| THE Puzzle Seed Company Limited | Wholesale & retail | 2025 |
| THE Pytchley Autocar Co. Ltd | Wholesale & retail | 2018 |
| THE Pytchley Golf Lodge Limited | Arts & recreation | 2004 |
| THE Pytchley Group Limited | Information & communication | 2025 |
| THE Quality Assurance Network Ltd | Administrative & support | 2021 |
| THE Queen's Arms Limited | Hospitality | 2020 |
| THE RAJ Restaurant 1991 Ltd | Hospitality | 2023 |
| THE Real Sole Family Ltd | Wholesale & retail | 2018 |
| THE Regent ST Cattery Ltd | Other services | 2024 |
| THE Results Centre Limited | Education | 2005 |
| THE Roots Merchant Ltd | Wholesale & retail | 2018 |
| THE Rotolin Bearing Company Ltd | Manufacturing | 2005 |
| THE Rust Bucket Rally Limited | Arts & recreation | 2017 |
| THE Ryhill Partnership Ltd | Education | 2015 |
| THE Scribble Shed Ltd | Other services | 2020 |
| THE Self Build Builder Ltd | Construction | 2024 |
| THE Shire (Kettering) Ltd | Hospitality | 2024 |
| THE Shires Junior Golf Tour Ltd | Arts & recreation | 2021 |
| THE SJ Group Northants Limited | Other services | 2025 |
| THE Social Travel Club Limited | Real estate | 2009 |
| THE Society for Companion Animal Studies Ltd. | Education | 1998 |
| THE Spires RTM Company Ltd | Households | 2012 |
| THE Starlight Dance Group Ltd | Arts & recreation | 2022 |
| THE Sugar Barn Limited | Wholesale & retail | 2015 |
| THE Sweet Barn Limited | Hospitality | 2022 |
| THE T Room Ltd | Hospitality | 2023 |
| THE Talented Fitter Company Ltd | Other services | 2018 |
| THE Terms Office Ltd | Professional & scientific | 2025 |
| THE Tileportfolio Limited | Wholesale & retail | 2020 |
| THE Trading Edge Co. Limited | Professional & scientific | 2011 |
| THE Training Space Limited | Education | 2005 |
| THE Twin Plug Investment Company Limited | Real estate | 2021 |
| THE Van With NO Name Ltd | Arts & recreation | 2025 |
| THE Vincent H.R.D. Owners Club Limited | Extraterritorial | 2010 |
| THE Wama's Restaurants Ltd | Hospitality | 2020 |
| THE Watermill @ Ringstead Limited | Hospitality | 2023 |
| THE Watermill Holiday Homes Limited | Hospitality | 2023 |
| THE Wellbeing LAB Ltd | Health & social care | 2025 |
| THE Wesley Group Limited | Information & communication | 2016 |
| THE Wharf (Bridge Street) Management Company Limited | Households | 2007 |
| THE White Lion Geddington Ltd | Hospitality | 2016 |
| THE Whole Shebang Auctions Limited | Wholesale & retail | 2016 |
| THE Yaboo Company Limited | Information & communication | 1998 |
| Theapay Technologies Limited | Wholesale & retail | 2018 |
| Theia Digital Ltd | Information & communication | 2023 |
| Themevalley Developments Limited | Real estate | 1989 |
| Theneurowellnessproject Ltd | Education | 2026 |
| Theoudandbloomco Ltd | Wholesale & retail | 2025 |
| Thermex AFC Limited | Extraterritorial | 1994 |
| Thermex Industries Limited | Extraterritorial | 1974 |
| Thermo Express Delivery Ltd | Transport & logistics | 2026 |
| Thethamesuk Ltd | Manufacturing | 2023 |
| Thetraining.Shop Ltd | Education | 2017 |
| Thing of Beauty Limited | Information & communication | 2015 |
| Third EYE Drive Thru Ltd | Wholesale & retail | 2024 |
| Third Way Experiences Ltd | Hospitality | 2025 |
| Thirdpull Limited | Real estate | 2025 |
| This IS US PR Limited | Professional & scientific | 2020 |
| Thistleboon Estates Limited | Real estate | 2015 |
| Thomas & Briggs (Twywell) Limited | Construction | 1978 |
| Thomas Binder Limited | Information & communication | 2026 |
| Thomas Patrick Estate Agents Limited | Real estate | 2013 |
| Thomman&Sons Limited | Real estate | 2026 |
| Thompson & Davies Ltd | Real estate | 2018 |
| Thompson & Hall Limited | Transport & logistics | 2008 |
| Thomson Brickwork Ltd | Construction | 2019 |
| Thorney Clothing Limited | Wholesale & retail | 2023 |
| Thorough Plumber Limited | Construction | 2015 |
| Thorpe Langton Management (Property) Ltd | Real estate | 2025 |
| Thrapston Barber Ltd | Other services | 2024 |
| Thrapston Festival of Voice Ltd | Arts & recreation | 2024 |
| Three Cranes Inn Limited | Hospitality | 2023 |
| Three Doors Down Ltd | Other services | 2024 |
| Three Gentlemen Limited | Manufacturing | 2025 |
| Three Pipers Property (HL) Ltd | Real estate | 2023 |
| Three Pipers Property Ltd | Real estate | 2020 |
| Thrillology Limited | Wholesale & retail | 2019 |
| Thursfield & Co,Limited | Wholesale & retail | 1955 |
| TIA Gardner Limited | Financial services | 2015 |
| Ticcea Refrigeration Limited | Administrative & support | 2013 |
| Tida 4U Ltd | Transport & logistics | 2025 |
| Tidybloom Ltd | Administrative & support | 2025 |
| Tiffany's Ltd | Hospitality | 2023 |
| Tiger Claims Limited | Extraterritorial | 2000 |
| Tiggs Collective Limited | Wholesale & retail | 2025 |
| Tijon Consulting Ltd | Information & communication | 2018 |
| Tijon Properties Ltd | Real estate | 2020 |
| TIM Jones Holdings Ltd | Financial services | 2020 |
| TIM Shoveller Board Advisory Limited | Professional & scientific | 2026 |
| Timber Yeti Ltd | Agriculture & fishing | 2024 |
| Time Manufacturing Acquisition (UK) Limited | Administrative & support | 2017 |
| Timely Advice Limited | Education | 2012 |
| Timloc Building Products Limited | Extraterritorial | 1968 |
| Timsons Engineering Limited | Manufacturing | 2014 |
| Tina Cleaning Services Ltd | Administrative & support | 2019 |
| Tios Drinks Limited | Other services | 2020 |
| Tiraz Group of Companies Ltd | Wholesale & retail | 2024 |
| Titan Pensions & Investments Limited | Financial services | 1988 |
| TJ Workz Ltd | Extraterritorial | 2024 |
| TK Humba Limited | Health & social care | 2019 |