| Izenq Limited | Information & communication | 2025 |
| J & M Property Contractors Limited | Construction | 2026 |
| J B Building Essex Ltd | Construction | 2019 |
| J B Carpet and Oven Cleaning Ltd | Administrative & support | 2025 |
| J Byford & Co Limited | Professional & scientific | 2018 |
| J Byford Holdings Limited | Financial services | 2018 |
| J Castle Legacy Ltd | Professional & scientific | 2019 |
| J D Mcdavitt Accountants Ltd | Professional & scientific | 2007 |
| J D Mcdavitt Properties Ltd | Real estate | 2023 |
| J Laidlaw Services Ltd | Professional & scientific | 2012 |
| J M L Productions Ltd | Construction | 2019 |
| J M Upholstery Limited | Other services | 2011 |
| J Palmer Events Ltd | Arts & recreation | 2019 |
| J S L Property Services Limited | Construction | 2004 |
| J T Contractors & Sons Ltd | Construction | 2026 |
| J Tech Jewellery Limited | Manufacturing | 2016 |
| J&J Recruitment Solutions Ltd | Administrative & support | 2012 |
| J&L Mortgage Solutions Ltd | Professional & scientific | 2015 |
| J. Fuller and Sons Limited | Manufacturing | 1947 |
| J. R. Tyson & Sons Limited | Manufacturing | 1973 |
| J.A.M. Limited | Manufacturing | 1982 |
| J.F.W.S. Limited | Other services | 1999 |
| J.P. Reis (UK) Limited | Information & communication | 2007 |
| J.R. Tyson (Powder Coating) Limited | Professional & scientific | 1982 |
| J.Sloan Limited | Other services | 2025 |
| Jack Carter Architects Ltd | Professional & scientific | 2017 |
| Jack Contracts Ltd | Construction | 2019 |
| Jackson Pettitt Contracting Solutions Limited | Construction | 2012 |
| Jackson Pettitt Limited | Construction | 1996 |
| Jackson Wharf RTM Company Limited | Households | 2023 |
| Jadecrest Consulting Ltd | Professional & scientific | 2025 |
| Jagzinspired Ltd | Wholesale & retail | 2024 |
| Jake Halsey Football Ltd | Arts & recreation | 2022 |
| JAM Factory Freehold Limited | Households | 2009 |
| James Wyllie Limited | Financial services | 2006 |
| Jameswebbmep Ltd | Construction | 2025 |
| Jamie's Nutrition Limited | Health & social care | 2021 |
| Jarvis Blake & Glenwright (E14) Ltd | Construction | 2014 |
| JAS Building and Groundworks Ltd | Construction | 2014 |
| JAW Housing Ltd | Real estate | 2024 |
| Jayel (Warwick) Limited | Administrative & support | 2006 |
| Jbbstore Ltd | Wholesale & retail | 2022 |
| Jbdg Property Ltd | Real estate | 2023 |
| JC Growth Partner Ltd | Professional & scientific | 2023 |
| JC Thomas Properties Limited | Real estate | 2018 |
| JCO Landscaping and Maintenance Ltd | Administrative & support | 2017 |
| JDA Carpentry & Building Ltd | Manufacturing | 2025 |
| JE Medics Limited | Health & social care | 2016 |
| Jeakins Motor Limited | Wholesale & retail | 1988 |
| Jeanne Robertson Limited | Administrative & support | 2015 |
| Jeff Hammond Accounting Limited | Professional & scientific | 2010 |
| Jeffrey Read Limited | Real estate | 2017 |
| Jentel Packing Ltd | Transport & logistics | 2014 |
| Jept Holdings Ltd | Real estate | 2026 |
| JHG1 Limited | Construction | 2016 |
| JHH Pest Control Ltd | Administrative & support | 2025 |
| Jive Artist Events Agency Ltd | Administrative & support | 2024 |
| JJ Barnes Carpentry Ltd | Construction | 2021 |
| JJ Contracts Ltd | Construction | 2019 |
| Jjit Consulting Limited | Information & communication | 2012 |
| JK Auto Body Repairs Ltd | Wholesale & retail | 2018 |
| Jlde Enterprises Limited | Information & communication | 2011 |
| JMP Plastering and Rendering Limited | Construction | 2016 |
| Joester Wellbeing Ltd | Other services | 2024 |
| Joey Essex Management Ltd | Arts & recreation | 2011 |
| JOH Property Management Ltd | Real estate | 2024 |
| Johnson School of Motoring Limited | Education | 2007 |
| Jolly Hucksters Ltd | Hospitality | 2022 |
| Jones Bespoke Games Tables Ltd | Wholesale & retail | 2025 |
| Joseph & Rudyard Court RTM Company Limited | Households | 2022 |
| JP Build Limited | Construction | 2018 |
| JP Legal Assist Limited | Professional & scientific | 2020 |
| JPR & Sons Electrical Services Ltd | Construction | 2016 |
| JPS Howard & Sons Ltd | Transport & logistics | 2012 |
| JR Builders & Developers Limited | Construction | 2017 |
| JR Print Studio Ltd | Wholesale & retail | 2025 |
| JRH Civil Engineering Ltd | Construction | 2010 |
| JSC Contracting Ltd | Construction | 2021 |
| JSD UK Trade Ltd | Wholesale & retail | 2024 |
| JSS Estates Ltd | Real estate | 2018 |
| Juniper Housing Ltd | Real estate | 2024 |
| JUNZA2025 Ltd | Hospitality | 2024 |
| Just the Present Ltd | Wholesale & retail | 2021 |
| JW Bespoke Jewellers Ltd | Professional & scientific | 2023 |
| Jwg-It Limited | Professional & scientific | 2006 |
| K & D Holdings (Sussex) Limited | Financial services | 2024 |
| K Kooling Ltd | Construction | 2019 |
| K N Medics Limited | Health & social care | 2012 |
| K P Performance Cars Limited | Wholesale & retail | 2022 |
| K8 Electrical Ltd | Construction | 2021 |
| K9 Associates Ltd | Administrative & support | 2017 |
| Kajaro Limited | Information & communication | 2009 |
| Kaledou Properties Limited | Real estate | 2023 |
| Kandy Accounting Services Ltd | Professional & scientific | 2020 |
| Kangei Judo Club CIC | Education | 2026 |
| Kansagra Optometry Limited | Health & social care | 2004 |
| KAR Motor Company Essex Ltd | Wholesale & retail | 2024 |
| Kasinara Limited | Real estate | 2020 |
| Kbam Holding Ltd | Administrative & support | 2026 |
| KD Technology Services Ltd | Information & communication | 2019 |