| J Scott Installations Ltd | Construction | 2015 |
| J&A Builds Ltd | Construction | 2024 |
| J&B Property & Developments Ltd | Real estate | 2024 |
| J&D Landscape Services Limited | Administrative & support | 2019 |
| J&R Logistics Ltd | Transport & logistics | 2019 |
| J. Munter Consulting Ltd | Professional & scientific | 2022 |
| J. Wootton Carpentry Limited | Construction | 1997 |
| J.M.H. Joinery Limited | Wholesale & retail | 1973 |
| J.P.B. Electrical Limited | Construction | 2004 |
| J.R Oak Ltd | Administrative & support | 2020 |
| J.T. Barnes Electrical Limited | Construction | 2015 |
| J.T. Barnes Limited | Extraterritorial | 2007 |
| J.W.Daynes Paint Finishers Ltd | Other services | 2010 |
| J1 Surveying Limited | Professional & scientific | 2022 |
| J3DA Ltd | Health & social care | 2023 |
| J3S Ltd | Real estate | 2025 |
| Jaber Investments Ltd | Real estate | 2021 |
| Jack Sharpe Property Investments Limited | Administrative & support | 2003 |
| Jackal Enterprises Limited | Agriculture & fishing | 1980 |
| Jackson & SON Site Services Ltd | Construction | 2022 |
| Jacob the Barber Ltd | Other services | 2023 |
| Jacobs Faith in Property Ltd | Real estate | 2019 |
| Jacqson Diego Story Emporium Limited | Wholesale & retail | 2011 |
| JAG Rigging Solutions Ltd | Information & communication | 2017 |
| Jaletprivate Limited | Real estate | 2018 |
| Jalexr Ltd | Financial services | 2025 |
| James Buckland Limited | Wholesale & retail | 2002 |
| James Charles Interiors Limited | Construction | 2022 |
| James Martin Food Events Ltd | Hospitality | 2024 |
| James&Sonny Transport Ltd | Transport & logistics | 2026 |
| Janice Properties Ltd | Real estate | 2020 |
| Janna Spannagel Coaching Ltd | Education | 2020 |
| Jatemen Limited | Professional & scientific | 2022 |
| JAY Thain Ltd | Financial services | 2023 |
| JAY Vowell Ltd | Other services | 2011 |
| Jaybest Limited | Professional & scientific | 2022 |
| Jaytee Skip Hire Limited | Water & waste | 2016 |
| JB Farming Essex Ltd | Agriculture & fishing | 2020 |
| JB Psychiatry Ltd | Health & social care | 2026 |
| JB Services (Essex) Limited | Construction | 2015 |
| JBS Building Solutions Ltd | Construction | 2023 |
| JC & BC Electrical Ltd | Construction | 2022 |
| JC Air Conditioning Services Ltd | Construction | 2023 |
| JC Stirling Property Limited | Real estate | 2022 |
| JCB Estates (SW) Ltd | Construction | 2025 |
| JCS Grab Hire Ltd | Construction | 2024 |
| JD Properties Group Ltd | Real estate | 2025 |
| JDB Utilities Ltd | Construction | 2022 |
| JDC Ceilings and Partitions Ltd | Construction | 2021 |
| JDJ Developments Ltd | Construction | 2024 |
| JDK Communications Ltd | Construction | 2023 |
| JDL Secretariat Limited | Administrative & support | 2017 |
| JDM Developments (Essex) Limited | Construction | 2012 |
| JDM Holdings (Essex) Limited | Financial services | 2024 |
| JDM Properties (Essex) Limited | Real estate | 2024 |
| JDP Financial Enterprise Limited | Professional & scientific | 2016 |
| JE Diagnostics Ltd | Health & social care | 2023 |
| JEA Properties Limited | Real estate | 2019 |
| JEL Assets Ltd | Financial services | 2019 |
| Jellaka Consultancy Limited | Professional & scientific | 2015 |
| Jenmoore Holdings Ltd | Real estate | 2023 |
| Jenner AM Ltd | Real estate | 2021 |
| JET Tyres Limited | Wholesale & retail | 1989 |
| Jfdi Consultants Limited | Professional & scientific | 2007 |
| JH Construct Ltd | Construction | 2025 |
| Jhartiemanagementcompany Ltd | Real estate | 2018 |
| JHD Dwellings Limited | Construction | 2023 |
| Jhsolar Limited | Construction | 2025 |
| JI & D Ltd | Real estate | 2023 |
| JI People Advisory Ltd | Administrative & support | 2025 |
| Jianware Limited | Information & communication | 2022 |
| Jibees Limited | Health & social care | 2013 |
| Jill Duke Limited | Professional & scientific | 1986 |
| JIM Preen Media Limited | Professional & scientific | 2021 |
| JIM Sessions Ltd | Information & communication | 2025 |
| JIM Sinclair Limited | Professional & scientific | 2004 |
| Jimmy Greaves Academy Ltd | Education | 2018 |
| Jives Investment Ltd | Hospitality | 2025 |
| JJ Customs Ltd | Wholesale & retail | 2021 |
| JJ Services AC11 YOU Ltd | Construction | 2025 |
| Jjba Ltd | Construction | 2023 |
| Jjvi Limited | Real estate | 2024 |
| JK Autotech Ltd | Professional & scientific | 2025 |
| JKG Electrical Ltd | Construction | 2017 |
| JLC Mechanical Ltd | Wholesale & retail | 2025 |
| JLE Property Services Ltd | Construction | 2025 |
| JLI PMO Ltd | Administrative & support | 2025 |
| JLK Developments Ltd | Construction | 2025 |
| JM Anderson Limited | Administrative & support | 2009 |
| JN Swanage Ltd | Real estate | 2016 |
| JO Fletcher Books Limited | Information & communication | 2011 |
| JO Reeves Coaching Limited | Professional & scientific | 2024 |
| JO Smart Limited | Wholesale & retail | 2011 |
| JOE Bridger Electrical Contractor Ltd | Construction | 2023 |
| John Hatchard Limited | Professional & scientific | 2016 |
| John Rockliffe Limited | Education | 2003 |
| Johnsons (Leigh) Limited | Real estate | 1963 |
| Joinery and Interiors Ltd | Manufacturing | 2017 |
| JON Berry Coordination Ltd | Construction | 2022 |
| JON Scott Limited | Construction | 2007 |