| John Logie Motorboats Limited | Administrative & support | 2019 |
| John Nike Leisuresport Limited | Arts & recreation | 1984 |
| John Pascoe Financial Services Ltd | Financial services | 2023 |
| John Paul Construction (UK) Limited | Construction | 2024 |
| John Paul Contracts Limited | Construction | 2011 |
| John Riley Limited | Construction | 2015 |
| Johns Tiling and Bathroom Ltd | Construction | 2025 |
| Johnstone Roofing Ltd | Construction | 2021 |
| Jonathan Barr Associates Limited | Hospitality | 2014 |
| Jordan Construction Limited | Construction | 1997 |
| Josado Limited | Health & social care | 2015 |
| Josef Holmes Media Ltd | Professional & scientific | 2019 |
| Joselyne Healthcare Ltd | Administrative & support | 2016 |
| Joy’S Handyman Ltd | Construction | 2026 |
| JP Holdaway Group Ltd | Construction | 2019 |
| JP Technical Consulting (UK) Limited | Professional & scientific | 2005 |
| JPA Group Limited | Administrative & support | 2000 |
| JPD Solar Solutions Ltd | Energy | 2023 |
| JPH Drainage Ltd | Water & waste | 2025 |
| JPH FM Ltd | Construction | 2025 |
| JPH Projects Ltd | Construction | 2025 |
| JPM Future Limited | Transport & logistics | 2018 |
| JPR Ventures Limited | Wholesale & retail | 2008 |
| Jprice Technology Services Limited | Administrative & support | 2013 |
| JPS Fabrications Ltd | Manufacturing | 2018 |
| JRG Consultant Engineers Limited | Professional & scientific | 2022 |
| JRG Software Ltd | Information & communication | 2002 |
| JRT (South) UK Ltd | Other services | 2023 |
| JS BMS Controls Limited | Construction | 2011 |
| JS Building Solutions PVT Ltd | Construction | 2024 |
| JS Risk Management Limited | Professional & scientific | 2015 |
| JS Tree & Landscaping Ltd | Administrative & support | 2025 |
| Js&Sons Solutions Limited | Professional & scientific | 2016 |
| JSP International Limited | Professional & scientific | 1994 |
| JT HAY & Straw Limited | Agriculture & fishing | 2019 |
| JT Rejuvenate Ltd | Wholesale & retail | 2026 |
| JTF Enterprises Limited | Information & communication | 2018 |
| Jtfone Limited | Administrative & support | 2012 |
| Jubaida Catering Ltd | Hospitality | 2024 |
| Jubea Property Ltd | Construction | 2023 |
| Jubilee Building Supplies Limited | Wholesale & retail | 1988 |
| Jude & Co Manufacturing Ltd | Manufacturing | 2026 |
| Judge Property Holdings Ltd | Real estate | 2025 |
| Julka and Olek Limited | Wholesale & retail | 2019 |
| Jumping Giraffe Events Limited | Administrative & support | 2016 |
| Jungle Berry Brighton Limited | Wholesale & retail | 2025 |
| Jungle Berry Limited | Wholesale & retail | 2022 |
| Jupiter Biometrics Limited | Administrative & support | 2019 |
| JUPITER22 Ltd | Financial services | 2024 |
| Jupiterlights Productions Limited | Information & communication | 2014 |
| Just Fish and Chips Limited | Hospitality | 2015 |
| Just Lighting Limited | Professional & scientific | 2021 |
| Just Revert Ltd | Wholesale & retail | 2025 |
| JW Lifting Management Services Limited | Construction | 2014 |
| K & B Data Solutions Ltd | Construction | 2019 |
| K a Promore Adom Shops Ltd | Other services | 2017 |
| K B Jewellery Limited | Wholesale & retail | 2024 |
| K C Film and TV Limited | Arts & recreation | 2012 |
| K COX Ltd | Administrative & support | 2015 |
| K Newman Limited | Administrative & support | 2022 |
| K&A Engineering Consultancy Limited | Professional & scientific | 2017 |
| K&K Business Services Ltd | Professional & scientific | 2019 |
| K&M Dream Cars Ltd | Construction | 2019 |
| K1NGS of Vape Ltd | Wholesale & retail | 2018 |
| K3G Total Solutions Ltd | Construction | 2016 |
| K3V Dental Ltd | Health & social care | 2024 |
| K6 Support Solutions Limited | Administrative & support | 2022 |
| Kabisa Ltd | Real estate | 2020 |
| KAC Alarm Company Limited | Manufacturing | 1975 |
| Kadu Prime Vehicle Ltd | Wholesale & retail | 2025 |
| Kaisari Ltd | Professional & scientific | 2024 |
| Kaizen Lifesciences Ltd | Professional & scientific | 2017 |
| Kalobe Media Ltd | Information & communication | 2025 |
| Kalypso Media UK Limited | Information & communication | 2007 |
| KAM3D-AUTOMOTIVE Ltd | Wholesale & retail | 2023 |
| Kamagi Ltd | Manufacturing | 2025 |
| Kanes Technical Solutions Ltd | Information & communication | 2016 |
| Kanica Singh Limited | Professional & scientific | 2019 |
| Kare First Ltd | Health & social care | 2013 |
| Karima's Cravings Limited | Extraterritorial | 2024 |
| Karium Ltd | Wholesale & retail | 1990 |
| Karlsen Group Ltd | Professional & scientific | 2025 |
| Karo Property Ltd | Real estate | 2024 |
| Karoga Corner Ltd | Hospitality | 2024 |
| Karpovics Ltd | Construction | 2026 |
| Kash Karma Limited | Information & communication | 2016 |
| Kate Mcdougle Consulting Limited | Professional & scientific | 2017 |
| Kathure Limited | Professional & scientific | 2010 |
| Katie Ecclestone Ltd | Professional & scientific | 2023 |
| KAY Moden Limited | Professional & scientific | 2019 |
| Kaybee Distribution Ltd | Wholesale & retail | 2016 |
| KB Notary Public Limited | Professional & scientific | 2020 |
| KB Solicitors Limited | Professional & scientific | 2007 |
| KBM Consultancy Limited | Professional & scientific | 2012 |
| KCB Investments Group Limited | Real estate | 2026 |
| KCP Equestrian Ltd | Agriculture & fishing | 2024 |
| KCP Ltd | Information & communication | 2008 |
| KDL Central Limited | Real estate | 2014 |
| Keenfinity Limited | Wholesale & retail | 2024 |
| Keep Compliant Ltd | Information & communication | 2026 |