| JAM Construction Ltd | Manufacturing | 2019 |
| James Fraser Consulting Limited | Professional & scientific | 2010 |
| James Robert Smith | Financial services | 2009 |
| James Upshall Pipe Company (UK) Limited | Manufacturing | 1995 |
| James Whiteside Limited | Manufacturing | 2008 |
| Jamson Innovations Ltd | Other services | 2024 |
| Jamsvg Ltd | Professional & scientific | 2021 |
| JAN Skarbek Advisory Ltd | Professional & scientific | 2026 |
| Jansen Construction Ltd | Construction | 2015 |
| Japanese Market Perspectives Limited | Information & communication | 2011 |
| Jarrett Medical Limited | Health & social care | 2020 |
| Jarvis and White Decorators Ltd | Construction | 2024 |
| Jarvis and White Properties Ltd | Real estate | 2026 |
| Jas.Truscott & SON Limited | Construction | 1937 |
| JAW Storage Limited | Administrative & support | 2020 |
| Jays Barbers (Paddock Wood) Limited | Other services | 2017 |
| JC Hayes Associates Limited | Information & communication | 2015 |
| JC Inc Ltd | Professional & scientific | 2013 |
| JC Lawyers Limited | Professional & scientific | 2014 |
| JC Plant & Civils Ltd | Construction | 2021 |
| Jcmh Accountants Ltd | Professional & scientific | 2013 |
| JCW Consultancy Services Limited | Professional & scientific | 2024 |
| JDI Carpentry Limited | Construction | 2008 |
| Jdjamieson Engineering Ltd | Professional & scientific | 2024 |
| JE Capital Limited | Professional & scientific | 2017 |
| Jeanic Ltd | Health & social care | 2014 |
| Jedwing Limited | Real estate | 2001 |
| JEE Battersea Limited | Real estate | 2015 |
| JEE Group EOT Limited | Administrative & support | 2021 |
| JEE Group Limited | Professional & scientific | 2012 |
| JEE Limited | Mining & quarrying | 1998 |
| Jeenius Limited | Mining & quarrying | 2012 |
| Jegem Limited | Administrative & support | 2012 |
| JEM Publishing Ltd | Information & communication | 2024 |
| Jemma Wilkinson Therapy Limited | Health & social care | 2021 |
| Jemma With a J Limited | Administrative & support | 2015 |
| Jemst Limited | Professional & scientific | 2007 |
| Jendi Limited | Hospitality | 2015 |
| Jennings Orthopaedics Ltd | Health & social care | 2011 |
| Jeremy Lavy Frcs Medical Ltd | Health & social care | 2025 |
| Jeremy Neeves Garden Designs Ltd | Administrative & support | 2024 |
| Jermyn Motor Group Limited | Wholesale & retail | 1972 |
| Jerome LIM Limited | Health & social care | 2023 |
| Jerome Shorter Furniture Limited | Manufacturing | 2019 |
| Jessica’S Boutique Limited | Wholesale & retail | 2019 |
| Jessmima Ltd | Administrative & support | 2016 |
| Jestic UK Bidco Limited | Financial services | 2019 |
| Jestic UK Holdco Limited | Financial services | 2019 |
| JET Heating Ltd | Construction | 2021 |
| JFA Systems Limited | Information & communication | 1990 |
| Jfc's Fast Food (Hailsham) Limited | Administrative & support | 2005 |
| Jfc's Fast Food (Tunbridge Wells) Ltd | Administrative & support | 2011 |
| JFS Roofing & Cladding Ltd | Construction | 2009 |
| JH Estate and Garden Services Limited | Administrative & support | 2022 |
| JHC Building Services Ltd | Construction | 2018 |
| JHG Management Limited | Households | 2025 |
| JHS Gears Limited | Manufacturing | 2015 |
| Jhsr Consultancy Ltd | Professional & scientific | 2021 |
| Jhutt Financial Group Limited | Professional & scientific | 2026 |
| JIM Knight & Sons Isle of Oxney Limited | Construction | 2015 |
| Jimini Graphics Limited | Extraterritorial | 1994 |
| Jinky's Corner Ltd | Wholesale & retail | 2025 |
| JJM Management (Kent) Limited | Manufacturing | 2021 |
| JJP Contracts Ltd | Construction | 2019 |
| Jknight Electrical Services Limited | Extraterritorial | 2026 |
| JLH Medical Ltd | Health & social care | 2019 |
| JLM Civil Engineering (UK) Limited | Construction | 2012 |
| JLM Investment Portfolio Limited | Real estate | 2013 |
| JLR Holdings Limited | Professional & scientific | 2005 |
| JMB Building Material Services Limited | Professional & scientific | 2023 |
| JME Development Management LLP | | 2019 |
| JMF Interiors (Kent) Limited | Construction | 2015 |
| Jmik Ltd | Transport & logistics | 2025 |
| Jmlw Dermatology Limited | Health & social care | 2017 |
| JNH Property Ltd | Real estate | 2016 |
| Joanne Warner Consulting Ltd | Information & communication | 2024 |
| Joarder Diagnostics Ltd | Health & social care | 2021 |
| Jobs Plus Ltd | Administrative & support | 2017 |
| John Bennett & Co (Billiards & Sports) Limited | Manufacturing | 2010 |
| John Bennett (Billiards) Ltd | Manufacturing | 2005 |
| John D Hoad Limited | Professional & scientific | 2002 |
| John Dobing Consultants Limited | Professional & scientific | 2002 |
| John Knowles Builders Ltd | Construction | 2005 |
| John Newton & Company Limited | Wholesale & retail | 1927 |
| John Newton (Developments) Limited | Real estate | 1964 |
| John Newton Developments (Holdings) Limited | Real estate | 2016 |
| John Perkins Associates Ltd | Professional & scientific | 2019 |
| John Steward Transport Limited | Transport & logistics | 1981 |
| John Tyler Properties Limited | Real estate | 1972 |
| Johnson Exterior Cleaning Ltd | Administrative & support | 2025 |
| Joinerysupply Ltd | Wholesale & retail | 2026 |
| Jonal Enterprises Limited | Hospitality | 2012 |
| Jonal Lifestyle Limited | Hospitality | 2012 |
| Jonathan Reynolds Limited | Professional & scientific | 2025 |
| Jore Consultancy Ltd | Real estate | 2021 |
| Joseph Plumbing Limited | Construction | 2021 |
| Joshi SAN Consulting Ltd | Professional & scientific | 2024 |
| Jovella Ltd | Professional & scientific | 2023 |
| Joyride Media Ltd | Administrative & support | 2017 |
| JP Infotech Ltd | Information & communication | 2025 |