| Isom Management Limited | Real estate | 2006 |
| IT Harbour Ltd | Information & communication | 2026 |
| It's GOT Legs Bespoke Furniture and Building Services Limited | Manufacturing | 2026 |
| Italy Imported Ltd | Wholesale & retail | 2013 |
| Itchenor Yacht Club Limited | Real estate | 2011 |
| Iter Fide Limited | Real estate | 2022 |
| ITL Consultancy Ltd | Professional & scientific | 2020 |
| J & R Press Limited | Administrative & support | 2010 |
| J Austin Properties Limited | Real estate | 2026 |
| J Beadle Engineering Ltd | Professional & scientific | 2014 |
| J Butler Bespoke Ltd | Wholesale & retail | 2022 |
| J C C Lighting Holdings Limited | Financial services | 2013 |
| J C C Lighting Products Limited | Manufacturing | 1995 |
| J C Portable Site Accommodation Ltd | Construction | 2011 |
| J C Solicitors Limited | Professional & scientific | 2010 |
| J Conwell Agricultural Services & Groundworks Ltd | Other services | 2024 |
| J H Burley Limited | Professional & scientific | 2003 |
| J Henry Agincourt Ltd | Real estate | 1980 |
| J Holden Construction Ltd | Construction | 2024 |
| J Irving Engineering Services Limited | Wholesale & retail | 2018 |
| J Key Leisure Ltd | Hospitality | 2006 |
| J M Davis Installations Ltd | Construction | 2015 |
| J M Fletcher Consulting Limited | Financial services | 2012 |
| J M G (Southern) Limited | Wholesale & retail | 1986 |
| J Murphy Electrical Limited | Construction | 2015 |
| J Prudence Consulting Limited | Administrative & support | 2014 |
| J R B Environmental Limited | Professional & scientific | 2008 |
| J S Dalton Limited | Construction | 2006 |
| J S Oxford Services Ltd | Wholesale & retail | 2025 |
| J&B Endeavours Limited | Hospitality | 2018 |
| J&M Cardiology Services Ltd | Professional & scientific | 2025 |
| J, S & M Trading Limited | Extraterritorial | 2025 |
| J. Alan Properties Limited | Construction | 2004 |
| J. Salbstein | Real estate | 1950 |
| J.A.M. Electrical Solutions Ltd | Construction | 2014 |
| J.A.S.A. Solutions Ltd | Professional & scientific | 2014 |
| J.H.& F.W.Green Limited | Agriculture & fishing | 1917 |
| J.P. Searle Contract Services Ltd | Construction | 2021 |
| J.R.Hansford Limited | Wholesale & retail | 1955 |
| J2T Properties Ltd | Real estate | 2017 |
| J5 Consulting Limited | Professional & scientific | 2012 |
| JA PA Services Limited | Other services | 2008 |
| Jacaranda Tree Limited | Professional & scientific | 2016 |
| Jack & Co U.K Ltd | Wholesale & retail | 2021 |
| Jack of Hearts INK Ltd | Arts & recreation | 2022 |
| Jackson & Co Developments Ltd | Construction | 2025 |
| Jacobs Carpentry Ltd | Manufacturing | 2017 |
| Jake Smith Landscapes Limited | Administrative & support | 2017 |
| Jalla Management Partners Limited | Hospitality | 2024 |
| Jamaza Ltd | Information & communication | 2025 |
| Jamco Events Ltd | Hospitality | 2025 |
| James & Sons Roofing Ltd | Construction | 2020 |
| James Fleming Properties Limited | Real estate | 2022 |
| James Todd & Co Limited | Professional & scientific | 2010 |
| James Wells Architectural Services Limited | Extraterritorial | 2018 |
| Jamie Mitchell Technologies Limited | Administrative & support | 2007 |
| Jamjar Property Management Ltd. | Households | 2015 |
| Jane Bulbeck Ltd | Other services | 2018 |
| Jane Bulbeck Skincare & Beauty Ltd | Other services | 2025 |
| Jane Bulbeck Yoga Ltd | Health & social care | 2022 |
| Jansen Holdings Limited | Financial services | 2021 |
| Japanese Futons Ltd | Wholesale & retail | 2014 |
| Japeto Ltd | Wholesale & retail | 2011 |
| Jardiner Ltd | Administrative & support | 2019 |
| Jason Court Residents Association Ltd. | Households | 1997 |
| Jasper the Dog Walker Ltd | Information & communication | 2016 |
| JAX687 Limited | Arts & recreation | 2020 |
| Jaxx Sussex Ltd. | Other services | 2014 |
| JAY Property Management Limited | Construction | 2015 |
| Jayview Estates Limited | Real estate | 1972 |
| Jaywalk Communication Limited | Administrative & support | 2022 |
| Jbgb Holdings Ltd | Financial services | 2025 |
| Jblamire 2 Ltd | Arts & recreation | 2022 |
| Jbms Developments Ltd | Construction | 2012 |
| JBO (UK) Limited | Real estate | 2012 |
| JBR Services Ltd | Administrative & support | 2025 |
| JBS Design and Build Limited | Construction | 2013 |
| Jbscaterers Ltd | Hospitality | 2026 |
| JC Human Resources Ltd | Professional & scientific | 2004 |
| JCA Creative Ltd | Professional & scientific | 2000 |
| JCH Rentals Ltd | Real estate | 2023 |
| JCK Lettings Limited | Real estate | 2020 |
| JCK Property Holdings Limited | Financial services | 2024 |
| JCK Property Lettings Limited | Real estate | 2022 |
| JCS Carpentry & Building Ltd | Construction | 2024 |
| JCS Carpentry Limited | Construction | 2016 |
| Jddr Capital Limited | Other services | 2024 |
| JDJ Sporting Clays Ltd | Arts & recreation | 2022 |
| JDM Detailing Ltd | Administrative & support | 2025 |
| Jdrs Consulting Limited | Professional & scientific | 2020 |
| Jeff MC Ltd | Manufacturing | 2017 |
| Jeffrey Webb Limited | Professional & scientific | 2015 |
| Jeffries Healthcare Limited | Financial services | 2026 |
| Jelipop Holdings Ltd | Financial services | 2024 |
| Jennings & Co Financial Planning Limited | Financial services | 2018 |
| Jeppesen & Pons Ltd | Professional & scientific | 2021 |
| Jerboa Homes Ltd | Construction | 2019 |
| JES Editorial Limited | Administrative & support | 2011 |
| JES Homes Ltd | Real estate | 2024 |
| Jestico's Close Management Company Limited | Households | 2008 |