| TC (East) Partnership LLP | | 2026 |
| TDM Scaffolding Limited | Construction | 2021 |
| Team Building Systems Limited | Administrative & support | 2010 |
| Team Triad Limited | Arts & recreation | 2017 |
| Tebtes Limited | Real estate | 1965 |
| Tech Repairs Letchworth Limited | Other services | 2022 |
| Technical Authoring Services Ltd | Arts & recreation | 2014 |
| Tecs-Uk Ltd | Construction | 2004 |
| Telerad Partners Ltd | Health & social care | 2024 |
| Telsolutions Limited | Information & communication | 2004 |
| Temperton Miller Limited | Professional & scientific | 2003 |
| Templar Regulatory Consulting Limited | Professional & scientific | 2021 |
| Tenhaw Ltd | Information & communication | 2020 |
| Terra Conscious International Ltd | Construction | 2024 |
| Tesoro Wood Works Ltd | Manufacturing | 2023 |
| Testworks Manufacturing Limited | Manufacturing | 2012 |
| Tetherhq Limited | Information & communication | 2025 |
| Tforce Fitness Ltd | Professional & scientific | 2023 |
| Tforce Training Club Ltd | Education | 2023 |
| Tgig Ltd | Other services | 2021 |
| TGJ Bros Braintree Ltd | Hospitality | 2014 |
| TGJ Bros Great Yarmouth Limited | Administrative & support | 2017 |
| Thales Trading Ltd | Information & communication | 2023 |
| THE Altro Foundation Limited | Other services | 2016 |
| THE Altro Group SIP Trustees Limited | Professional & scientific | 1932 |
| THE Arena Tavern Limited | Hospitality | 2000 |
| THE Behavioural Economists Ltd | Professional & scientific | 2025 |
| THE Big Green Bookshop Limited | Wholesale & retail | 2007 |
| THE Build Shop Ltd | Construction | 2016 |
| THE Busy Bee's Projects Limited | Professional & scientific | 2024 |
| THE Cakey Lady Limited | Hospitality | 2019 |
| THE Cat Laboratory Ltd | Wholesale & retail | 2024 |
| THE Change Partners Recruitment Ltd | Administrative & support | 2015 |
| THE Chiswick Calendar CIC | Information & communication | 2017 |
| THE Chiswick Directory Ltd | Information & communication | 2025 |
| THE Christian Bookshop (Letchworth) Limited | Extraterritorial | 2008 |
| THE Cookie Club Limited | Education | 2013 |
| THE Crafty Beer Company Ltd | Wholesale & retail | 2014 |
| THE Crafty Beer Shop - Letchworth Limited | Hospitality | 2016 |
| THE Crescent FP Management Company Limited | Households | 2009 |
| THE Difference Engine Consultants Limited | Information & communication | 2018 |
| THE Doting Carers Ltd | Administrative & support | 2020 |
| THE Eatapia Club Limited | Information & communication | 2020 |
| THE Fundraising Foundry Limited | Administrative & support | 2020 |
| THE Garden City Bread Company Limited | Wholesale & retail | 2013 |
| THE Grange Salon Ltd | Other services | 2025 |
| THE Heritage Network Limited | Professional & scientific | 1998 |
| THE Hub 369 Ltd | Arts & recreation | 2026 |
| THE Last Dog Productions Ltd | Information & communication | 2019 |
| THE Leading Lady Bookshop Ltd | Wholesale & retail | 2026 |
| THE Lounge Male Grooming Ltd | Other services | 2012 |
| THE MUU Limited | Professional & scientific | 2020 |
| THE Notary Public Hertfordshire Limited | Professional & scientific | 2025 |
| THE OFF Licence Group Ltd | Wholesale & retail | 2022 |
| THE Practical Windows Company Ltd | Other services | 2018 |
| THE Quadrant (Newark Close) Management Company Limited | Agriculture & fishing | 1991 |
| THE Recruitment Firm Ltd | Administrative & support | 2024 |
| THE Rose Public House Ltd | Hospitality | 2021 |
| THE RT & CM Parker Family Partnership LLP | | 2019 |
| THE Rugby Trainer Academy Ltd | Education | 2023 |
| THE Rugby Trainer Limited | Education | 2021 |
| THE Sakal Mission Ltd | Education | 2023 |
| THE Salon (Letchworth) Ltd | Other services | 2014 |
| THE Softernet Limited | Real estate | 2022 |
| THE Spencer Group Holdings Limited | Professional & scientific | 2007 |
| THE Spencer Group Limited | Administrative & support | 2001 |
| THE Techie Whisperer Limited | Information & communication | 2014 |
| THE Telephone Guestbook Ltd | Administrative & support | 2022 |
| THE Third Place (Letchworth) Ltd | Wholesale & retail | 2011 |
| THE Tilers Counter Ltd | Wholesale & retail | 2026 |
| THE Whisky Cafe Limited | Hospitality | 2019 |
| THE Wyck Estate Ltd | Administrative & support | 2022 |
| THE XV Club Ltd | Professional & scientific | 2026 |
| THE308FOUNDATION Ltd | Professional & scientific | 2026 |
| Thecareinn Limited | Other services | 2025 |
| Thee Grapevine Ltd | Hospitality | 2016 |
| Then WE Walked Ltd | Information & communication | 2022 |
| Therecycled.App Limited | Wholesale & retail | 2026 |
| Thinkshield Limited | Information & communication | 2006 |
| Thinkvitals Ltd | Information & communication | 2016 |
| Thirty 30 Limited | Professional & scientific | 2015 |
| This IS BE Creative Limited | Professional & scientific | 2021 |
| Thomaspol Ltd | Transport & logistics | 2013 |
| Thongtavee Limited | Health & social care | 2022 |
| Thorne Creative Services Limited | Professional & scientific | 2008 |
| THP Services Ltd | Professional & scientific | 2018 |
| THP Systems Ltd | Administrative & support | 2010 |
| Three SIX Properties Ltd | Construction | 2021 |
| Threedy Ltd | Wholesale & retail | 2020 |
| Threedy Printers Limited | Manufacturing | 2017 |
| Thrive Business Services Limited | Professional & scientific | 2009 |
| Thrive&Pour Ltd | Hospitality | 2025 |
| Thriving Stars Academy Ltd | Arts & recreation | 2023 |
| Thriving Stars Active Ltd | Education | 2025 |
| Thumos Limited | Information & communication | 2025 |
| Thurnall Close Management Company Limited | Households | 1972 |
| Tide & Vine Limited | Administrative & support | 2017 |
| Tilanoma Holdings Limited | Financial services | 2024 |
| Tile Hill G&Cs Limited | Administrative & support | 2024 |
| Tile Hill Group Limited | Financial services | 2024 |