| Independent Energy Consultants Limited | Professional & scientific | 2013 |
| Indian Habibi Ltd | Hospitality | 2023 |
| Indieair Limited | Energy | 2026 |
| Indomh Food Services Ltd | Hospitality | 2025 |
| Infinity Outlet Limited | Administrative & support | 2021 |
| Informe Pilates Ltd | Arts & recreation | 2025 |
| Inge Louise Ltd. | Professional & scientific | 2016 |
| Inhightnd Ltd | Professional & scientific | 2026 |
| Injured Jockeys Company Limited | Wholesale & retail | 1971 |
| Innersoul Ltd | Arts & recreation | 2022 |
| Innominate Limited | Professional & scientific | 2007 |
| Inspire Social Care Services (Newmarket) Limited | Health & social care | 2020 |
| Inspired Services Publishing Limited | Information & communication | 2007 |
| Intelligeania Limited | Hospitality | 2012 |
| Interaxtion Limited | Information & communication | 1998 |
| International Racing Bureau Limited | Administrative & support | 1977 |
| International Transport Services Limited | Transport & logistics | 2018 |
| Intrepid Inns Limited | Hospitality | 2014 |
| Inventive Media Publishing Limited | Administrative & support | 2007 |
| Invincible Ltd | Other services | 2026 |
| IO Limited | Extraterritorial | 2007 |
| Iota Accountancy Services Limited | Manufacturing | 2009 |
| Iotica Consultants Ltd | Professional & scientific | 2022 |
| Ipswich Escape Rooms Limited | Arts & recreation | 2016 |
| Ironsmith Technologies Ltd | Professional & scientific | 2015 |
| IRT Manor Farm Ltd | Real estate | 2024 |
| Irt(Gb) Ltd | Administrative & support | 2019 |
| IS Support Services Ltd | Wholesale & retail | 2023 |
| Isard Ltd | Extraterritorial | 2025 |
| Isis (NKT) Ltd | Other services | 2013 |
| Isle of Wight Hideaways Limited | Extraterritorial | 2020 |
| Isofield Limited | Wholesale & retail | 2021 |
| IT Genetics Limited | Professional & scientific | 2011 |
| IV Ltd | Extraterritorial | 2009 |
| IVANOV92 Ltd | Construction | 2016 |
| Ivas Electrical Limited | Construction | 2018 |
| Ivydene Trading Limited | Water & waste | 2026 |
| IW Ltd | Extraterritorial | 2009 |
| Ixer Communications Ltd | Professional & scientific | 2025 |
| J & J Owen Holdings Limited | Financial services | 2020 |
| J & J Owen Properties Limited | Real estate | 2025 |
| J & P Building Services Ltd | Construction | 2020 |
| J a Ryan Plumbing & Heating Limited | Construction | 2010 |
| J Button Construction Limited | Construction | 2011 |
| J C M Property Maintenance Ltd | Households | 2002 |
| J Crowther Landscapes Limited | Administrative & support | 2017 |
| J Doswell Carpentry and Building Services Ltd | Construction | 2006 |
| J J Brickwork Contractor Ltd | Construction | 2021 |
| J P Compton Horsebox Services Ltd | Wholesale & retail | 2009 |
| J R Brickwork Ltd | Construction | 2014 |
| J R Developments (London) Ltd | Construction | 2023 |
| J S & H Engineering Ltd | Wholesale & retail | 2022 |
| J T Response Limited | Information & communication | 1996 |
| J T Wayne Utilities Limited | Construction | 2024 |
| J W Mclaren & Sons Limited | Agriculture & fishing | 2011 |
| J Wallis Electrics Limited | Construction | 2023 |
| J&B Stores Limited | Wholesale & retail | 2024 |
| J&T Luxury Apartments Ltd | Real estate | 2019 |
| J. Sharp Nutrition Limited | Wholesale & retail | 1997 |
| J. Turner Construction Limited | Construction | 2018 |
| JA International Limited | Administrative & support | 2017 |
| JA Ltd | Extraterritorial | 2020 |
| JAC Whymbishe Ltd | Hospitality | 2023 |
| Jack Jones Racing Ltd | Agriculture & fishing | 2022 |
| Jack Ross Fitness Ltd | Arts & recreation | 2019 |
| Jacob PUB Company Ltd | Hospitality | 2025 |
| Jaggard Brothers Motor Vehicle Engineers Limited | Wholesale & retail | 2003 |
| Jagger Designs Ltd | Manufacturing | 2026 |
| James Bailey Planning Limited | Professional & scientific | 2019 |
| James D Teale Services Ltd | Information & communication | 2024 |
| James Knight Plant Hire Limited | Construction | 1996 |
| James Owen Racing Limited | Other services | 2015 |
| James Tate Racing Limited | Arts & recreation | 2011 |
| Jamm Express UK Ltd | Transport & logistics | 2023 |
| JAN Pantasri Limited | Professional & scientific | 2025 |
| Janah Management Company Limited | Transport & logistics | 1988 |
| Jannah Curry Ltd | Hospitality | 2018 |
| Jansen Recruitment Services Ltd | Administrative & support | 2019 |
| January Ltd | Extraterritorial | 2023 |
| Jasmine and Myrtle Properties Ltd | Real estate | 2024 |
| Jason Weaver Limited | Other services | 1995 |
| Jaxdene Solutions Limited | Transport & logistics | 2014 |
| JCS Automotive Limited | Manufacturing | 2011 |
| JD Hire Services Limited | Transport & logistics | 2015 |
| JDH Electrics Ltd | Construction | 2018 |
| JE Ltd | Extraterritorial | 2009 |
| Jeavons Lane Owners Limited | Real estate | 2008 |
| Jedge Property Management Limited | Real estate | 2026 |
| Jefferson Close Consulting Ltd | Professional & scientific | 2024 |
| Jetshine Solutions Ltd | Administrative & support | 2025 |
| JFA Consultancy Services Limited | Administrative & support | 2019 |
| JG Paediatrics Limited | Health & social care | 2020 |
| JH Carpentry Limited | Construction | 2025 |
| JIC Properties Ltd | Real estate | 2024 |
| JIF Sports Limited | Arts & recreation | 2025 |
| Jill Lamb Bloodstock Limited | Administrative & support | 2009 |
| JIM Brownbridge Limited | Construction | 2016 |
| Jimmy Quinn Ltd | Arts & recreation | 2009 |
| JJ Confederation Ltd | Other services | 2024 |
| JJ Space Management Limited | Professional & scientific | 2021 |