| Jade M&E Services Limited | Construction | 2021 |
| Jaeger Retail Limited | Wholesale & retail | 2017 |
| Jaffrey Management Limited | Arts & recreation | 2006 |
| Jaiy Engineering Consultancy Limited | Professional & scientific | 2025 |
| Jakarta Coal Exchange Limited | Professional & scientific | 2025 |
| JAM & KT Property Services Limited | Hospitality | 2025 |
| JAM Design Works Limited | Professional & scientific | 2021 |
| JAM Pact NO.1 Ltd | Real estate | 2017 |
| JAM Pact NO.2 Ltd | Real estate | 2017 |
| Jamech (UK) Limited | Energy | 2014 |
| James Building Contractors Limited | Construction | 2004 |
| James Cadby Creative Ltd | Professional & scientific | 2018 |
| James Global Consultancy Limited | Professional & scientific | 2021 |
| James Henry Consultancy Ltd | Financial services | 2021 |
| James Interiors Limited | Construction | 2021 |
| Jameston Limited | Other services | 1986 |
| Jamjar Real Estate Ltd | Real estate | 2022 |
| Jamloch Records Limited | Information & communication | 2021 |
| Jammie Management Limited | Extraterritorial | 2005 |
| Janet Frances Ryan Limited | Professional & scientific | 2020 |
| Jardine Electrical Contractors Ltd | Construction | 2018 |
| Jasmine Flowers Shenfield Ltd. | Wholesale & retail | 2014 |
| Jason Court Limited | Households | 2001 |
| Jasper Ilustra Ltd | Other services | 2024 |
| JAT & DJT Investments Limited | Real estate | 2022 |
| Javero Property Limited | Construction | 2021 |
| Javex Consulting Ltd | Information & communication | 2010 |
| Jawdan Associates Ltd. | Information & communication | 1998 |
| JAX Technologies Limited | Information & communication | 2026 |
| Jaxx Paris Ltd | Other services | 2019 |
| Jaycock & SON Limited | Construction | 2015 |
| Jaycode Developments Limited | Real estate | 2015 |
| Jaycode Ltd | Real estate | 2004 |
| Jaycode Trading Company Ltd | Construction | 2022 |
| Jaydee Properties Limited | Real estate | 2016 |
| Jayel Consulting Limited | Transport & logistics | 2023 |
| JBL Electrical Ltd | Energy | 2023 |
| JBL Tech Limited | Information & communication | 2008 |
| JBR Mechanical Services Limited | Construction | 2025 |
| JC K9 Security Ltd | Administrative & support | 2025 |
| JC Publishing Ltd | Information & communication | 2011 |
| JC Reigns Bible School Ltd | Education | 2020 |
| JD Bird Construction Ltd | Construction | 2025 |
| JD Classics Autos Ltd | Manufacturing | 2022 |
| JD Design & Landscapes Limited | Construction | 2025 |
| Jdar Assets Ltd | Real estate | 2020 |
| JDB Developments Ltd | Households | 2019 |
| JDC Fencing Limited | Construction | 2023 |
| JDE Property Ltd | Real estate | 2020 |
| JDL Trading Ltd | Arts & recreation | 2025 |
| JDM Acquisitions Limited | Real estate | 2023 |
| JDM Garden Maintenance Ltd | Administrative & support | 2020 |
| Jdmd Management Ltd | Administrative & support | 2021 |
| Jdpiperco Ltd | Professional & scientific | 2024 |
| JDR Trans Ltd | Transport & logistics | 2016 |
| JDS Projects Ltd | Professional & scientific | 2017 |
| JDW Investments Limited | Financial services | 2019 |
| Jeffcote Donnison LLP | | 2002 |
| Jelly Bean Events Limited | Arts & recreation | 2015 |
| JEM Professional Services Limited | Professional & scientific | 2025 |
| Jenkins Estates 2 Limited | Real estate | 2025 |
| Jenkins Estates Ltd | Real estate | 2020 |
| Jenkins Property Lettings Ltd | Real estate | 2025 |
| Jenkins Property Limited | Real estate | 2026 |
| Jenkins Property Sales Ltd | Real estate | 2025 |
| Jenkins Proptech Media Ltd | Professional & scientific | 2019 |
| Jenny's Nails & Beauty (CM) Limited | Other services | 2022 |
| Jerome Engineering Limited | Manufacturing | 1975 |
| Jerry Flaxman Consulting Limited | Financial services | 2012 |
| Jessicalo Ltd | Administrative & support | 2023 |
| Jesson Cupcakes Limited | Manufacturing | 2011 |
| JET Contracts Ltd | Professional & scientific | 2020 |
| JET Solutions South Ltd | Professional & scientific | 2015 |
| Jewel of Holistics Ltd | Other services | 2023 |
| JFB Collaborative Consulting Ltd | Professional & scientific | 2025 |
| JFP Vehicle Sales & Sourcing Ltd | Administrative & support | 2022 |
| JG Domestic Services Limited | Other services | 2025 |
| JGK Claims Services Limited | Professional & scientific | 2019 |
| JH Cleaning & Support Services Limited | Administrative & support | 2010 |
| JH Direct Limited | Administrative & support | 2024 |
| Jhead Installations Ltd | Construction | 2018 |
| Jigsaw Recruiting Holdings Limited | Financial services | 2025 |
| Jigsaw Recruiting Ltd | Professional & scientific | 2005 |
| Jigsaw Retirement Solutions Limited | Real estate | 2012 |
| Jivestar Limited | Financial services | 1981 |
| JJ1 Property Limited | Financial services | 2025 |
| JJB Electrical Services Ltd | Construction | 2022 |
| JJB Waste Ltd | Water & waste | 2022 |
| JJE Property Ltd | Real estate | 2014 |
| Jjl&G Limited | Real estate | 2021 |
| JJT Retail Solutions Limited | Professional & scientific | 2010 |
| JK Electrical (Hornchurch) Limited | Construction | 2015 |
| Jkarth Limited | Hospitality | 2024 |
| Jkba Ltd | Professional & scientific | 2015 |
| JKF Plumbing and Heating Ltd | Construction | 2017 |
| JL Motors Services Ltd | Wholesale & retail | 2023 |
| JLR Solutions Associates Ltd | Other services | 2016 |
| Jmbconsult Ltd | Professional & scientific | 2009 |
| JMC &PMC. Health Ltd | Other services | 2024 |
| Jmda Property Limited | Real estate | 2025 |