| J&S Snaax Ltd | Wholesale & retail | 2021 |
| J&S UK Logistics Ltd | Transport & logistics | 2023 |
| J&T Ground Work and Roofing Ltd | Construction | 2025 |
| J&Y&L Limited | Information & communication | 2017 |
| J'S Finsight Consulting Limited | Professional & scientific | 2025 |
| J. L. O'Rourke & Sons Limited | Construction | 1971 |
| J.A.M. Sharma Ltd | Real estate | 2013 |
| J.Bibihousing Ltd | Real estate | 2025 |
| J.D. Hartley and Co. Ltd. | Extraterritorial | 2009 |
| J.I.A.R Ltd | Wholesale & retail | 2023 |
| J.L.O'Rourke (Construction) Limited | Construction | 1977 |
| J.Laver Consulting Ltd | Education | 2020 |
| J.N Property Referrals Limited | Real estate | 2015 |
| J.N. Systems Limited | Administrative & support | 2021 |
| J.Oakes & SON Skip Hire Ltd | Water & waste | 2017 |
| J.P.Mcdougall & Co.Limited | Wholesale & retail | 1931 |
| J.R Recovery Ltd | Transport & logistics | 2025 |
| J.W. Spear & Sons Limited | Extraterritorial | 1930 |
| J13 Investments Ltd | Real estate | 2024 |
| J2K Technologies Limited | Information & communication | 2014 |
| J4J Services Ltd | Construction | 2025 |
| J8 Mechanical Ltd | Construction | 2021 |
| Jaan Group Ltd | Water & waste | 2025 |
| Jaan Sher.Co Ltd | Wholesale & retail | 2025 |
| Jaap Malhi Ltd | Construction | 2024 |
| JAB Props Ltd | Real estate | 2025 |
| Jaba Express Limited | Transport & logistics | 2021 |
| Jabaz Ltd | Wholesale & retail | 2025 |
| Jabba Engineering Ltd | Wholesale & retail | 2017 |
| Jabbalbibra Property Management Ltd | Real estate | 2025 |
| Jacd Property Ltd | Construction | 2026 |
| Jachak Construction Ltd | Construction | 2025 |
| Jacinthe Rayner Limited | Wholesale & retail | 1934 |
| Jack Andrews Enterprises Ltd | Education | 2019 |
| Jack Exec Ltd | Information & communication | 2025 |
| Jack Pearton Ltd | Information & communication | 2021 |
| Jackson O'Rourke Estate Agents Limited | Real estate | 2015 |
| Jackson Prescott Limited | Real estate | 2001 |
| Jacob Cars UK Ltd | Wholesale & retail | 2024 |
| Jacob Luscombe Design Limited | Professional & scientific | 2024 |
| Jacobs & Co Transport Ltd | Transport & logistics | 2018 |
| JAD Developments (Redruth) Ltd | Real estate | 2016 |
| JAD Developments UK Limited | Real estate | 2011 |
| Jadour Limited | Wholesale & retail | 2021 |
| JAF Executive Travels Limited | Transport & logistics | 2014 |
| JAF Logistic Solutions Ltd | Transport & logistics | 2021 |
| JAF Worldwide Executive Travels Ltd | Transport & logistics | 2021 |
| Jaffary & Co Holdings Ltd | Financial services | 2026 |
| Jaffary Property Investments Ltd | Real estate | 2025 |
| JAG Contractor Ltd | Construction | 2023 |
| Jagar Enterprises Limited | Energy | 2012 |
| Jagdish Singh Ltd | Construction | 2019 |
| Jaggi's Final Touch Hair and Beauty Studio Ltd | Other services | 2017 |
| Jagir Property Ltd | Real estate | 2025 |
| Jags IT Solutions Limited | Information & communication | 2020 |
| JAH Investments Holdings Ltd | Real estate | 2022 |
| Jahid Ltd | Construction | 2025 |
| JAI DEV Nasib Properties Ltd | Real estate | 2025 |
| Jaikara Limited | Hospitality | 2026 |
| Jakeesan Ltd | Construction | 2012 |
| Jakub Starski Limited | Transport & logistics | 2025 |
| Jalaluddin Holdings Limited | Real estate | 2017 |
| Jalbani Implex Private Ltd | Wholesale & retail | 2025 |
| JAM JAR Estates Limited | Real estate | 2019 |
| Jambo Services Limited | Households | 2024 |
| Jamel Construction Ltd | Construction | 2025 |
| James Collins Ltd | Other services | 2022 |
| James Corner Field Operations Limited | Professional & scientific | 2012 |
| James Daniel London Limited | Construction | 2023 |
| James Elliman Homes Limited | Real estate | 2017 |
| James Wood International Ltd | Real estate | 2015 |
| Jammy-Tech Ltd. | Wholesale & retail | 2007 |
| Jamo Consulting Ltd | Professional & scientific | 2025 |
| JAN Japan Hybrid Motors Limited | Transport & logistics | 2019 |
| JAN Transport Ltd | Transport & logistics | 2025 |
| Janah Funeral Services Ltd | Other services | 2023 |
| Jananysp Ltd | Health & social care | 2025 |
| Jane Energy Cleaning Limited | Administrative & support | 2017 |
| Janet Hoor Ltd | Wholesale & retail | 2023 |
| Janjua & Co Accountants Ltd | Professional & scientific | 2020 |
| Jankiewicz Property Ltd | Real estate | 2022 |
| Janm Ltd | Transport & logistics | 2021 |
| Jannat Beauty Limited Limited | Other services | 2014 |
| Jannat Co. Ltd | Hospitality | 2010 |
| Janta Management Limited | Transport & logistics | 2004 |
| Janus Investments Limited | Professional & scientific | 2009 |
| Janzo Properties LLP | | 2017 |
| JAO Proco Limited | Real estate | 2016 |
| JAP Motor Cars Ltd | Wholesale & retail | 2023 |
| JAP Store Ltd | Wholesale & retail | 2023 |
| Japa UK Limited | Administrative & support | 2022 |
| Japco Ltd | Extraterritorial | 2023 |
| Japp Haulage Ltd | Transport & logistics | 2023 |
| Jaradeh & Chammas Ltd | Financial services | 2018 |
| Jard Construction Limited | Construction | 2017 |
| Jarpjb LLP | | 2013 |
| Jarra Enterprises Ltd | Wholesale & retail | 2025 |
| Jarwaste Ltd | Water & waste | 2025 |
| JAS Constructions Slough Ltd | Construction | 2014 |
| JAS Electrical & Security Services Ltd | Construction | 2017 |