| JAB Enterprises UK 1 Limited | Manufacturing | 2017 |
| Jack Projects Ltd | Professional & scientific | 2017 |
| Jacob Brookes Ltd | Construction | 2024 |
| Jahg Limited | Extraterritorial | 2022 |
| James Bayliss Carpentry Ltd | Construction | 2018 |
| Jamies Care Solutions Limited | Health & social care | 2017 |
| Japanese Knotweed Surveys Limited | Water & waste | 2013 |
| Jarkopolo Trans Ltd | Transport & logistics | 2014 |
| JAS Business Services Limited | Professional & scientific | 2004 |
| Jbadaventry Ltd | Transport & logistics | 2026 |
| Jbbt Ltd | Manufacturing | 2017 |
| Jbvt Limited | Information & communication | 2012 |
| JC Electrical Contractors Midlands Ltd | Construction | 2020 |
| JCO Automotive Ltd | Wholesale & retail | 2019 |
| JDK Consulting Limited | Professional & scientific | 2010 |
| JDM Pharma Services Ltd | Wholesale & retail | 2022 |
| JDP Consultants Ltd | Professional & scientific | 2012 |
| Jedab Ltd | Other services | 2015 |
| Jefferson Connect Limited | Financial services | 2024 |
| Jefferson Properties Limited | Real estate | 2014 |
| JEM Property Law Consultancy Limited | Professional & scientific | 2014 |
| Jerk Ponde Corner Limited | Hospitality | 2025 |
| Jetboy Productions Ltd | Information & communication | 2023 |
| Jetlag Homes Ltd | Real estate | 2025 |
| JFC Food Limited | Hospitality | 2026 |
| JG Healthcare and Counselling Ltd | Health & social care | 2015 |
| JH Interiors (Midlands) Limited | Construction | 2024 |
| Jickie Limited | Administrative & support | 2012 |
| Jigsaw Group Investments Limited | Financial services | 2024 |
| Jigsaw Urban Design Ltd | Professional & scientific | 2020 |
| JJ Plant Training & Testing Ltd | Construction | 2026 |
| JJ Swim School (Long Buckby) Limited | Education | 2022 |
| JJP Security Ltd | Administrative & support | 2021 |
| JJU Daventry Ltd | Hospitality | 2022 |
| JJW Engineering & Motorsport Limited | Manufacturing | 2015 |
| JKB Productions Ltd | Arts & recreation | 2018 |
| JLR Automation Ltd | Professional & scientific | 2025 |
| JM Weld Limited | Manufacturing | 2021 |
| JMJ Group Limited | Professional & scientific | 2008 |
| JMJ RTK Enterprises UK 2 Limited | Manufacturing | 2017 |
| JN Fabrications Ltd | Manufacturing | 2021 |
| JN Game Farm Ltd | Agriculture & fishing | 2025 |
| Jock Rail Limited | Construction | 2018 |
| JOF COX Racing Ltd | Arts & recreation | 2020 |
| John Robinson Associates Survey Specialists Ltd | Professional & scientific | 2020 |
| JOHN96 Ltd | Transport & logistics | 2019 |
| Johnrishon Limited | Real estate | 2025 |
| Johnson Design and Build Ltd | Construction | 2015 |
| Join Classic (UK) Cultural Development Ltd | Extraterritorial | 2018 |
| Joshua Tucker Photography Ltd | Professional & scientific | 2021 |
| JP Watters Electrical Ltd | Construction | 2025 |
| Jpmpi Limited | Real estate | 2021 |
| JPP (Holdings) Ltd | Financial services | 2016 |
| JPP Construction Management Limited | Professional & scientific | 2025 |
| JPP Consulting Limited | Professional & scientific | 2005 |
| JPP Geotechnical and Environmental Limited | Professional & scientific | 2017 |
| JPP Surveying Limited | Professional & scientific | 2017 |
| JR Press Limited | Manufacturing | 2015 |
| Jrmm Holdings Limited | Financial services | 2021 |
| JSB Compliance Limited | Professional & scientific | 2025 |
| JTK Solutions Limited | Information & communication | 2024 |
| JTS1 Limited | Financial services | 2024 |
| Jubilee Power Plant Ltd | Professional & scientific | 1982 |
| Jufeng Electronic Tech Ltd | | 2013 |
| Juice Sound Limited | Administrative & support | 2017 |
| Junell Maintenance and Repair Ltd | Manufacturing | 2016 |
| Juniper Tree Ltd | Professional & scientific | 2002 |
| Just UK Legal Services Limited | Information & communication | 2012 |
| Justnat Ltd | Transport & logistics | 2021 |
| JWR Finance Ltd | Professional & scientific | 2017 |
| JZ Online Ltd | Wholesale & retail | 2026 |
| K & SO Ltd | Extraterritorial | 2020 |
| K F Drainage Solutions Ltd | Water & waste | 2019 |
| K R Cahill & Co Ltd | Information & communication | 2008 |
| K Ward Furniture Polishers Limited | Other services | 2002 |
| K.C.Carers Limited | Health & social care | 2012 |
| K.P.Landscapes Ltd | Administrative & support | 2017 |
| K1 Composites Ltd | Manufacturing | 2026 |
| K3 Healthcare Ltd | Health & social care | 2015 |
| Kairos 1 Finance Ltd | Financial services | 2025 |
| Kakadu Creative Limited | Professional & scientific | 2013 |
| Kaleb Vieira Racing Limited | Wholesale & retail | 2022 |
| Kalin Transport Ltd | Transport & logistics | 2021 |
| Kamil 1990 Ltd | Wholesale & retail | 2017 |
| Kandm Property Limited | Administrative & support | 2008 |
| Kanflu Hydraulics Limited | Manufacturing | 1988 |
| KAP Consultancy Services Limited | Professional & scientific | 2024 |
| Kapoor Brothers 321 Ltd | Wholesale & retail | 2024 |
| Karan Vhts Limited | Hospitality | 2021 |
| Karibuni Ltd | Administrative & support | 2003 |
| Kate Roberts Consulting Ltd | Professional & scientific | 2020 |
| Katinker Ltd | Extraterritorial | 2023 |
| Kay&Co. Clothing Limited | Wholesale & retail | 2025 |
| KB Book-Keeping Ltd | Professional & scientific | 2011 |
| KBS Paving Services Limited | Construction | 2007 |
| Keba Computer Services Limited | Other services | 2006 |
| Keba Properties Limited | Real estate | 2004 |
| Kelly Family ARK Ltd | Financial services | 2025 |
| Kentbrim Limited | Health & social care | 1987 |
| Kenwood Assets Limited | Financial services | 2024 |