Talents (Hitchin) Limited | Other services | 2012 |
| Taliesin Carpentry Limited | Manufacturing | 2025 |
| TAM Health Advisory Limited | Education | 2026 |
| Tamburello Property Limited | Real estate | 2026 |
| Tamburello Property Management Limited | Real estate | 2023 |
| Tamsyn Consulting Ltd | Administrative & support | 2015 |
| Tandem Financial Ltd | Financial services | 2015 |
| Tandem Financial Planning Ltd | Financial services | 2015 |
| Tangent Synergy Limited | Administrative & support | 2009 |
| Tangram Technology Limited | Professional & scientific | 1996 |
| Tanoshi Taste Ltd | Hospitality | 2024 |
| Tantallon Management Limited | Administrative & support | 2014 |
| Tara James Consulting Ltd | Professional & scientific | 2022 |
| TAS Reachout Physiotherapy Service Ltd | Health & social care | 2024 |
| Tasheel Technologies Ltd | Information & communication | 2021 |
| Tauro Properties Ltd | Real estate | 2024 |
| Taxecute Limited | Professional & scientific | 2025 |
| Taylor Barnett Limited | Construction | 2026 |
| Taylor HR Solutions Limited | Professional & scientific | 2007 |
| Taylor Page Limited | Transport & logistics | 2020 |
| Taylourgeorgecarpentry Ltd | Construction | 2026 |
| Taymount Clinic Limited | Health & social care | 2019 |
| Taymount Holdings Limited | Health & social care | 2015 |
| Taymount Limited | Manufacturing | 2003 |
| TB Electrical Herts Ltd | Construction | 2025 |
| Tcuk Intl. Limited | Transport & logistics | 2022 |
| TD Apex Holdings Limited | Financial services | 2025 |
| TD Health Tech Limited | Information & communication | 2026 |
| Teachers Together Ltd | Administrative & support | 2020 |
| TEC Electrical Group Limited | Construction | 2025 |
| TEC-2000 Ltd | Wholesale & retail | 2002 |
| Tech People UK Limited | Administrative & support | 2009 |
| Technology Direct Systems Limited | Wholesale & retail | 2009 |
| Technology Resourcing Limited | Administrative & support | 1997 |
| Techreline Limited | Construction | 2012 |
| Tecserv IT Services Ltd | Information & communication | 2023 |
| Teegra Ltd | Administrative & support | 2015 |
| Teeming Limited | Professional & scientific | 2004 |
| Tejo Consulting and Services Ltd | Health & social care | 2025 |
| Teke Programme Solutions Limited | Professional & scientific | 2024 |
| Tele - CUE Limited | Manufacturing | 1985 |
| Telecom Alliance Ltd | Wholesale & retail | 1998 |
| Telecue International Limited | Financial services | 1986 |
| Telesheds Limited | Manufacturing | 2001 |
| Teresa Lazzara Consulting Limited | Professional & scientific | 2026 |
| Terre Initiative Ltd | Real estate | 1998 |
| Terrell & Dunlop Limited | Other services | 2019 |
| Terry Green Limited | Information & communication | 2018 |
| Tesni Consulting Limited | Professional & scientific | 2022 |
| Tessa Campbell Fraser Sculptor Limited | Arts & recreation | 2016 |
| TFE Trading Ltd | Real estate | 2020 |
| TFZ Estates Ltd | Real estate | 2025 |
| TGA Marketing & Design Ltd | Administrative & support | 2007 |
| TGR Developers Ltd | Construction | 2019 |
| Thai Food Direct Ltd | Wholesale & retail | 2018 |
| Thai Food Store Ltd | Wholesale & retail | 2021 |
| Thai LAO Kitchen Take Away Limited | Hospitality | 2019 |
| That Accountant Ltd | Professional & scientific | 2024 |
| That Moment CIC | Education | 2025 |
| THE A&R Awards Ltd | Arts & recreation | 2016 |
| THE App Geeks Ltd | Information & communication | 2012 |
| THE Art Harbour CIC | Health & social care | 2025 |
| THE Aspens (Wymondley Road) Limited | Real estate | 2013 |
| THE Balloon Academy Limited | Arts & recreation | 2022 |
| THE Barnbeth Trust | Professional & scientific | 2010 |
| THE Battle of Britain Locomotive Society | Other services | 1988 |
| THE Beacon Solutions Group Ltd | Manufacturing | 2009 |
| THE Bear and the Bubble Ltd | Hospitality | 2017 |
| THE Beeches Management Company (Hemel Hempstead) Limited | Households | 1996 |
| THE Beechlea Luton Limited Liability Partnership | | 2004 |
| THE Best Party Limited | Arts & recreation | 2023 |
| THE Big Yellow Duck Ltd | Extraterritorial | 2024 |
| THE Blossom Grove Flower Farm Ltd | Agriculture & fishing | 2019 |
| THE Blue Pearl Granite Company Limited | Manufacturing | 2006 |
| THE Bookkeeping Department LLP | | 2020 |
| THE Bridal Apartment Limited | Wholesale & retail | 2021 |
| THE Broadcast Bridge Limited | Extraterritorial | 2014 |
| THE Bucks Head Community Hub CIC | Hospitality | 2026 |
| THE Bucks Head Little Wymondley Ltd | Hospitality | 2025 |