| Thewomen'Sempowermentgroup C.I.C. | Health & social care | 2025 |
| Thewonkyhandleco Ltd | Wholesale & retail | 2026 |
| Thextensionlounge Ltd | Other services | 2025 |
| Thingamagy Limited | Wholesale & retail | 2020 |
| Think Prop Limited | Real estate | 2023 |
| THINK3SIXTY Communications Limited | Administrative & support | 2013 |
| Thinkbox Design Ltd | Professional & scientific | 2025 |
| Thinkingdoing Ltd | Professional & scientific | 2021 |
| Thinktrail Limited | Information & communication | 2024 |
| Thinox Construction Management Ltd. | Professional & scientific | 2014 |
| Third Drawer Down Ltd | Wholesale & retail | 2021 |
| Third World Traid Ltd | Wholesale & retail | 2005 |
| Thirteen AI Ltd | Professional & scientific | 2025 |
| Thirteen Moments Ltd | Financial services | 2025 |
| Thirty Seven Spaces Ltd | Real estate | 2025 |
| Thisay Properties Ltd | Real estate | 2025 |
| Thistimenextyear Limited | Information & communication | 2008 |
| Thistle Pressure Washer Services Limited | Manufacturing | 2008 |
| Thmac Ltd | Real estate | 2017 |
| Thoe Properties Limited | Real estate | 2024 |
| Thomas (Haulage) Limited | Construction | 1992 |
| Thomas Bird Shoes Limited | Wholesale & retail | 2015 |
| Thomas Cole Ltd | Administrative & support | 2026 |
| Thomas Dickens Developments Ltd | Construction | 2015 |
| Thomas Fire Consultancy Ltd | Public administration | 2018 |
| Thomas Grey Creative Solutions Ltd | Professional & scientific | 2014 |
| Thomas Holland Racing Ltd | Arts & recreation | 2023 |
| Thomas Kraits Investments Limited | Financial services | 2019 |
| Thomas Kraits Ltd | Information & communication | 2019 |
| Thomas Kraits United Kingdom Limited | Information & communication | 2015 |
| Thomas Red Ltd | Wholesale & retail | 2020 |
| Thomas Robert Consulting Limited | Construction | 2022 |
| Thomas Walden Transport Ltd | Transport & logistics | 2025 |
| Thomason Investments Limited | Real estate | 2004 |
| Thompson Flooring Limited | Construction | 2005 |
| Thompson Ground Care Ltd | Administrative & support | 2018 |
| Thompson Hedge and Garden Services Ltd | Administrative & support | 2017 |
| Thompson Tree (Northants) Ltd | Agriculture & fishing | 2010 |
| Thomson Family Property Holdings Limited | Financial services | 2025 |
| Thomson Gray Wealth Management Limited | Financial services | 2011 |
| Thomson Group Holdings Limited | Financial services | 2025 |
| Thomson Group Limited | Financial services | 2018 |
| Thomsons Care Services Ltd | Health & social care | 2026 |
| Thor Civils Limited | Construction | 2010 |
| Thor Security and Fencing Ltd | Administrative & support | 2022 |
| Thorlo Ltd | Administrative & support | 2019 |
| Thorneycroft Cladding Solutions Ltd | Construction | 2026 |
| Thornton Hall Management Company (Northampton) Limited | Real estate | 2010 |
| Thornton House Management Company Limited | Households | 1982 |
| Thornton Mews Management Company Limited | Households | 1989 |
| Thoroughflush Ltd | Manufacturing | 2019 |
| Thorpe Dock Consulting Limited | Professional & scientific | 2022 |
| Thorpe Enterprises Limited | Financial services | 2019 |
| Thorpe Holdings Ltd | Extraterritorial | 2009 |
| Thorpeville Mews Management Company Limited | Households | 2024 |
| Thorplands Ltd | Wholesale & retail | 2015 |
| Thorplands NN3 Limited | Hospitality | 2023 |
| Thorplands Supermarket Limited | Wholesale & retail | 2003 |
| Thoughtlogik Technology Solutions Ltd | Information & communication | 2021 |
| Thp.Property Limited | Real estate | 2024 |
| Thrapston Garage and Titty HO Motor Company Limited | Wholesale & retail | 2010 |
| Thread & Print Studio Ltd | Manufacturing | 2024 |
| Thread Alchemy Ltd | Wholesale & retail | 2025 |
| Threadsvelora Ltd | Wholesale & retail | 2026 |
| Three Arches Farm LLP | | 2020 |
| Three Bears Literacy Consultancy Ltd | Education | 2011 |
| Three Counties Electrical (Northampton) Ltd | Construction | 2016 |
| Three Counties Housing Care and Support Ltd | Hospitality | 2009 |
| Three Dots Ltd | Professional & scientific | 2016 |
| Three Gables Ltd. | Real estate | 1999 |
| Three Oaks Joinery Limited | Manufacturing | 2019 |
| Three Shires Agronomy Limited | Agriculture & fishing | 2004 |
| Three Shires Driving Centre Limited | Education | 2014 |
| Threesixty HR Ltd | Professional & scientific | 2014 |
| Threeways Garage (Northampton) Limited | Wholesale & retail | 2009 |
| Thrift Oak Management Company Ltd | Extraterritorial | 2015 |
| Thrive Accelerator Consulting Limited | Professional & scientific | 2024 |
| Thrive at Hideaway Wood Farm CIC | Agriculture & fishing | 2024 |
| Thrive Gcse Ltd | Education | 2026 |
| Thrive Health Group Ltd | Health & social care | 2025 |
| Thrive Occupational Therapy Services Ltd | Health & social care | 2010 |
| Thrive Online Coaching Ltd | Arts & recreation | 2020 |
| Thrive Poke Bar Ltd | Hospitality | 2025 |
| Thriving Hearts Residential Homes Ltd | Health & social care | 2025 |
| Thriving Minds Project CIC | Health & social care | 2022 |
| Throne Art Limited | Professional & scientific | 2019 |
| Throop Milling Limited | Real estate | 2017 |
| Through the Night Limited | Health & social care | 2014 |
| Through the Woods Counselling Ltd | Health & social care | 2024 |
| Throughline Live Limited | Professional & scientific | 2026 |
| Thywill Imports Ltd | Wholesale & retail | 2024 |
| Ti.Mvt Ltd | Financial services | 2024 |
| Tick Tonic Ltd | Professional & scientific | 2025 |
| Tidish Ltd | Professional & scientific | 2025 |
| Tidy Numbers Ltd. | Professional & scientific | 2011 |
| Tidycubs Ltd | Manufacturing | 2026 |
| TIE the Knot Northampton LLP | | 2023 |
| Tiered Seating Ltd | Extraterritorial | 2009 |
| Tifetube Atelier Ltd | Manufacturing | 2023 |
| Tiffield Properties Limited | Construction | 2017 |