| Skyorcus Ltd | Information & communication | 2024 |
| Smart & Son(Livestock)Limited | Agriculture & fishing | 1967 |
| Smith Taylor & Associates Limited | Professional & scientific | 1998 |
| SMJ Commercial Ltd | Hospitality | 2022 |
| SMS Trading Limited | Real estate | 2002 |
| Snooze Hotel Corby Ltd | Hospitality | 2022 |
| Solar Computer Systems Limited | Wholesale & retail | 2000 |
| Sona Construction Limited | Construction | 2001 |
| South Court Environmental Limited | Other services | 1993 |
| Spectrum T.P. Limited | Health & social care | 2002 |
| Spenpost Limited | Real estate | 1997 |
| Spun OUT Partners Limited | Real estate | 2003 |
| Spurgeons | Health & social care | 2000 |
| ST Stephens Hongkong Limited | Hospitality | 2019 |
| ST. Clements Services Limited | Information & communication | 1989 |
| ST. Peters Mews Residents Management Limited | Households | 1989 |
| Stanhope Capital Partners Limited | Extraterritorial | 2006 |
| Stanhope Holdco Limited | Professional & scientific | 2025 |
| Steele & Bray Limited | Construction | 1995 |
| Sterling Design Limited | Professional & scientific | 1995 |
| Sterling Press Limited | Manufacturing | 1989 |
| Stevan Hawkins Limited | Agriculture & fishing | 1998 |
| Steve Grant Plumbing & Heating Limited | Construction | 2006 |
| STUDIO65 Limited | Arts & recreation | 2000 |
| SUE Davis Limited | Other services | 2003 |
| Summerisle Finance Ltd | Professional & scientific | 2012 |
| Sundora Foods Limited | Extraterritorial | 2005 |
| Sunnyforward Property Management Limited | Households | 2004 |
| Sunshine Farm (Brixworth) Limited | Other services | 2006 |
| Supercool Central Limited | Construction | 2008 |
| Superhighway Systems Limited | Information & communication | 2004 |
| System Designs Limited | Professional & scientific | 1990 |
| Sywell Aviation Limited | Transport & logistics | 1996 |
| T F Bone (Plumbing) Limited | Construction | 2003 |
| T M Halloran Limited | Construction | 2006 |
| T. R. Bullworthy Limited | Wholesale & retail | 2002 |
| T. Reynolds Limited | Administrative & support | 2007 |
| T.A.P. Installations Limited | Administrative & support | 2007 |
| T.T.P. Contract Drivers Limited | | 1998 |
| Tabs @ 42 Limited | Health & social care | 2006 |
| Tachyon Associates Limited | Information & communication | 2002 |
| Tagquest Limited | | 1986 |
| Tangential Limited | Information & communication | 1999 |
| Tapiochre Limited | Information & communication | 2003 |
| Taurus Graphics Limited | Professional & scientific | 2002 |
| TCI Seating Limited | Manufacturing | 2000 |
| Tebu-Bio Limited | Administrative & support | 1998 |
| Techno-Vision Systems Limited | Other services | 1987 |
| Tema - Isenmann Limited | Administrative & support | 1985 |
| Tempera Digital Limited | Other services | 2006 |
| Tetheringstones Limited | Professional & scientific | 1996 |
| THE 78 Derngate Northampton Trust | Arts & recreation | 1998 |
| THE Alumasc Group PLC | Professional & scientific | 1983 |
| THE Atlantic Instrument Equipment Co., Ltd | Professional & scientific | 2025 |
| THE Bake House Catering Company Limited | Hospitality | 2002 |
| THE British Association of Rally Schools Limited | Other services | 1995 |
| THE Chris Solbe Partnership Limited | Other services | 2006 |
| THE Garage at Blakesley Limited | Wholesale & retail | 1996 |
| THE Garage Equipment Association Limited | Other services | 1994 |
| THE Grange Apartments (Thistle Drive, Desborough) Management Company Limited | Extraterritorial | 2005 |
| THE Holywell Partnership Limited | Professional & scientific | 2004 |
| THE Insulin Dependent Diabetes Trust | Health & social care | 1996 |
| THE Mortgage Doctors Limited | Financial services | 2003 |
| THE Northampton Grocer Limited | Wholesale & retail | 2020 |
| THE Pytchley Hunt Masters 2009 Limited | Agriculture & fishing | 2009 |
| THE RAJ (GB) Ltd | Real estate | 1999 |
| THE Richardsons Group Limited | Hospitality | 1988 |
| THE Richardsons Holding Group Limited | Administrative & support | 1978 |
| THE Rocking Horse Day Nursery Limited | Education | 2003 |
| THE Simcup Company Ltd | Manufacturing | 2005 |
| THE Teeton Lane Development Company Ltd | Real estate | 2023 |
| Thorn Electrical (Northampton) Limited | Administrative & support | 2007 |
| Three Chimneys Farm UK Ltd | Agriculture & fishing | 2026 |
| Timefiber Limited | Wholesale & retail | 2024 |
| Tingdene Marinas International Ltd | Real estate | 2025 |
| Topham Investments Limited | Real estate | 2004 |
| Total Solution Services (UK) Ltd | Administrative & support | 2005 |
| Total-Fishing (UK) Limited | Information & communication | 2003 |
| Totan Jewellers Ltd | Wholesale & retail | 1999 |
| Tranex Holdings Limited | Professional & scientific | 2006 |
| Treeworx Limited | Agriculture & fishing | 2007 |
| Trevor Denny Engineering Limited | Manufacturing | 2002 |
| Trinity Services (Northampton) Limited | Wholesale & retail | 2003 |
| True Buddha School (Tsen RU Tang) Limited | Other services | 1995 |
| Trueself Limited | Education | 1999 |
| TST 2017 Limited | Other services | 2017 |
| TT & C Developments Limited | Real estate | 2021 |
| Turner Designs Limited | Professional & scientific | 2006 |
| Turweston Flight Centre Limited | Transport & logistics | 1989 |
| Tusting & Burnett (1938) Limited | Manufacturing | 1938 |
| Tyre-Line Original Equipment Limited | Manufacturing | 1983 |
| Unique Build Property Company Limited | Construction | 1999 |
| Uniquesolve Enterprises (Braunston) Ltd | Real estate | 2015 |
| Uniquesolve Enterprises (Olney) Limited | Real estate | 2014 |
| Uniquesolve Enterprises Limited | Construction | 1992 |
| Utile Engineering Co. Limited(The) | Manufacturing | 1982 |
| Van Allen Foods Limited | Wholesale & retail | 1990 |
| Vektor Maintenance Limited | Administrative & support | 2017 |
| Veldt Properties Ltd | Real estate | 2019 |
| Vembanad Distributors Ltd | Wholesale & retail | 2021 |