| Information Protection Professionals Limited | Administrative & support | 2013 |
| Insight Laboratory Services Limited | Professional & scientific | 2007 |
| Insight Track Limited | Professional & scientific | 2005 |
| Inspired Waterjet Ltd | Manufacturing | 2017 |
| Intelligent Traffic Systems Ltd | Wholesale & retail | 2014 |
| Intelloxx Ltd | Manufacturing | 2024 |
| Interestatepromo Ltd | Real estate | 2019 |
| Interquartz (U K) Limited | Information & communication | 1981 |
| IPM (East) Limited | Professional & scientific | 2004 |
| Iqmet Painting and Roofing Limited | Construction | 2020 |
| Irwin Leasing Ltd | Agriculture & fishing | 2004 |
| Irwin Property Limited | Real estate | 2016 |
| IT Optim Limited | Information & communication | 2023 |
| Ivondra Limited | Transport & logistics | 2025 |
| Ivory House Freehold Limited | Real estate | 2024 |
| IVY UW Limited | Financial services | 2026 |
| J & R Bond Farm Ltd | Agriculture & fishing | 2021 |
| J C Frost & Co Limited | Agriculture & fishing | 2020 |
| J J Boats Limited | Manufacturing | 2006 |
| J J Ellwood Ltd | Real estate | 2025 |
| J Norris Building Services Ltd | Construction | 2017 |
| J Payne Holdings Ltd | Financial services | 2026 |
| J Payne Services Limited | Administrative & support | 2010 |
| J S Hollington Limited | Other services | 2018 |
| J Weller Group Ltd | Transport & logistics | 2021 |
| J.D.Alston(Estates) | Agriculture & fishing | 1946 |
| J.S.G.S.H.A. Group Limited | Extraterritorial | 2022 |
| J.W. Amps Limited | Agriculture & fishing | 1957 |
| Jack Sheppard Ltd | Wholesale & retail | 2010 |
| Jacs Construction Ltd | Construction | 2024 |
| James Osborn Therapy and Coaching Ltd | Health & social care | 2025 |
| James P Dixon Limited | Agriculture & fishing | 2012 |
| Jasinara Limited | Administrative & support | 2010 |
| Jason Gladwin Food Consultancy Ltd | Professional & scientific | 2026 |
| Javimade Solutions Ltd | Transport & logistics | 2025 |
| Jazjem Ltd | Construction | 2016 |
| JC Reclaims and Demolition Limited | Water & waste | 2019 |
| JD Illustrations Ltd | Arts & recreation | 2024 |
| JD Tree Services & Countryside Management Ltd | Agriculture & fishing | 2022 |
| Jelipede Ltd | Professional & scientific | 2023 |
| Jelly JAM Factory Ltd | Households | 2018 |
| Jeremy Green Agricultural Contractor Ltd | Agriculture & fishing | 2010 |
| JEZ Clarke Creative Projects Ltd | Arts & recreation | 2025 |
| Jezcorp Ltd | Wholesale & retail | 2025 |
| JH Risk Ltd | Administrative & support | 2025 |
| JHS Construction Limited | Construction | 2020 |
| JJ Boiler Services Limited | Construction | 2009 |
| JJB Services (UK) Ltd | Professional & scientific | 2013 |
| John DOE Carpets and Furniture Limited | Wholesale & retail | 2004 |
| John Fyfe & SON (ELY) Limited | Agriculture & fishing | 1970 |
| John Hewett Precision Engineering Ltd | Manufacturing | 2015 |
| Johns Taxis (Diss) Limited | Transport & logistics | 2011 |
| Jollof Music & Life Limited | Wholesale & retail | 2025 |
| Jons Games Ltd | Information & communication | 2023 |
| Joseph Wootton & Co Limited | Professional & scientific | 1999 |
| JRM Creative Ltd | Professional & scientific | 2018 |
| Judy Kendrick Marketing Limited | Administrative & support | 2006 |
| Just Another Label Limited | Information & communication | 1998 |
| K Wilby & SON Limited | Construction | 2011 |
| K. G. Read & SON Limited | Construction | 1984 |
| KA Sensors Ltd | Manufacturing | 2006 |
| Kale Property Holdings Limited | Real estate | 2021 |
| KAM Design Solutions Limited | Professional & scientific | 2009 |
| Kangaroo KID Limited | Wholesale & retail | 2025 |
| Karakus Properties Limited | Real estate | 2020 |
| Kate Marshall Garden Design Ltd | Administrative & support | 2023 |
| Keighly Marsh Ltd | Hospitality | 2026 |
| Keith Williams Architects Limited | Professional & scientific | 2001 |
| Kent & Co (Property Management) Limited | Professional & scientific | 2001 |
| Kent Skips Recycling Ltd | Water & waste | 2024 |
| Kenthale Limited | Wholesale & retail | 2011 |
| Kesh & K Retailers Ltd | Wholesale & retail | 2023 |
| Keshwala Investment Ltd | Wholesale & retail | 2023 |
| Kevalan Services Ltd | Construction | 2023 |
| Key Techniques Limited | Information & communication | 1998 |
| Keyroute Limited | Wholesale & retail | 1996 |
| Kindlewood Creative Ltd | Professional & scientific | 2025 |
| Kingfisher Press Holdings Limited | Financial services | 2022 |
| Kingfisher Press Limited | Manufacturing | 2002 |
| Kirsten Works Limited | Professional & scientific | 2013 |
| KJU Maintenance Ltd | Construction | 2017 |
| KM Wealth Management Limited | Financial services | 2020 |
| Konectbus Limited | Transport & logistics | 1996 |
| L a Goddard Properties Limited | Real estate | 2023 |
| L a Hurrell Limited | Construction | 1999 |
| L.R. Wyard-Scott Limited | Wholesale & retail | 1972 |
| L.W. Leeds Limited | Real estate | 1995 |
| LA Health and Wellness Ltd | Other services | 2026 |
| Lake & Pond Aquatics Ltd | Administrative & support | 2022 |
| Lake Solutions (East Anglia) Limited | Agriculture & fishing | 2016 |
| Lamas Holdings Limited | Water & waste | 2018 |
| Lancaster Gate Assistance Ltd | Administrative & support | 2022 |
| Lancaster Gate Services Ltd | Administrative & support | 2022 |
| Lancaster Gate Vehicle Hire Ltd | Administrative & support | 2022 |
| Landforge Limited | Agriculture & fishing | 2024 |
| Landtrac Africa Ltd | Wholesale & retail | 2009 |
| Landup Developments Ltd | Real estate | 2023 |
| Lane Farm Country Foods Limited | Manufacturing | 2012 |
| Lantern Public Relations Ltd | Administrative & support | 2018 |
| Larter & Ford (Ironmongers) Limited | Wholesale & retail | 1991 |