| J Holt Plumbing Ltd | Construction | 2026 |
| J Mccartney Plastering Ltd | Construction | 2012 |
| J Morris and SON Consultancy Ltd | Other services | 2015 |
| J R Saunders Ltd. | Construction | 2014 |
| J&J Fuels Ltd | Wholesale & retail | 2025 |
| J&Z Auto Repairs Limited | Wholesale & retail | 2018 |
| J. B. Tuning Limited | Administrative & support | 2009 |
| J.E. Chauffeur Services (One) Limited | Transport & logistics | 2001 |
| J.Fisher Contracting Ltd | Financial services | 2025 |
| J.R.S & SON Limited | Construction | 2018 |
| Jabelle Management Ltd | Financial services | 2014 |
| Jace Homes Ltd | Professional & scientific | 2024 |
| Jack Nicholls Golf Ltd | Wholesale & retail | 2024 |
| Jack Russell Terrier Rescue UK CIC | Agriculture & fishing | 2017 |
| Jacob Phillips Drainage & Plumbing Ltd | Water & waste | 2026 |
| Jade Jefford Permanent Cosmetics Ltd | Other services | 2017 |
| JAF Electrical Ltd | Construction | 2019 |
| Jagara Canopies Limited | Wholesale & retail | 2019 |
| Jagbada Enterprises Limited | Health & social care | 2024 |
| Jalite Public Limited Company | Administrative & support | 1983 |
| James Holmes Bespoke Furniture Limited | Manufacturing | 2025 |
| James Oglethorpe PRE School Ltd | Education | 2017 |
| Jamtek Ltd | Information & communication | 2024 |
| Jamye Limited | Other services | 2023 |
| JAP Auto Spares Ltd | Wholesale & retail | 2014 |
| Jarrod Ltd | Other services | 2013 |
| Jatakmlt Ltd | Health & social care | 2015 |
| Jaybee Trading Ltd | Wholesale & retail | 2023 |
| JB Addo Limited | Real estate | 2024 |
| JB Elite Limited | Construction | 2025 |
| JB Media Limited | Information & communication | 2026 |
| JBD Solutions Limited | Professional & scientific | 2017 |
| Jcap Properties Ltd | Other services | 2024 |
| JCS Group Services Limited | Construction | 2015 |
| JDA Maintenance Group Limited | Construction | 2022 |
| JDG Data Limited | Professional & scientific | 2019 |
| JDW Productions Ltd | Information & communication | 2026 |
| Jdwatkins Limited | Construction | 2025 |
| Jebodys Limited | Administrative & support | 2014 |
| Jenkinson Lord Limited | Wholesale & retail | 2000 |
| Jennings Future Solutions Ltd | Hospitality | 2024 |
| Jepc Property Services Limited | Real estate | 2025 |
| Jeremy Place Limited | Information & communication | 1997 |
| JF Video Ltd | Information & communication | 2024 |
| Jfjl Haulage Limited | Transport & logistics | 2025 |
| JFR Barnard Limited | Construction | 2017 |
| JH Carpentry and Locks Limited | Manufacturing | 2019 |
| JH Events Management Ltd | Administrative & support | 2026 |
| JJB Joinery & Locksmiths Ltd | Construction | 2024 |
| Jjwhite Properties Ltd | Real estate | 2021 |
| JK Hawkins Ltd | Information & communication | 2024 |
| JK Services (South East) Limited | Professional & scientific | 2017 |
| JKT Supplies Ltd | Wholesale & retail | 2024 |
| JLA Carpentry and Building Services Ltd | Construction | 2011 |
| JMA Asset Management Ltd | Real estate | 2024 |
| JMA Commercial Surveyors Ltd | Professional & scientific | 2022 |
| JMA Properties Limited | Real estate | 2002 |
| JMB Capital ME Limited | Professional & scientific | 2024 |
| JMB Land and Development Limited | Construction | 2021 |
| JMB Partners (UK) LLP | | 2024 |
| JMB Real Estate Partners LLP | | 2024 |
| JMP Cleaning Services Limited | Administrative & support | 2010 |
| JMP PPM Consultancy Ltd | Professional & scientific | 2024 |
| JMP VA Limited | Administrative & support | 2025 |
| Joanne House Property Limited | Households | 2022 |
| John Hills Residential Lettings & Property Management Limited | Real estate | 2013 |
| John Rowlinson Consulting Ltd | Information & communication | 2021 |
| Jones Mather Limited | Real estate | 2010 |
| Jowers Carpentry & More Limited | Construction | 2025 |
| JPF CAD & BIM Solutions Limited | Administrative & support | 2015 |
| JPT Limited | Professional & scientific | 2017 |
| JRL Property Development Limited | Construction | 2025 |
| JRM Builders Essex Ltd | Construction | 2022 |
| JRP Classics Limited | Wholesale & retail | 2011 |
| Jsjk Properties Limited | Real estate | 2022 |
| JSJZ2020 Ltd | Hospitality | 2021 |
| JT Carpentry Limited | Construction | 2022 |
| JTL Interiors Ltd | Construction | 2021 |
| Judge Medical Services Ltd | Health & social care | 2022 |
| Judna Limited | Professional & scientific | 2024 |
| Juliet Heap Ltd. | Professional & scientific | 2012 |
| Just Curls Ltd | Other services | 2022 |
| Just DO FAB Limited | Other services | 2022 |
| JV Founders Limited | Administrative & support | 2025 |
| JW Loft & Sons Ltd | Construction | 2022 |
| K & R Utilities Limited | Construction | 2023 |
| K a Naturals Ltd | Wholesale & retail | 2022 |
| K Glover Limited | Professional & scientific | 2014 |
| K L C Developments Limited | Real estate | 2011 |
| K Lacey Construction Ltd | Construction | 2020 |
| K.C Fibre and Data Solutions Ltd | Construction | 2025 |
| K.C.P. Demolition & Developments Limited | Construction | 2024 |
| K2L Designs Ltd | Professional & scientific | 2019 |
| KAJ RAY Carpentry Limited | Construction | 2017 |
| Kamaro Trans Ltd | Transport & logistics | 2022 |
| Kare Properties Essex Limited | Real estate | 2021 |
| KARRM7 Ltd | Financial services | 2023 |
| Kate Mclaren Design Limited | Administrative & support | 2009 |
| Kayani MED Ltd | Health & social care | 2024 |
| Kcim Consultancy Limited | Information & communication | 2026 |