| J.A.H. Holdings Ltd | Financial services | 2016 |
| J.A.P.S. Developments Ltd | Construction | 2025 |
| J.A.P.S. Residentials Ltd | Real estate | 2025 |
| J.C. Vents Limited | Extraterritorial | 1979 |
| J.D.E. Plumbing & Heating Ltd | Construction | 2014 |
| J.H.S. Tree Care Ltd | Administrative & support | 2024 |
| J.L. Buttle Holdings Limited | Real estate | 1976 |
| J.Mcgrath Painting and Decorating Ltd | Construction | 2026 |
| J.R. Cross Limited | Real estate | 1958 |
| J.R.G. Contractors Limited | Construction | 2010 |
| J.S.R Construction Services Limited | Construction | 2023 |
| JA Automotive Developments Ltd | Wholesale & retail | 2020 |
| JA Cleaning Services Ltd | Administrative & support | 2026 |
| JAB Education Services Ltd | Education | 2013 |
| Jabinvesting Ltd | Real estate | 2025 |
| Jack of ALL Sports Limited | Education | 2025 |
| Jacquimitch Ltd | Health & social care | 2007 |
| Jadc.Properties. Ltd | Real estate | 2022 |
| Jade Palace 28 Ltd | Hospitality | 2026 |
| Jade Palace Ltd. | Hospitality | 1994 |
| Jade's Creations Ltd | Wholesale & retail | 2022 |
| Jakes Contracting Limited | Construction | 1997 |
| Jalsha Express Limited | Hospitality | 2015 |
| Jamang Estates Ltd | Real estate | 2025 |
| Jamang Properties Ltd | Real estate | 2025 |
| James & SON Limited | Construction | 1974 |
| James & SON Plasterers Holdings Limited | Financial services | 1978 |
| James Anang Limited | Health & social care | 2012 |
| James Court (SLH) Limited | Real estate | 2019 |
| James Debenham Limited | Information & communication | 2011 |
| James Govey & Company Ltd | Construction | 2019 |
| James Turvey Enterprises Ltd | Other services | 2018 |
| James Whiteley Ltd | Wholesale & retail | 2014 |
| Jamie M B Ltd | Real estate | 2024 |
| Jamies Fruit & VEG Ltd | Wholesale & retail | 2016 |
| Jason Bird Pipe Contracts Ltd | Construction | 2008 |
| Java Properties (Wickford) Ltd | Real estate | 2022 |
| Jayden JOE Limited | Information & communication | 2023 |
| Jazi Property Management Limited | Construction | 2025 |
| Jazolo Limited | Real estate | 1984 |
| JB Aesthetic Designs Ltd | Construction | 2025 |
| JB Domestics Essex Ltd | Other services | 2012 |
| JBH Electrics Ltd | Construction | 2024 |
| JD Accommodation Ltd | Households | 2024 |
| JD Door Security Ltd | Manufacturing | 2021 |
| JD Fire Alarms Limited | Administrative & support | 2018 |
| Jdeasnet Business Information Technology Services Ltd | Information & communication | 2015 |
| Jdeasnet Properties Ltd | Real estate | 2020 |
| JDG the Paving Experts Ltd | Construction | 2009 |
| JDH Plastering Limited | Construction | 2019 |
| JDN 2 Holdings Ltd | Financial services | 2026 |
| JE 28 (UK) Limited | Construction | 2015 |
| JE Consultancy Limited | Professional & scientific | 2013 |
| Jeakins Properties Limited | Real estate | 1993 |
| Jeani Property Ltd | Real estate | 2020 |
| JEH (HSE) Consultancy Limited | Administrative & support | 2013 |
| JEH Associates Ltd | Health & social care | 2023 |
| Jetsam Records Limited | Information & communication | 2023 |
| JF Creative Solutions Ltd | Information & communication | 2023 |
| JF Getaways Ltd | Real estate | 2025 |
| JF Production Services Limited | Arts & recreation | 2012 |
| JF Property Management Ltd | Real estate | 2023 |
| JF Property Partners Ltd | Real estate | 2011 |
| JG Motorsports Group Ltd | Wholesale & retail | 2019 |
| JHC & DC Butler Limited | Real estate | 2002 |
| Jiku Ltd | Wholesale & retail | 2024 |
| Jimicron Services Ltd | Construction | 2020 |
| JJ International Ltd | Wholesale & retail | 2026 |
| JJM Accountants (UK) Ltd | Professional & scientific | 2020 |
| JJM Property Lettings Ltd | Real estate | 2022 |
| Jjwh Limited | Financial services | 2023 |
| JK & JJ Enterprises Limited | Information & communication | 2024 |
| JK & TK Limited | Real estate | 2026 |
| JKR Lettings Limited | Real estate | 2020 |
| JL Ductwork Limited | Construction | 2022 |
| Jl-Media Ltd | Other services | 2006 |
| JLB Lighting Ltd | Construction | 2026 |
| JLC Motors Ltd | Wholesale & retail | 2020 |
| JLM Fire Ltd | Construction | 2025 |
| JLR Permanent Makeup Ltd | Water & waste | 2020 |
| JM Accounting Ltd | Professional & scientific | 2026 |
| JM Smartbuy Limited | Wholesale & retail | 2023 |
| Jmcg Business Services Limited | Transport & logistics | 2013 |
| JMP Automotive Limited | Wholesale & retail | 2020 |
| JMS Horseboxes Ltd | Manufacturing | 2021 |
| JMT Contracts (West END) Limited | Construction | 2004 |
| Jobey's Plumbing & Heating Services Ltd | Construction | 2026 |
| JOE Mclewin Strategy Ltd | Information & communication | 2025 |
| Joel Holding and Management Ltd | Real estate | 2025 |
| Joel Property Group Limited | Real estate | 2025 |
| John Hill Air Conditioning Limited | Construction | 2006 |
| John Holman & Sons Limited | Financial services | 2014 |
| John Holman Properties Limited | Agriculture & fishing | 2004 |
| John Martin Motors Limited | Wholesale & retail | 1963 |
| John Mcguinness Roofing Contractors Limited | Construction | 1997 |
| John Stevens Racing Ltd | Arts & recreation | 2023 |
| John Wyndham Hair Care Limited | Other services | 2003 |
| Johnson's of Essex Ltd | Wholesale & retail | 2017 |
| Jomax Engineering Limited | Construction | 2006 |
| Jomjens Ltd | Health & social care | 2018 |