| Tonmead Flats Management Company Limited | Households | 1983 |
| Tonmead Land Management Company Limited | Households | 1983 |
| Tonre Limited | Health & social care | 2022 |
| Tons Services Limited | Professional & scientific | 2019 |
| Tony Brennan Consultancy Limited | Professional & scientific | 2014 |
| Tony Constr Ltd | Construction | 2017 |
| Tony Jones Florist Limited | Wholesale & retail | 2022 |
| Tony Murphy Developments Limited | Construction | 2022 |
| Tony Perry Limited | Manufacturing | 2010 |
| TOO Bright Baby Lighting Limited | Information & communication | 2023 |
| Took TM Ltd | Construction | 2023 |
| Tool & Fastener Solutions Limited | Wholesale & retail | 2000 |
| Toolbox Rigging Ltd | Information & communication | 2014 |
| Toolbox Titans Limited | Wholesale & retail | 2024 |
| Tools Rent Limited | Administrative & support | 2024 |
| Toolstation Europe Limited | Wholesale & retail | 2012 |
| Toolstation Holdings Limited | Extraterritorial | 1956 |
| Toolstation Limited | Wholesale & retail | 2002 |
| Toosh Ltd | Construction | 2021 |
| Top 4 the Tots Ltd | Wholesale & retail | 2022 |
| Top Auto Imports Ltd | Wholesale & retail | 2025 |
| Top Beauty MAB Limited | Other services | 2023 |
| Top Boot Factory Management Company Limited | Households | 2006 |
| Top Class Designs (Northampton) Limited | Manufacturing | 2008 |
| Top DEL Ltd | Transport & logistics | 2019 |
| Top Dog Housekeeping Limited | Administrative & support | 2018 |
| Top END Ltd | Administrative & support | 2020 |
| Top Flight Cars Ltd | Wholesale & retail | 2017 |
| Top HAT Racing Limited | Arts & recreation | 2025 |
| Top HAT Theatre School Limited | Arts & recreation | 2017 |
| Top House Building Contractors Ltd | Construction | 2017 |
| Top House Building Developments Limited | Construction | 2021 |
| Top House Design and Build Limited | Manufacturing | 2025 |
| Top Kitchens&Bath Installing Ltd | Construction | 2025 |
| Top Level Security Limited | Other services | 2018 |
| Top Move Property Limited | Administrative & support | 2010 |
| Top Rank Transport Ltd | Transport & logistics | 2022 |
| Top Scenery Ltd | Manufacturing | 2018 |
| Top Sourcing Ltd | Administrative & support | 2018 |
| Top Tech Trading Ltd | Wholesale & retail | 2021 |
| Top Window Covering UK Limited | Wholesale & retail | 2019 |
| Topaz Solutions Limited | Professional & scientific | 2009 |
| Topcat Civils Limited | Construction | 2011 |
| Topez Business Solutions Ltd | Professional & scientific | 2015 |
| Topflight Carpentry Ltd | Construction | 2025 |
| Topham Holdings Ltd | Financial services | 2012 |
| Tophaven Sustainable Construction Limited | Professional & scientific | 2002 |
| Topi's Barbers Ltd | Other services | 2021 |
| Topleader Limited | Construction | 1980 |
| Topo Land Surveys Ltd | Professional & scientific | 2021 |
| Tops Express Northampton Limited | Hospitality | 2026 |
| Topslide International UK Limited | Manufacturing | 2013 |
| Topspeed Automotive Limited | Wholesale & retail | 2004 |
| Toptalent Aspire Ltd | Education | 2020 |
| Toptrees Limited | Agriculture & fishing | 2022 |
| Toras Transport Ltd | Transport & logistics | 2021 |
| TORC2 Ltd | Professional & scientific | 2013 |
| Torccrafting Limited | Wholesale & retail | 2021 |
| Torcprotective Ltd | Professional & scientific | 2017 |
| Torimaru Ltd | Manufacturing | 2026 |
| Torkington Indoor Storage Limited | Administrative & support | 2016 |
| Tornberg and Tester Limited | Extraterritorial | 1957 |
| Torquemeters Holdings Limited | Financial services | 2020 |
| Torquemeters Limited | Manufacturing | 1951 |
| Torrent Ltd | Information & communication | 2019 |
| Toru Limited | Professional & scientific | 2008 |
| Torus Electrical Ltd | Construction | 2025 |
| Torvic Associates Limited | Manufacturing | 2002 |
| Toshi Consultants Limited | Professional & scientific | 2015 |
| Toshi Karate Club Ltd | Education | 2019 |
| Toso Ltd | Other services | 2019 |
| Total B Constructions Ltd | Construction | 2018 |
| Total Body Confidence Limited | Health & social care | 2024 |
| Total Broadband Solutions Ltd | Information & communication | 2024 |
| Total Control Pro Limited | Information & communication | 2001 |
| Total Dosing Solutions Limited | Wholesale & retail | 2015 |
| Total Fastener Supplies Ltd | Professional & scientific | 2015 |
| Total Funding Solutions Limited | Financial services | 2020 |
| Total Hire Solutions Ltd | Administrative & support | 2019 |
| Total Motor Vogue Limited | Wholesale & retail | 2016 |
| Total Networking Solutions Ltd | Information & communication | 2024 |
| Totalconstruct & Maintenance Limited | Construction | 2024 |
| Totally Bespoke Building Limited | Construction | 2014 |
| Totally Converged Solutions Ltd | Information & communication | 2009 |
| Totally Tiva Ltd | Professional & scientific | 2019 |
| Totalman Healthcare Limited | Health & social care | 2017 |
| Toto Tranzit Ltd | Transport & logistics | 2016 |
| Totty Teas Limited | Hospitality | 2014 |
| Totum Finance Limited | Extraterritorial | 2015 |
| Totus Holdings Limited | Financial services | 2024 |
| Touch of Magic Cosmetics Ltd | Extraterritorial | 2018 |
| Tour Design Golf Ltd | Manufacturing | 2022 |
| Tove Learning Trust | Education | 2011 |
| Tove Valley Roofing Ltd | Construction | 2022 |
| TOW Buddys Ltd | Manufacturing | 2024 |
| Toward Consultancy 2024 Limited | Professional & scientific | 2024 |
| Towcester Brickwork Limited | Construction | 2021 |
| Towcester Pilates Limited | Arts & recreation | 2014 |
| Towcester Road Management Company Limited | Real estate | 2006 |
| Tower Boots London Limited | Wholesale & retail | 1998 |