| James Developments (Brighton) Limited | Construction | 2013 |
| James Hall Design Ltd | Professional & scientific | 2020 |
| James K. Ltd | Professional & scientific | 2014 |
| James Newton Ltd | Information & communication | 2009 |
| Jamil Medical Limited | Professional & scientific | 2015 |
| Jamildent Limited | Health & social care | 2018 |
| Jane Lyons Research Management & Consultancy Limited | Professional & scientific | 2002 |
| Jane Waterman Consulting Ltd | Professional & scientific | 2017 |
| Jangra Lets Limited | Real estate | 2021 |
| Jard Design Ltd | Professional & scientific | 2017 |
| Jardine Property Limited | Real estate | 2013 |
| Jarman Brand Marketing Ltd | Professional & scientific | 2026 |
| Jasmine Consultancy Limited | Professional & scientific | 2025 |
| Jason Baker Limited | Manufacturing | 2002 |
| Jason Downer Limited | Manufacturing | 2019 |
| JAT Advisors Ltd | Professional & scientific | 2012 |
| Javg Ltd | Administrative & support | 2026 |
| Jaxmar Limited | Wholesale & retail | 2015 |
| JAY Bros. Limited | Real estate | 2008 |
| JAY Okafor Security Limited | Other services | 2018 |
| Jaydane Property Finance Limited | Financial services | 2002 |
| Jaypost Property Management Company Limited | Professional & scientific | 1991 |
| Jays Newsagent Limited | Wholesale & retail | 2009 |
| Jazab Limited | Health & social care | 2019 |
| JB Decorating Ltd | Construction | 2015 |
| JB Dental Services Limited | Health & social care | 2016 |
| JB SPV1 Ltd | Real estate | 2024 |
| JB SPV3 Ltd | Financial services | 2024 |
| JB SPV4 Limited | Construction | 2025 |
| JB SPV8 Ltd | Real estate | 2025 |
| JB SPV9 Ltd | Real estate | 2025 |
| JBA Estates Limited | Real estate | 2019 |
| Jbcb Property Limited | Real estate | 2021 |
| JBV Properties Ltd | Real estate | 2022 |
| JC ALL Electrical Ltd | Construction | 2025 |
| JC Apps Limited | Information & communication | 2017 |
| Jccl Holdings Ltd | Financial services | 2020 |
| JCE Services Limited | Information & communication | 2007 |
| JCG Empire Limited | Real estate | 2020 |
| JCG Muscovy Ltd | Real estate | 2025 |
| JCK Marketing Limited | Administrative & support | 2010 |
| Jclw Consulting Ltd | Information & communication | 2022 |
| Jcoo Solutions Limited | Administrative & support | 2026 |
| JD Turbine Services Limited | Manufacturing | 2023 |
| JDA Capital Ltd | Financial services | 2024 |
| Jda.Hospitality Ltd | Hospitality | 2023 |
| JDM Wholesale Limited | Wholesale & retail | 2025 |
| Jdnt Ltd | Professional & scientific | 2024 |
| Jecain Limited | Financial services | 2019 |
| JED Stemp Ltd | Construction | 2017 |
| JEE Bazzle Ltd | Information & communication | 2020 |
| Jelldy Investments Limited | Real estate | 2017 |
| Jellyfish Consulting Ltd | Information & communication | 2023 |
| Jenny King Embroidery Limited | Manufacturing | 2013 |
| Jenya Dental Care Limited | Health & social care | 2025 |
| Jerjees Limited | Real estate | 2026 |
| Jermayne Williams Limited | Arts & recreation | 2020 |
| Jesmond Capital Limited | Professional & scientific | 2016 |
| Jesmond Property Investments Limited | Real estate | 2024 |
| Jess Bouman Ltd. | Administrative & support | 2018 |
| Jess Moloney Mgmt Limited | Other services | 2017 |
| Jessica Dellow Ltd | Arts & recreation | 2023 |
| Jestholm Limited | Financial services | 2026 |
| JET A2B Fuels Ltd | Other services | 2014 |
| Jetnine 23 Limited | Financial services | 2016 |
| Jfms Management Ltd | Households | 2023 |
| JG & JR Langridge Limited | Construction | 2010 |
| JG Vkengineering Ltd | Professional & scientific | 2021 |
| JGB International Limited | Wholesale & retail | 2018 |
| JGB Property Limited | Real estate | 2014 |
| JHB Accountancy and Tax Services Ltd | Professional & scientific | 2017 |
| JIA Health Ltd | Health & social care | 2025 |
| JIA Property Design & Management Ltd | Real estate | 2023 |
| Jidapha's Spa Treatments & Therapies Ltd | Other services | 2006 |
| Jiggers Limited | Manufacturing | 1990 |
| Jigsaw Business Solutions Ltd | Administrative & support | 2013 |
| Jimeki Holdings Limited | Professional & scientific | 2025 |
| JIN Acupuncture Ltd | Health & social care | 2024 |
| JIN Designs Ltd | Professional & scientific | 2013 |
| Jits Transport Ltd | Transport & logistics | 2019 |
| Jiva Healthcare Limited | Health & social care | 2007 |
| JJ Ockenden Limited | Manufacturing | 2002 |
| Jkface Limited | Health & social care | 2024 |
| Jkrl Limited | Professional & scientific | 2022 |
| JKW Projects Ltd | Professional & scientific | 2015 |
| JL Lynch Holdings Ltd | Real estate | 2025 |
| JL Shutters Limited | Wholesale & retail | 2017 |
| JLC Law Ltd | Professional & scientific | 2025 |
| Jlhcc Holdings Limited | Financial services | 2019 |
| JLP Holdings (Sussex) Ltd | Financial services | 2025 |
| Jlvo French Real Estate Consulting Limited | Professional & scientific | 2023 |
| JLW Woodworks Ltd | Construction | 2017 |
| JM Car Services Ltd | Wholesale & retail | 2022 |
| JM Osteopathy & Wellbeing Ltd | Extraterritorial | 2024 |
| JM Specialists Ltd | Health & social care | 2025 |
| JMA Property Maintenance Ltd | Construction | 2011 |
| Jmcb AOD Ltd | Health & social care | 2009 |
| Jmcp Ltd | Real estate | 2024 |
| JMD Property Management Limited | Real estate | 2021 |
| Jmdent Limited | Health & social care | 2021 |