| THE Hill Family Property Limited | Real estate | 2017 |
| THE Hops & Slops PUB Co Ltd | Hospitality | 2010 |
| THE Hospitality Reserve Ltd | Information & communication | 2026 |
| THE Huntsman Group Limited | Administrative & support | 2015 |
| THE INK Studio Ltd | Wholesale & retail | 2026 |
| THE Institute of Public Rights of Way and Access Management Limited | Other services | 2000 |
| THE Insurance Store Limited | Financial services | 2004 |
| THE JAM Talent Limited | Administrative & support | 2020 |
| THE JHH Group Ltd | Financial services | 2025 |
| THE Juice Program Ltd | Wholesale & retail | 2019 |
| THE Kitchen Front LP | | 2020 |
| THE Law Student Support Project C.I.C. | Education | 2018 |
| THE Little Square Gallery Limited | Wholesale & retail | 2013 |
| THE Malta Harpenden Ltd | Hospitality | 2018 |
| THE Match House Limited | Other services | 2026 |
| THE Meadway Court Management Company (Dunstable) Limited | Households | 1991 |
| THE Meating Room (Harpenden) Ltd | Hospitality | 2022 |
| THE Naked Film Co. Ltd | Information & communication | 2026 |
| THE Parmar Family LLP | | 2023 |
| THE People Agenda Limited | Administrative & support | 2025 |
| THE Prentice and Seabright Cups Limited | Arts & recreation | 2022 |
| THE Project at Home Limited | Professional & scientific | 2020 |
| THE Project Box (UK) Limited | Professional & scientific | 2014 |
| THE Real Escape Plan Limited | Professional & scientific | 2017 |
| THE Romford Bull Limited | Arts & recreation | 2021 |
| THE Sharper Edge Limited | Wholesale & retail | 1998 |
| THE Skin Club Clinic Limited | Other services | 2025 |
| THE Small Removal Co. Limited | Transport & logistics | 2000 |
| THE Solar Centre Ltd | Wholesale & retail | 2006 |
| THE Spinney (West Common) Limited | Households | 1995 |
| THE Story Frog Limited | Education | 2017 |
| THE Student Office Limited | Education | 2011 |
| THE Trouser Company Limited | Other services | 2010 |
| THE Vacations Group Limited | Administrative & support | 2002 |
| THE Vegetable Doctor Limited | Hospitality | 2020 |
| THE Vine Cellar Ltd | Wholesale & retail | 2020 |
| THE Weir Nursing Home Ltd | Administrative & support | 1995 |
| THE White House Developments (Boxmoor) Limited | Real estate | 2017 |
| The-Fc Ltd | Arts & recreation | 2023 |
| Thedermacompany Limited | Wholesale & retail | 2001 |
| Thenineteenth Ltd | Construction | 2026 |
| Thesunandmoon Ltd | Real estate | 2022 |
| Think Connect Change Ltd | Administrative & support | 2013 |
| Thinkbox India Limited | Real estate | 2024 |
| Third Chiltern Park Management Limited | Households | 1977 |
| This IS Software Ltd | Information & communication | 2024 |
| Thorburn Developments Ltd | Construction | 2020 |
| Thornhill Scott Limited | Professional & scientific | 1993 |
| Threadshed Limited | Wholesale & retail | 2025 |
| Three Hammers Limited | Real estate | 2026 |
| Threeps Investments Ltd | Transport & logistics | 2002 |
| Thriving-Hopes CIC | Education | 2025 |
| Throwley Services Ltd | Administrative & support | 2019 |
| Tian FU Accommodation Limited | Administrative & support | 2009 |
| Tian FU Travel Limited | Administrative & support | 2012 |
| Tickl Ltd | Information & communication | 2020 |
| Tier 1 Security Limited | Professional & scientific | 2020 |
| Tihtc Limited | Professional & scientific | 2005 |
| Tilecare Ltd | Administrative & support | 2010 |
| TIM M Barlow Limited | Professional & scientific | 2024 |
| Timac Agro UK Limited | Administrative & support | 2009 |
| Times Capital Wealth Management Ltd | Professional & scientific | 2018 |
| Timezoneteam Ltd | Information & communication | 2018 |
| Tiryaki Financial Consulting Ltd | Hospitality | 2020 |
| TIS Finance Ltd | Financial services | 2012 |
| Tisdall Financial Consultants Ltd | Professional & scientific | 2024 |
| TJ Tutors Ltd | Education | 2025 |
| TNR Construction Limited | Manufacturing | 2021 |
| Toastielicious Ltd | Hospitality | 2022 |
| Tofino HS Limited | Professional & scientific | 2012 |
| Tohar PAY Limited | Financial services | 2024 |
| Tokyo Choice Ltd | Hospitality | 2026 |
| TOM Lewis Limited | Arts & recreation | 2011 |
| Tombec Consulting Limited | Professional & scientific | 2021 |
| Tootgarook Ltd | Professional & scientific | 2016 |
| Top Bathrooms (Flitwick) Ltd | Households | 2010 |
| Topkins Healthcare Ltd | Wholesale & retail | 2010 |
| Torrona Ltd | Information & communication | 2024 |
| Total Flow Limited | Professional & scientific | 2006 |
| Total Jobs Solution Ltd | Water & waste | 2023 |
| Total Looks Ltd | Wholesale & retail | 2012 |
| Totalcustomuk Limited | Construction | 2018 |
| Townsend Risk Services Limited | Professional & scientific | 2012 |
| TP Health and Fitness Ltd | Arts & recreation | 2024 |
| Tpog Estates Limited | Hospitality | 2016 |
| Track Sports Limited | Arts & recreation | 2025 |
| Tradewerx Limited | Wholesale & retail | 2021 |
| Trading Service Sports Limited | Administrative & support | 2024 |
| Trafalgar Plant Hire Ltd | Administrative & support | 2012 |
| Training U IT Ltd | Education | 2008 |
| Trans Hair Limited | Professional & scientific | 2000 |
| Transfer Pricing Publications Ltd | Information & communication | 2023 |
| Transparent Paper UK Ltd | Wholesale & retail | 2020 |
| Travel Four Seasons (Harpenden) Limited | Administrative & support | 2018 |
| Treadgold Ltd | Hospitality | 2017 |
| Treeline & Groundwork Services Ltd | Administrative & support | 2025 |
| Trend Plus Bookkeeping Ltd | Professional & scientific | 2021 |
| Trials Addict Limited | Wholesale & retail | 2012 |
| Triangle Property Developments Limited | Construction | 2015 |
| Tributary Creek Ltd | Real estate | 2021 |