| I’M Jorge Complete Home & Carpentry Solutions Ltd | Construction | 2026 |
| J & D Rentals Ltd | Real estate | 2023 |
| J & H Essex Construction Ltd | Construction | 2025 |
| J & N Holding Partnership LLP | | 2026 |
| J & O Meats Ltd | Wholesale & retail | 2018 |
| J & S Mastics Limited | Construction | 1994 |
| J a B Building Services Ltd | Construction | 2015 |
| J a Carr Engineering Ltd | Construction | 2016 |
| J GOW Consulting Limited | Information & communication | 2020 |
| J H Bathrooms Limited | Construction | 2013 |
| J J Twinn Consulting Ltd | Transport & logistics | 2013 |
| J L Page Property Ltd | Households | 2020 |
| J M (Essex) Ltd | Extraterritorial | 2017 |
| J M L Arts Limited | Professional & scientific | 2003 |
| J Morgan & Sons Limited | Construction | 2023 |
| J Morton Services Limited | Other services | 2018 |
| J Neville Interiors Ltd | Construction | 2007 |
| J Nichols Supplies Ltd | Wholesale & retail | 2010 |
| J Patrick Photography Ltd | Professional & scientific | 2019 |
| J R Utilities Ltd | Administrative & support | 2013 |
| J Spec Roofing Technologies Limited | Construction | 2017 |
| J V Electrical Ltd | Construction | 2007 |
| J Willson (Signs) Limited | Other services | 2008 |
| J&Co Architects Ltd | Professional & scientific | 2025 |
| J&G Hair Limited | Other services | 2024 |
| J. C. Distribution Limited | Wholesale & retail | 1998 |
| J. Collins Brickwork & Building Services Ltd | Construction | 2025 |
| J. E. Strutt Farming Limited | Other services | 1978 |
| J. Reid (Essex) Limited | Construction | 2015 |
| J.D. Wyatt Cornwall Limited | Construction | 2018 |
| J.D. Wyatt Limited | Construction | 2003 |
| J.D.M. Scaffolding Limited | Construction | 1998 |
| J.E. Strutt (London) Limited | Other services | 1979 |
| J.E.D. Investments Limited | Real estate | 2004 |
| J.E.G Construction Ltd | Construction | 2026 |
| J.E.Strutt Limited | Other services | 1957 |
| J.J.Sullivan & SON Building Contractors Limited | Construction | 2001 |
| J.P. Film Services Ltd | Information & communication | 2016 |
| J@Ottexpress Ltd | Transport & logistics | 2023 |
| JA Advanced Tech Ltd | Information & communication | 2022 |
| JA Music Ltd | Education | 2019 |
| Jack & Drury Accountants Limited | Professional & scientific | 2023 |
| Jack Holdings Limited | Financial services | 2023 |
| Jack Thomas Building Services Ltd | Construction | 2020 |
| Jack William Roofing Ltd | Construction | 2022 |
| Jack Woollcott Properties Limited | Real estate | 2020 |
| Jackrose Holdings Limited | Real estate | 2026 |
| Jackrose Investments Limited | Professional & scientific | 2020 |
| Jackson (Plant Hire) Limited | Construction | 1958 |
| Jackson Thorn Properties Limited | Financial services | 2020 |
| Jacobs & Leigh Limited | Wholesale & retail | 2016 |
| Jade Jefford Laser Tattoo Removal Ltd | Other services | 2024 |
| Jade Tiger Limited | Hospitality | 2026 |
| Jaflong Limited | Hospitality | 2016 |
| Jago Graphics Limited | Administrative & support | 2021 |
| Jake Price Limited | Financial services | 2024 |
| Jalg Consultancy Limited | Information & communication | 2012 |
| Jalken Consulting Ltd | Professional & scientific | 2018 |
| Jaloti Ltd | Real estate | 2025 |
| JAM Builders Ltd | Construction | 2018 |
| JAM Media Research Ltd | Education | 2017 |
| Jamack Limited | Other services | 1997 |
| James and LEE Ltd | Construction | 2020 |
| James Bonner Ltd | Other services | 2018 |
| James Furzer Designs Limited | Professional & scientific | 2020 |
| James Grantham Estates Ltd | Real estate | 2024 |
| James Young & Associates Limited | Financial services | 2013 |
| Jamesac Surveys Ltd | Administrative & support | 2016 |
| Jane Nicholson Consulting Limited | Administrative & support | 2020 |
| Jarpay Limited | Financial services | 2017 |
| Jaseword Limited | Hospitality | 2018 |
| Jashikan Limited | Real estate | 2026 |
| Jason Gardner Fitness Limited | Arts & recreation | 2021 |
| Jaspergate Ltd | Real estate | 2021 |
| Jaydee Powersports Limited | Other services | 2018 |
| JB Developments (SE) Ltd | Real estate | 2024 |
| JB Domestic Repairs Limited | Other services | 2026 |
| JBD Property Ltd | Real estate | 2020 |
| JBR Electrical Installations Ltd | Construction | 2023 |
| JC Sprinklers Limited | Construction | 2023 |
| JCM Building Solutions Ltd | Construction | 2019 |
| JCR Contracts London Ltd | Construction | 2023 |
| JDE Driver Hire Ltd | Transport & logistics | 2019 |
| JDL Group Ltd | Construction | 2021 |
| JDM Retail Consulting Limited | Professional & scientific | 2020 |
| JDT Tech Ltd | Construction | 2025 |
| JE Driving Ltd | Transport & logistics | 2024 |
| Jealous Beauty Rooms Limited | Other services | 2018 |
| JEH Advisory Limited | Financial services | 2024 |
| Jellie UK Limited | Information & communication | 2023 |
| JEN Brockwell Ltd | Professional & scientific | 2021 |
| Jenah Group Limited | Manufacturing | 2023 |
| Jennifer Challenger Coaching and Consulting Ltd | Professional & scientific | 2019 |
| Jennifer Gardiner Ltd | Professional & scientific | 2020 |
| Jeremy Hosken Limited | Professional & scientific | 2017 |
| JES Mortgages Ltd | Financial services | 2024 |
| Jessica L Betts Ltd | Professional & scientific | 2023 |
| Jessie Foakes Ltd | Arts & recreation | 2022 |
| Jetabroad (UK) Limited | Administrative & support | 2018 |
| Jewellery Design Centre Limited | Wholesale & retail | 2010 |