| J I Turner Electrical Limited | Construction | 2019 |
| J J Flooring Services Limited | Construction | 2012 |
| J KAY Holdings Ltd | Real estate | 2021 |
| J L & D Hammond Holdings Limited | Financial services | 2023 |
| J L Soman Ltd | Hospitality | 2020 |
| J M Media World Ltd | Professional & scientific | 2022 |
| J Maslen Electrical Services Ltd | Construction | 2021 |
| J Mcgrane Limited | Hospitality | 2003 |
| J P M Contracting Limited | Professional & scientific | 2018 |
| J R Farming LLP | | 2013 |
| J R Lloyd Ltd | Arts & recreation | 2012 |
| J R Partridge Ltd | Real estate | 2014 |
| J R Rayner Builders Limited | Construction | 2008 |
| J Rivers Utilities Limited | Energy | 2017 |
| J S 5 Limited | Real estate | 1998 |
| J S Aggregates Limited | Transport & logistics | 2025 |
| J S Lazell Limited | Wholesale & retail | 2026 |
| J S Tech Consultancy Limited | Information & communication | 2018 |
| J Stephens Group Limited | Construction | 2025 |
| J Wilson Plumbing & Heating Limited | Construction | 2008 |
| J&B Resurfacing Ltd | Professional & scientific | 2023 |
| J&C Cosworth Solutions Limited | Construction | 2025 |
| J&C's Party Pets Limited | Agriculture & fishing | 2015 |
| J&D Property Trading Limited | Real estate | 2017 |
| J&J Commercial Haulage Ltd | Transport & logistics | 2020 |
| J&J DIL Ltd | Manufacturing | 2018 |
| J&J Young Ltd | Real estate | 2022 |
| J&L Hand Car Wash Ltd | Wholesale & retail | 2022 |
| J&L Massage Limited | Health & social care | 2026 |
| J&M Diagnostics Ltd | Wholesale & retail | 2024 |
| J&S Properties Management Ltd | Real estate | 2023 |
| J. a. Fairweather Associates. | | 2000 |
| J. Gard & Sons Limited | Wholesale & retail | 1949 |
| J. S. Trucks (Essex) Limited | Wholesale & retail | 2019 |
| J. W. Lodge & Sons Limited | Transport & logistics | 1973 |
| J.A.Sargeant Ltd | Financial services | 2023 |
| J.A.Shadbolt Ltd | Manufacturing | 2014 |
| J.D.W. Ltd. | Construction | 1997 |
| J.E Property Lets Ltd | Real estate | 2021 |
| J.E.M. Building Designs Ltd. | Construction | 2011 |
| J.F. Young & Sons Ltd | Construction | 2004 |
| J.H Hub Ltd | Professional & scientific | 2020 |
| J.H. Trading Hub Limited | Wholesale & retail | 2014 |
| J.J Freight & Logistics Limited | Transport & logistics | 2022 |
| J.J.Bernardes & SON Limited | Construction | 1944 |
| J.L.& D.Hammond(Hammonds)Limited | Wholesale & retail | 1955 |
| J.M Scaffolding London Ltd | Construction | 2018 |
| J.Mills Property Investments Limited | Construction | 2024 |
| J.R.B. Electrical Testing Services Ltd | Manufacturing | 2005 |
| J.S. Wright and Sons Limited | Manufacturing | 1956 |
| J.S.Horrey Property Ltd | Real estate | 2020 |
| J.T. Maverick Limited | Financial services | 2017 |
| J.W. Gard (Builders) Limited | Professional & scientific | 1949 |
| J.W. Steele & Sons Group Limited | Financial services | 2020 |
| J.W. Steele & Sons Trustee Limited | Professional & scientific | 2020 |
| J.W.Steele & Sons Limited | Construction | 2005 |
| J.Woodcock Plumbing and Heating Limited | Construction | 2025 |
| JA Development Management Limited | Professional & scientific | 2025 |
| JA Richer Limited | Construction | 1998 |
| Ja:As Aesthetics Ltd | Other services | 2025 |
| Jaac India Ltd | Wholesale & retail | 2024 |
| Jacalu Limited | Real estate | 2019 |
| Jacc Property Ltd | Real estate | 2023 |
| Jack Arnold Facades & Drylining Ltd | Construction | 2021 |
| Jacked Gymnastics Limited | Arts & recreation | 2016 |
| Jackel Properties Limited | Real estate | 2018 |
| Jackson Construction Ltd | Construction | 2026 |
| Jacob Jepps Ltd | Professional & scientific | 2023 |
| Jadc Studio Ltd | Extraterritorial | 2023 |
| Jade-Euro-Med Limited | Manufacturing | 1998 |
| Jadscom Ltd | Information & communication | 2022 |
| Jaggard and Moore Ltd | Wholesale & retail | 2021 |
| Jagged Edge (Essex) Ltd | Other services | 2003 |
| Jaiks Limited | Construction | 2018 |
| Jake White Photos Limited | Professional & scientific | 2025 |
| Jakubowski Creative Developments Ltd | Construction | 2022 |
| Jala Holdings Limited | Financial services | 2022 |
| Jall FS Ltd | Financial services | 2024 |
| Jalu Habitats Ltd | Wholesale & retail | 2025 |
| JAM Ventures Ltd | Manufacturing | 2026 |
| Jamarda Limited | Real estate | 2010 |
| James Allan Promotions Limited | Arts & recreation | 2016 |
| James Barr & SON (Engineering) Limited | Agriculture & fishing | 1952 |
| James Beagle Design Ltd | Other services | 2026 |
| James Charles Group Ltd | Financial services | 2026 |
| James Dace Pianos Limited | Other services | 1999 |
| James Estates Co. Limited | Real estate | 2003 |
| James Foster Associates Limited | Administrative & support | 2020 |
| James Halls Garden Design Limited | Professional & scientific | 2012 |
| James Joseph (Estate Planning) Limited | Administrative & support | 2022 |
| James Joseph (Property Developments) Limited | Real estate | 2022 |
| James LEE Community Pubs Limited | Hospitality | 2025 |
| James Martin Interiors Ltd | Wholesale & retail | 2021 |
| James Rowe Projects Ltd | Construction | 2020 |
| James Sandrini Ltd | Professional & scientific | 2022 |
| James Sinclair Enterprises Ltd | Professional & scientific | 2018 |
| James Steele & Company Limited | Financial services | 2012 |
| James Stewart (Holdings) Limited | Financial services | 2020 |
| James Stewart Investments (Holdings) Limited | Financial services | 2020 |
| James Stewart Investments Ltd | Real estate | 2016 |