| International Therapeutic Proteins Limited | Professional & scientific | 2006 |
| Interrecruit Limited | Extraterritorial | 1988 |
| Interregs Limited | Information & communication | 1963 |
| Intersite Limited | Construction | 1998 |
| Intonation Limited | Professional & scientific | 1985 |
| Iops Limited | Professional & scientific | 2005 |
| Iquantum Ltd | Information & communication | 2025 |
| Irongate Homes Ltd | Real estate | 2010 |
| IS Research Ltd | Information & communication | 2007 |
| Isle of Wight Holidays Limited | Extraterritorial | 2005 |
| Isopod Consortium Limited Partnership | | 2025 |
| IT Computers Limited | Extraterritorial | 2003 |
| IT Consult Limited | Information & communication | 1998 |
| It-Reprise Limited | Information & communication | 1995 |
| ITS NOT Rubbish Limited | Information & communication | 2007 |
| J & H Bailey Associates Limited | Professional & scientific | 2007 |
| J & M Anderson Limited | Extraterritorial | 2006 |
| J and T Ales Limited | Wholesale & retail | 2005 |
| J Clark Joinery Limited | Manufacturing | 2002 |
| J Griffin Contracts Limited | Construction | 2007 |
| J L a Associates Limited | Professional & scientific | 1991 |
| J S Housing Limited | Real estate | 2002 |
| J Shaw Contracts Ltd | Construction | 2007 |
| J W & H Design Limited | Manufacturing | 2002 |
| J&Co Caring Solutions Ltd | Health & social care | 2025 |
| J-Hire Limited | Transport & logistics | 2002 |
| J.E.D. Interactive Training Limited | Information & communication | 1999 |
| J.E.L. Plumbing & Heating Limited | Construction | 2007 |
| J.G. Design Solutions Limited | Information & communication | 2007 |
| J.K. Build Limited | Construction | 2002 |
| J.M.S. Services Limited | Professional & scientific | 1985 |
| J.P.S. Farming Limited | Agriculture & fishing | 1995 |
| J.Q. Carpets Limited | Wholesale & retail | 2003 |
| Jacobs Construction (Holdings) Limited | Construction | 1995 |
| Jacobs Construction Limited | Construction | 1990 |
| Jacobs Joinery & Shop Fitting Ltd. | Manufacturing | 1997 |
| James Hofeld Limited | Professional & scientific | 2007 |
| James Site Services Limited | Administrative & support | 2006 |
| Jane Webber Training Ltd | Professional & scientific | 2024 |
| Jarna & Co Ltd | Hospitality | 2019 |
| Jaylec Limited | Construction | 2002 |
| Jedbridge Properties Limited | Financial services | 2000 |
| Jesterbear Limited | Professional & scientific | 1997 |
| JHD Engineering Ltd | Manufacturing | 2004 |
| Jimz GRP Limited | Wholesale & retail | 2005 |
| JJ Dunne Ltd | Construction | 2014 |
| JJR Accounting Limited | Professional & scientific | 2006 |
| JJT Associates Limited | Professional & scientific | 2006 |
| JL Investments U.K. Limited | Other services | 2023 |
| Jodal Flatlets (Southsea) Limited | Real estate | 1978 |
| Jogging on Limited | Arts & recreation | 2007 |
| John Blackman Arboriculture Fencing & Estate Maintenance Services Limited | Administrative & support | 2003 |
| John Huntley Holdings Limited | Administrative & support | 2007 |
| John Rook (Manor Farm) Limited | Agriculture & fishing | 1980 |
| John Rook Limited | Professional & scientific | 1958 |
| John Smart Limited | Real estate | 1995 |
| Johnsons Carriage Masters Limited | Professional & scientific | 2007 |
| Joint Finance Solutions Limited | Financial services | 2004 |
| Jonathan COX Associates Limited | Professional & scientific | 2003 |
| Jones Marine Technologies Limited | Professional & scientific | 2006 |
| JPF Networks Limited | Information & communication | 2002 |
| JPL4 Limited | Wholesale & retail | 2003 |
| JPS Construction Services Ltd | Construction | 2004 |
| Jtfc Consulting Ltd | Information & communication | 2022 |
| Juara Limited | Professional & scientific | 2003 |
| Jube Optical Ltd | Health & social care | 2024 |
| Just Jointing Limited | Construction | 1998 |
| Just Salt Limited | Wholesale & retail | 2006 |
| Justdisk Limited | Information & communication | 1993 |
| Justus Corporation Limited | Real estate | 2002 |
| Justus JV Limited | Administrative & support | 2004 |
| K G Sprayers (Aldershot) Limited | Manufacturing | 2004 |
| K J Trading UK Limited | Construction | 2005 |
| K S P Associates Limited | Information & communication | 1998 |
| K. T. Design Ltd. | Professional & scientific | 1998 |
| K.E.S. Power and Light Limited | Manufacturing | 1991 |
| K.W. Barron Limited | Professional & scientific | 2003 |
| K2 Programming Services Limited | Professional & scientific | 1996 |
| Kalibre Kitchens Limited | Construction | 2004 |
| Kalika Connect Ltd | Transport & logistics | 2022 |
| Kalotec Building Design Specialists Limited | Construction | 2003 |
| KAM Productions Limited | Arts & recreation | 2007 |
| Kandice Ltd | Health & social care | 2014 |
| Karen Woods Journalism and Communications Limited | Administrative & support | 2004 |
| Kashiba Properties Limited | Construction | 1994 |
| Kate Bird Limited | Wholesale & retail | 2003 |
| Kazim-Tylor Consulting Limited | Information & communication | 2016 |
| KB Barbers Ltd | Other services | 2018 |
| Keith Sanger Associates Limited | Professional & scientific | 1988 |
| Kelcey (1996) Limited | Professional & scientific | 1996 |
| KEN Geering Associates Limited | Wholesale & retail | 2017 |
| Kenan CS Ltd | Hospitality | 2021 |
| Kenneth West Limited | Wholesale & retail | 1982 |
| Kenwood Limited | Manufacturing | 1966 |
| Kestrel Associates Limited | Education | 1994 |
| Kestrel Security Systems Limited | Administrative & support | 2005 |
| Keyword Advertising Limited | Information & communication | 1999 |
| Kfws Limited | Hospitality | 2001 |
| Khristians Limited | Construction | 2006 |
| Kickback Media Limited | Information & communication | 1994 |