| JMP Scaffold Supplies & Hire Limited | Administrative & support | 2022 |
| JMR Property Maintenance Ltd | Construction | 2002 |
| JMT Embroidery Ltd | Wholesale & retail | 2013 |
| JNJ Media Ltd | Information & communication | 2024 |
| JNS Property Services Ltd | Construction | 2018 |
| JOA Installers Limited | Construction | 2022 |
| Joanna Parker Limited | Information & communication | 2019 |
| Jodie Clark Limited | Arts & recreation | 2016 |
| JOE Jenkins Limited | Information & communication | 2020 |
| John and Ginger Limited | Wholesale & retail | 2009 |
| John Aprax Ltd | Transport & logistics | 2017 |
| John Brown Restoration Limited | Wholesale & retail | 2012 |
| John Collinge (Civil Engineering) Limited | Construction | 1998 |
| John Daniel Enterprises Limited | Professional & scientific | 2023 |
| John Gillam Associates Limited | Professional & scientific | 2015 |
| John Horwood Consultants Limited | Administrative & support | 1976 |
| John Howard Mortgages Ltd | Financial services | 2011 |
| John Humphrey Limited | Administrative & support | 2017 |
| John Hunnisett & Associates Ltd | Wholesale & retail | 2019 |
| John Lower (Developments) Limited | Construction | 1973 |
| John Mitchell Racing Limited | Wholesale & retail | 2013 |
| John Mossop (Farmers) Limited | Professional & scientific | 1952 |
| John O'Donnell Engineering Limited | Professional & scientific | 2023 |
| John Vickers Limited | Real estate | 1933 |
| Johnny Swedish Limited | Professional & scientific | 2015 |
| Johnsons Plastering Ltd | Construction | 2025 |
| Jolliman Limited | Real estate | 1981 |
| Jolyon Nash Consulting Limited | Professional & scientific | 2021 |
| JON Allen Design Limited | Professional & scientific | 2001 |
| JON Blake Consultants Ltd | Construction | 2004 |
| JON Taylor Limited | Information & communication | 1997 |
| JON Wadey & Co Limited | Construction | 2009 |
| Jon'Ll FIX IT Limited | Other services | 2009 |
| Jonathan Davis Wealth Management Ltd | Financial services | 2006 |
| Jonathan Ings Structural Engineer Ltd | Professional & scientific | 2025 |
| Jones Avens Limited | Extraterritorial | 2006 |
| Jonjon Limited | Professional & scientific | 2023 |
| Jooles Holdings Limited | Professional & scientific | 1996 |
| Jord Hammond Photography Ltd | Professional & scientific | 2019 |
| Jord Hammond's Academy of Photography Ltd | Education | 2020 |
| Jordan & Cook Limited | Real estate | 1991 |
| Jordan Messoud's UK Properties Limited | Real estate | 2024 |
| Joseph Building Surveying Ltd | Other services | 2022 |
| Joseph John Ltd | Construction | 2014 |
| Joseph MAY Ltd | Real estate | 2026 |
| Journey Within Therapeutic Coaching Limited | Health & social care | 2024 |
| Joy Riders LLP | | 2024 |
| JP Clinician Limited | Other services | 2018 |
| JP20 Limited | Real estate | 2022 |
| JPB Holding Ltd | Financial services | 2019 |
| JPR Drylining Ltd | Construction | 2015 |
| JPS Refurbs Limited | Construction | 2022 |
| JR Property Group (Sussex) Limited | Real estate | 2002 |
| JRB (Hants) Holdings Limited | Financial services | 2024 |
| JRH Landscapes Limited | Administrative & support | 2012 |
| JRM Carpentry Limited | Construction | 2017 |
| JRM Gold Rush Ltd | Wholesale & retail | 2023 |
| Jrprestige Limited | Wholesale & retail | 2016 |
| JRV Engineering Ltd | Manufacturing | 2011 |
| JS Build Ltd | Construction | 2019 |
| JS Byrne Holdings Ltd | Financial services | 2024 |
| JS International Holding Limited | Financial services | 2020 |
| JS PUB Management Ltd | Hospitality | 2024 |
| JS Stunts Ltd | Arts & recreation | 2014 |
| JSB Accommodation Ltd | Hospitality | 2024 |
| JSB MET Training Ltd | Education | 2024 |
| JSB Structures Ltd | Administrative & support | 2021 |
| JSD Prestige Ltd | Wholesale & retail | 2020 |
| Jshd Ltd | Real estate | 2025 |
| JSM Driving School Ltd | Education | 2016 |
| Jsmarketinglife Ltd | Professional & scientific | 2018 |
| JSR Group Limited | Manufacturing | 2023 |
| JT Plumbing & Heating Limited | Construction | 2015 |
| JTL Properties Limited | Real estate | 2016 |
| JTN Creative Holding Limited | Information & communication | 2025 |
| Jude Films Ltd | Information & communication | 2020 |
| Judge Scaffolding Ltd | Construction | 2025 |
| Juicy Car Care Ltd | Wholesale & retail | 2021 |
| Juicy Details Limited | Wholesale & retail | 2010 |
| Juicy Sweets Limited | Wholesale & retail | 2020 |
| Jukeyz Limited | Arts & recreation | 2020 |
| Jules Haley Counselling & Psychotherapy Limited | Health & social care | 2026 |
| Julia Davies Ltd | Information & communication | 2021 |
| Julian Church & Associates Property Holdings Limited | Real estate | 2020 |
| Julie James Hypnotherapy Limited | Other services | 2013 |
| Julien Matthew Property Limited | Real estate | 2025 |
| Jumeirah Consulting Group Limited | Professional & scientific | 2025 |
| Jump Start Jonny Ltd | Other services | 2023 |
| Jumpstart Design Ltd | Arts & recreation | 2018 |
| Jumpstart Interactive Limited | Information & communication | 2014 |
| Juntos Baby Massage Ltd | Health & social care | 2024 |
| Jupps Limited | Professional & scientific | 2004 |
| Jupps Properties Ltd | Real estate | 2019 |
| Jupps Removals and Storage Ltd | Administrative & support | 2019 |
| Just Chef Jobs Limited | Administrative & support | 2015 |
| Just Mowing Limited | Administrative & support | 2010 |
| Justice & Co Commercial Limited | Real estate | 2022 |
| Justice & Co Property Management Limited | Real estate | 2022 |
| Justice & Co Residential Limited | Real estate | 2026 |
| Justtouch Limited | Information & communication | 2010 |