| Icecourt Properties Limited | Real estate | 1993 |
| Icecourt Properties Reversions Limited | Real estate | 2024 |
| Ieyan BOA Limited | Wholesale & retail | 2021 |
| Ihe-Uk Ltd | Other services | 2009 |
| Ikies Publishing Ltd | Information & communication | 2025 |
| Iktrix Limited | Information & communication | 2002 |
| IL SIM Training Ltd | Transport & logistics | 2026 |
| Imperial Diagnostix Laboratories Ltd | Wholesale & retail | 2022 |
| Inca Creative Print Limited | Manufacturing | 2003 |
| Indetrac Limited | Manufacturing | 2014 |
| Indie Insight Ltd | Professional & scientific | 2016 |
| Inessence Beauty Salon Ltd | Other services | 2025 |
| Information Environments Limited | Professional & scientific | 1990 |
| Ingeneering Limited | Information & communication | 1987 |
| Inkpen Associates Limited | Information & communication | 1994 |
| Inside Aluminium (Stylmark UK & Europe) Limited | Wholesale & retail | 2010 |
| Instone Air Line Limited | Transport & logistics | 1996 |
| Instone Air Services Limited | Transport & logistics | 1977 |
| Interlinga Limited | Information & communication | 2025 |
| International Animal Airtransport Limited | Administrative & support | 2019 |
| International Mountain Biking Association (UK) | Other services | 2008 |
| Intodogs Ltd | Other services | 2024 |
| Intrex Properties Limited | Real estate | 1987 |
| Intrinsic Healthcare Limited | Health & social care | 2025 |
| Intyre Solutions Limited | Information & communication | 2015 |
| Inzy Limited | Information & communication | 2017 |
| IPT Contracting Services Ltd | Information & communication | 2016 |
| Ironstone Audio Limited | Information & communication | 2014 |
| Iscertus Limited | Information & communication | 2016 |
| Island Health Concierge Limited | Health & social care | 2024 |
| J & K Asset Management Limited | Real estate | 2004 |
| J & K Design Projects Limited | Construction | 2004 |
| J Farrer Plumbing & Heating Ltd | Construction | 2026 |
| J K Bridge & Co Limited | Information & communication | 2010 |
| J Swabey Driver Hire Ltd | Transport & logistics | 2018 |
| J&K Development Projects Limited | Construction | 2022 |
| J&K Freehold Management Ltd | Real estate | 2019 |
| J. E. B. Thatcher Reversions Limited | Real estate | 2024 |
| J. Roberts & SON (Gunmakers) Limited | Manufacturing | 1967 |
| J.D.T. Finance & Leasing Limited | Administrative & support | 1980 |
| J.H.P. Consultancy Ltd | Financial services | 2019 |
| Jackie Van Bueren Communications Limited | Information & communication | 2024 |
| Jacobs Bagels Worthing Limited | Hospitality | 2025 |
| Jaloma Developments Limited | Construction | 2025 |
| Jaloma Land Limited | Construction | 2025 |
| Jaloma Sky Limited | Construction | 2025 |
| Jasper Real Estate Group Limited | Financial services | 2025 |
| JAY JO Smith Limited | Real estate | 2025 |
| Jayne Withinshaw Limited | Health & social care | 2017 |
| Jays Pool Maintenance Limited | Water & waste | 2018 |
| Jaysee Contracting Ltd | Professional & scientific | 2025 |
| Jayswood (West Chiltington) Management Company Ltd | Households | 2013 |
| JCW Business Solutions Limited | Professional & scientific | 2020 |
| JD Training & Development Ltd | Professional & scientific | 2007 |
| JDS Mattos Consulting Ltd. | Information & communication | 2016 |
| Jefferies Farm Trade Centre Limited | Extraterritorial | 2019 |
| Jericho Prize for Children's Writing CIC | Administrative & support | 2023 |
| Jetcheck Services Ltd | Transport & logistics | 2023 |
| Jgrice Electrical Ltd | Construction | 2024 |
| Jhgpco Limited | Construction | 2016 |
| JJ Gardening Limited | Administrative & support | 2003 |
| JK Physiotherapy Limited | Health & social care | 2010 |
| JLD Branding Ltd | Professional & scientific | 2019 |
| Jlls Music Limited | Arts & recreation | 2025 |
| JM Brickwork Ltd | Construction | 2010 |
| JMT Auto Ltd | Wholesale & retail | 2026 |
| Joanna Hayden Architects Ltd | Professional & scientific | 2021 |
| Joanna's Boutique Tearoom (Chichester) Limited | Hospitality | 2022 |
| Joanna's Boutique Tearoom (Cranleigh) Limited | Hospitality | 2024 |
| Joanna's Boutique Tearoom Ltd | Hospitality | 2015 |
| John Howie & Associates Ltd. | Administrative & support | 2019 |
| John Sleight Graphics Ltd | Professional & scientific | 2012 |
| John's Cross (Holdings) Limited | Real estate | 1972 |
| Johns' Yard 2 Limited | Real estate | 2021 |
| JON Scholefield Ltd | Professional & scientific | 2020 |
| JP Accountancy Services (Sussex) Limited | Professional & scientific | 2021 |
| JP Trent Ltd | Professional & scientific | 2024 |
| JPM Capital Ltd | Financial services | 2020 |
| JR Trident Properties Ltd | Real estate | 2020 |
| Jspk Consulting Ltd | Professional & scientific | 2025 |
| JT Builds and Specialised Carpentry Ltd | Construction | 2019 |
| JTA Investments Limited | Real estate | 2025 |
| Jubel Living Limited | Wholesale & retail | 2020 |
| Jubel Trading Limited | Wholesale & retail | 2021 |
| Judd Limited | Manufacturing | 2008 |
| Julian Brown Associates Limited | Professional & scientific | 2025 |
| Juno Digico Ltd | Information & communication | 2025 |
| Jurisatlas Publishing Limited | Real estate | 2026 |
| JVM Group Holdings Limited | Financial services | 2020 |
| K & D Construction Sussex Ltd | Construction | 2025 |
| K Crumley Construction Ltd | Construction | 2015 |
| K7R Ltd | Financial services | 2023 |
| Kaeru Property Ltd | Real estate | 2024 |
| Kaeru Wealth Management Ltd | Financial services | 2024 |
| Kawauso Ltd | Professional & scientific | 2021 |
| Kearney Point Resources Ltd | Professional & scientific | 2021 |
| Kenstaff Holdings Ltd | Professional & scientific | 2016 |
| Kerry Whistles Limited | Manufacturing | 1997 |
| Kerslake Medical Ltd | Health & social care | 2016 |
| Keystone Projects & Management Limited | Financial services | 2000 |