| Instrumentation & Monitoring Solutions Ltd | Professional & scientific | 2023 |
| Insulated Tools Holdings Limited | Manufacturing | 2010 |
| Insulated Tools MW Limited | Manufacturing | 2016 |
| Insulation Online Limited | Wholesale & retail | 2002 |
| Intelligent Heat & Power Limited | Construction | 2005 |
| Interior Build Solutions Limited | Real estate | 2011 |
| Interline Freight Solutions Ltd. | Transport & logistics | 2014 |
| Intermod Ltd | Wholesale & retail | 2023 |
| International College of Oriental Medicine (U.K.) Limited(The) | Education | 1977 |
| International Logistics Group Limited | Transport & logistics | 1995 |
| International Safety Services Limited | Professional & scientific | 2000 |
| Interspirit Ltd | Extraterritorial | 1999 |
| Intever Ltd | Financial services | 2025 |
| Into Properties Limited | Real estate | 2001 |
| Intuition Finance Ltd | | 2009 |
| Invest and Rental Ltd | Financial services | 2022 |
| Invisible Sword Ltd | Information & communication | 2023 |
| Invisible Sword Productions Ltd | Information & communication | 2016 |
| Iris Systems Limited | Information & communication | 2021 |
| Irsap UK Limited | Wholesale & retail | 1998 |
| Isabel MAY Nails Training Ltd | Extraterritorial | 2021 |
| Isanar Ltd | Professional & scientific | 2023 |
| Ishervon Foundation | Administrative & support | 2019 |
| Island of Tuba Ltd | Wholesale & retail | 2025 |
| Isomanagementsolutions Limited | Professional & scientific | 2014 |
| IT Harmony Ltd | Information & communication | 2019 |
| Italian Food Takeaway Ltd | Hospitality | 2017 |
| Italian Geographic Ltd | Hospitality | 2005 |
| Itex Britan Ltd | Information & communication | 2022 |
| Itexgb Ltd | Information & communication | 2021 |
| IVY Florence Ltd | Other services | 2015 |
| J & E Homes Limited | Real estate | 2018 |
| J & S Agencies Ltd | Manufacturing | 2017 |
| J H Bush Ltd | Financial services | 2026 |
| J R Editorial Services Limited | Information & communication | 2008 |
| J White Construction Ltd | Construction | 2024 |
| J&S Properties(South) Limited | Real estate | 2019 |
| J.Cherie Studios Ltd | Professional & scientific | 2025 |
| J.S.H. Home Improvements Ltd | Construction | 2022 |
| J30 Limited | Wholesale & retail | 2019 |
| J4D Group Ltd | Administrative & support | 2017 |
| JA Media Limited | Information & communication | 2012 |
| Jack Burton Ltd | Information & communication | 2024 |
| Jackson's(Reigate)Limited | Real estate | 1964 |
| Jacob's Ladder Farms Limited | Agriculture & fishing | 2014 |
| Jacobs Electrical Supplies Ltd | Construction | 2024 |
| Jadro Medical Ltd | Health & social care | 2023 |
| Jadro Property Group Ltd | Construction | 2025 |
| Jagel Enterprises Limited | Hospitality | 2008 |
| Jalakar Property Limited | Real estate | 2020 |
| James Knott & SON Ltd | Construction | 2015 |
| James Mckenzie (Wills) Ltd | Professional & scientific | 2009 |
| James Mckenzie Group Limited | Financial services | 2026 |
| James Mckenzie Legal Services Ltd | Professional & scientific | 2018 |
| James Mckenzie Mortgages Limited | Financial services | 2026 |
| James Owen Consultancy Ltd | Information & communication | 2015 |
| Janet Ryan Project Services Ltd | Professional & scientific | 2015 |
| JAS Property Group Ltd | Financial services | 2023 |
| Jayan Food & Wine Ltd | Wholesale & retail | 2026 |
| Jaybee Catering Ltd | Wholesale & retail | 2024 |
| Jaybeeseg Ltd Ltd | Wholesale & retail | 2026 |
| JC30 Group Ltd | Financial services | 2024 |
| JCL Healthcare Services Ltd | Professional & scientific | 2023 |
| JD Holmes Construction Limited | Construction | 2024 |
| JD Wholesalers Limited | Wholesale & retail | 2022 |
| Jeco Pest Control Ltd | Administrative & support | 2022 |
| Jeco Recycling Ltd | Water & waste | 2022 |
| JEL Impact Media Limited | Information & communication | 2024 |
| Jenosteo Therapies Ltd | Health & social care | 2025 |
| Jetting Services Direct Limited | Water & waste | 2014 |
| Jewellery HUT Ltd | Manufacturing | 2021 |
| JEX Pettet & Co Ltd | Professional & scientific | 2024 |
| Jigsaw (Southeast) | Health & social care | 2012 |
| JIM Pirrie Limited | Professional & scientific | 2001 |
| JJB Aviation Consultancy Ltd | Transport & logistics | 2023 |
| JJL Computers Ltd | Wholesale & retail | 2019 |
| Jlbordessoule Technology Ltd | Information & communication | 2017 |
| JNS Couriers Ltd | Transport & logistics | 2018 |
| JNS Engineering Ltd | Construction | 2013 |
| JO Morcom HR and Coaching Ltd | Administrative & support | 2023 |
| Jobctrl Ltd | Information & communication | 2014 |
| JOE B Sports Therapy Limited | Other services | 2025 |
| John Roberts (Bexley) Limited | Real estate | 1992 |
| Jolliff Development Limited | Construction | 2013 |
| Jolliff Homes Limited | Real estate | 2021 |
| JON Budd Design Limited | Professional & scientific | 2009 |
| Jonathan Aubrey Limited | Professional & scientific | 2016 |
| Jonathan Lawrence Ltd | Professional & scientific | 2013 |
| Jones International Trading Limited | Wholesale & retail | 2016 |
| Jordan Perry Ltd | Other services | 2020 |
| Joy's Spice Ltd | Hospitality | 2018 |
| JPC Investing Limited | Real estate | 2019 |
| JPC Rentals Limited | Real estate | 2020 |
| Jpec Building Services Limited | Construction | 2020 |
| Jpec Fire and Security Limited | Public administration | 2023 |
| Jpec Green Energy Limited | Construction | 2023 |
| Jpec Group Holdings Limited | Construction | 2023 |
| JPM Building Ltd | Construction | 2017 |
| JPW Procurement Ltd. | Information & communication | 2015 |
| Jubilee Community Cafe C.I.C. | Hospitality | 2021 |