| International Express Co. Limited | Professional & scientific | 1997 |
| International Food Link Limited | Wholesale & retail | 1996 |
| Internet Assist Limited | Information & communication | 1996 |
| Internet Marketing Holdings Ltd | Information & communication | 2024 |
| Interwood Limited | Extraterritorial | 2002 |
| Intuition (AB) Ltd | Education | 2020 |
| Intuitive Design (UK) Limited | Professional & scientific | 2006 |
| Isohigh Limited | Transport & logistics | 1985 |
| ISU Development Limited | Real estate | 2023 |
| IT Juice Ltd | Information & communication | 2026 |
| Ivory Leisure Ltd | Real estate | 2006 |
| IVY Fields Rentals Ltd | Real estate | 2025 |
| Ivybuild Holdings Limited | Construction | 2010 |
| Ivybuild Limited | Construction | 1992 |
| IYA Moments Limited | Professional & scientific | 2025 |
| Izumi Properties Limited | Real estate | 2010 |
| Izumi Restaurant (Maldon) Limited | Hospitality | 2010 |
| J & B Motors Limited | Wholesale & retail | 2019 |
| J Barber Accountancy Limited | Professional & scientific | 2015 |
| J J Getaways Ltd | Real estate | 2025 |
| J P Property Consultancy Ltd | Real estate | 2018 |
| J R Scaffolding Suppliers Ltd | Construction | 2016 |
| J T Foiling Limited | Manufacturing | 2026 |
| J Thomas Recruitment Limited | Administrative & support | 2020 |
| J W Adams Homes Ltd | Construction | 2010 |
| J W J Booty Limited | Manufacturing | 2004 |
| J Welham Electrical Limited | Construction | 2026 |
| J&J Early Years Educators Ltd | Health & social care | 2018 |
| J&R Construction Services Ltd | Construction | 2019 |
| J. & M. Seabrook (Tollesbury) Limited | Agriculture & fishing | 1973 |
| J.Anderson & Sons Landscapes Limited | Construction | 2017 |
| J.G.Farrier Services Limited | Professional & scientific | 2015 |
| J.K. Holdings Limited | Construction | 1972 |
| J.M.I. Agricultural Contractors Limited | Agriculture & fishing | 2001 |
| J.R Media Consultants Ltd | Other services | 2008 |
| J.S.O Properties and Investments Limited | Real estate | 2025 |
| J.W.F. Construction Limited | Construction | 2017 |
| JA Bourner Limited | Professional & scientific | 2019 |
| JA Professional Services International Ltd | Professional & scientific | 2018 |
| Jackfrancis Media Limited | Professional & scientific | 2010 |
| Jackie & Co Kensington Limited | Other services | 2019 |
| Jackson & Co Property Services Limited | Real estate | 2007 |
| Jacs Electrical Services Ltd | Construction | 2021 |
| JAF Trading Limited | Administrative & support | 2019 |
| James Grant Services Ltd | Information & communication | 2019 |
| James Joseph Services Limited | Financial services | 2016 |
| James Medcraft Ltd | Professional & scientific | 2013 |
| Jaqui Rungay Ltd | Professional & scientific | 2024 |
| JAR Tools Limited | Wholesale & retail | 2017 |
| JB Beauty Ltd | Other services | 2016 |
| JB Commercial Vehicles Limited | Wholesale & retail | 2025 |
| Jbatts Ltd | Administrative & support | 2021 |
| JBC Protect Learning Limited | Education | 2021 |
| JBC Protect Security Services Limited | Administrative & support | 2013 |
| Jbecerra Limited | Other services | 2013 |
| JBJ Supplies Ltd | Wholesale & retail | 2024 |
| JBL Safety Services Limited | Administrative & support | 2024 |
| JC Site Solution Limited | Administrative & support | 2025 |
| JCK Search Limited | Administrative & support | 2021 |
| JDB Installs Ltd | Construction | 2023 |
| JDK Services Ltd | Manufacturing | 2015 |
| Jeff Paws Limited | Professional & scientific | 2026 |
| Jess W Properties Ltd | Real estate | 2026 |
| Jessex Property Ltd | Real estate | 2017 |
| JFL Haulage Ltd | Transport & logistics | 2023 |
| JG & MG Property Ltd | Real estate | 2023 |
| JGC Data Solutions Limited | Information & communication | 2024 |
| JGH Enterprises Limited | Professional & scientific | 2026 |
| Jheelan Associates Network Limited | Health & social care | 2007 |
| Jiangsu Black Stone Limited | Administrative & support | 2024 |
| Jillco Limited | Professional & scientific | 2014 |
| Jingle Communications Ltd | Professional & scientific | 2012 |
| JJ Gardens & Grounds Ltd | Administrative & support | 2025 |
| JJ Ironing and Cleaning Limited | Administrative & support | 2010 |
| JJB Survey and Property Services Ltd | Real estate | 2023 |
| JK (East) Holdings Limited | Real estate | 2013 |
| JKN Installations Ltd | Wholesale & retail | 2022 |
| Jl-Eq Ltd | Wholesale & retail | 2025 |
| JLM Holdingco Limited | Financial services | 2026 |
| JLM Investco Limited | Construction | 2026 |
| JLP Hospitality Management Ltd | Hospitality | 2019 |
| JMD Support Consultancy Ltd | Information & communication | 2023 |
| JMX Detailing Ltd | Wholesale & retail | 2025 |
| Jobstocks Limited | Real estate | 1958 |
| Jodari Limited | Manufacturing | 2004 |
| Jogangroup Ltd | Professional & scientific | 2026 |
| John Graves Direct Limited | Real estate | 1997 |
| Johnson & Associates Recruitment Specialists Ltd | Administrative & support | 2015 |
| JON Knights Materials Consulting Limited | Professional & scientific | 2012 |
| Jones Projects Limited | Construction | 2004 |
| Jonet Fil-Store Ltd | Wholesale & retail | 2023 |
| Jordan Industrial Services Limited | Construction | 1997 |
| Joseph's Tree Solutions Limited | Administrative & support | 2024 |
| Joyeux Maldon Limited | Wholesale & retail | 2023 |
| Jpbrickworkandbuilding Ltd | Construction | 2020 |
| Jprn Ltd | Health & social care | 2016 |
| Jp’S Kitchen Limited | Hospitality | 2020 |
| JR Dogtrainer Limited | Other services | 2026 |
| JR Plant Repair Ltd | Manufacturing | 2024 |
| JR Property and Building Ltd | Real estate | 2021 |