| Icon Engineering Holdings Ltd | Financial services | 2018 |
| Icon Frames Limited | Construction | 2026 |
| Icreativity Limited | Information & communication | 2023 |
| Idress Mart Ltd | Wholesale & retail | 2026 |
| Ifeco Global Services Limited | Wholesale & retail | 2025 |
| IGC Enterprises (Cambs) Ltd | Wholesale & retail | 2019 |
| Iklb Consulting Ltd | Information & communication | 2025 |
| Ilashuk Limited | Other services | 2021 |
| IN Real Ltd | Construction | 2016 |
| Inagiffy Limited | Wholesale & retail | 2015 |
| Independent Private Anaesthetist Consultants LLP | | 2026 |
| Index European Corporation Ltd | Administrative & support | 2016 |
| Index Marketing Consortium Limited | Information & communication | 2005 |
| Indus Arts Festival Limited | Information & communication | 2025 |
| Infinatech Limited | Information & communication | 2019 |
| Infinique Ltd | Wholesale & retail | 2023 |
| Ingham Gardens Residents Association Limited | Households | 1996 |
| Innavisions Developments Ltd | Financial services | 2013 |
| Innavisions Limited | Extraterritorial | 1999 |
| Innergio Ltd | Professional & scientific | 2021 |
| Innovateandeat Limited | Hospitality | 2012 |
| Innovation Contracting Limited | Financial services | 2014 |
| Integrated Broadcast Solutions Limited | Professional & scientific | 2003 |
| Integrated Truck Services Ltd | Wholesale & retail | 2018 |
| Intrinsic Damp & Mould Solutions Ltd | Construction | 2026 |
| Introducer Advocate Limited | Other services | 2013 |
| Iris Falls Ltd | Wholesale & retail | 2023 |
| Ironstone Developments Limited | Construction | 2016 |
| Ironstone Property Limited | Real estate | 2015 |
| Irrelevant Entertainment Limited | Arts & recreation | 2025 |
| Isle Build Investments Limited | Real estate | 2004 |
| Itabacus Limited | Professional & scientific | 2001 |
| Italian Ranunculus UK Limited | Extraterritorial | 2025 |
| Ittley Ltd | Other services | 2025 |
| IVY Marketing Limited | Extraterritorial | 2020 |
| J & C Fencing Limited | Administrative & support | 2015 |
| J & J Marine Ltd | Manufacturing | 2024 |
| J & S Utility Services Ltd | Construction | 2020 |
| J Charlotte Landscapes Ltd | Administrative & support | 2024 |
| J Crowe Transport Limited | Transport & logistics | 2025 |
| J D H Leisure Ltd | Hospitality | 2013 |
| J England Construction Limited | Construction | 2015 |
| J England Holdings Ltd | Real estate | 2022 |
| J Gale Construction Ltd | Construction | 2023 |
| J H Cook Limited | Construction | 2004 |
| J H Gar-Dens Ltd | Construction | 2023 |
| J H Holdings & Investments Ltd | Financial services | 2023 |
| J J Sandberg Construction Limited | Construction | 2011 |
| J K Middleton Limited | Professional & scientific | 2014 |
| J Knight Design Ltd | Professional & scientific | 2022 |
| J Knight Group Ltd | Financial services | 2025 |
| J Knight Holdings Ltd | Real estate | 2025 |
| J L Williams Builders Ltd | Construction | 2010 |
| J Lockey Holdings Ltd | Wholesale & retail | 2021 |
| J M Ferrando Ltd | Administrative & support | 2014 |
| J P and SON Pearson Electrical Contractors Limited | Construction | 2023 |
| J R M Electrical (East) Limited | Construction | 2017 |
| J R Stott Limited | Wholesale & retail | 2003 |
| J S Holmes Leasing Limited | Administrative & support | 2024 |
| J Salisbury Limited | Real estate | 2020 |
| J W Brighty Ltd | Agriculture & fishing | 2012 |
| J&S Jetting Drainage Services Limited | Water & waste | 2015 |
| J. Rudd (ES) Limited | Agriculture & fishing | 2011 |
| J. W. Trayford Limited | Real estate | 1982 |
| J. Willis Kitchens & Bathrooms Ltd | Construction | 2022 |
| J.A. Mcmanus Plastering Ltd | Construction | 2022 |
| J.D Memorabilia Ltd | Wholesale & retail | 2023 |
| J.L Driving and Rigging Ltd | Transport & logistics | 2018 |
| J.M. Newling & SON Limited | Agriculture & fishing | 1978 |
| J.S. Holmes Automotive Limited | Wholesale & retail | 2023 |
| J.S. Motorcycles Ltd | Wholesale & retail | 2004 |
| JAB Essentials Ltd | Wholesale & retail | 2024 |
| Jade Finance (East Anglia) Limited | Administrative & support | 2018 |
| Jade Garden Food Ltd | Hospitality | 2025 |
| Jade Mortgages Limited | Financial services | 2023 |
| Jagatab&Sons.Uk Ltd | Wholesale & retail | 2016 |
| JAJ Commercial Limited | Wholesale & retail | 2024 |
| Jakew Consultancy Ltd | Professional & scientific | 2023 |
| Jakew Quality Software Ltd | Information & communication | 2024 |
| Jakubas Limited | Transport & logistics | 2016 |
| Jamco Properties Ltd | Manufacturing | 2017 |
| James Else Carpentry Limited | Construction | 2018 |
| James Fowler Agriculture Limited | Manufacturing | 2021 |
| James Howley Engineering Ltd | Professional & scientific | 2021 |
| James Mackle (U.K.) Limited | Manufacturing | 1991 |
| James Rust Design Ltd | Professional & scientific | 2018 |
| JAN & Jore Ltd | Transport & logistics | 2019 |
| Jarrtech Ltd | Agriculture & fishing | 2024 |
| Jary Developments Ltd | Construction | 2018 |
| JAS Electrical Contractors Limited | Construction | 2016 |
| JAS Insulation Solutions Ltd | Construction | 2025 |
| Jase Plant & Equipment Hire Ltd | Construction | 2023 |
| Jasmas Properties Ltd | Real estate | 2023 |
| Jasmine Nursery Limited | Wholesale & retail | 2003 |
| Jatec Healthcare Ltd | Health & social care | 2023 |
| Jatec Ltd | Other services | 2017 |
| Javelin Retail Limited | Wholesale & retail | 2002 |
| Jazzy D Balloons Ltd | Wholesale & retail | 2015 |
| JB Bikes Limited | Wholesale & retail | 2016 |
| Jbam Properties Limited | Real estate | 2022 |