| JMP (Leeds) Ltd | Hospitality | 2000 |
| JMP (Liverpool) Limited | Hospitality | 2009 |
| JMR Resources Ltd | Administrative & support | 2021 |
| Jmtt Consulting Ltd | Information & communication | 2024 |
| JMW Post Production Ltd | Information & communication | 2022 |
| JN Surprizes Limited | Hospitality | 2020 |
| JNB Fire Limited | Construction | 2023 |
| JNB Fire Servicing Limited | Construction | 2024 |
| Jnjp Properties Ltd | Real estate | 2025 |
| Jnpa Business Venture Limited | Information & communication | 2023 |
| JO JO Taxis Limited | Transport & logistics | 2016 |
| Jo-Jim Consult Limited | Construction | 2024 |
| Joacore Ltd | Health & social care | 2024 |
| Joanna Mcdwyer Limited | Administrative & support | 2021 |
| Joanna Tongue Hair Ltd | Other services | 2019 |
| Joaska Building Contractors Limited | Construction | 2002 |
| Jobs in Maritime Ltd | Administrative & support | 2018 |
| Jobsolve Global Limited | Other services | 2025 |
| JOE Technology Limited | Information & communication | 2022 |
| Joeam Properties Limited | Real estate | 2026 |
| Joel Glass Services Ltd | Construction | 2016 |
| Joel James Consulting Limited | Professional & scientific | 2012 |
| Joemag Computa Ltd | Information & communication | 2018 |
| Joepat Ltd | Construction | 2015 |
| Jofran & Co Ltd | Real estate | 2025 |
| John Browning Builders Limited | Construction | 2003 |
| John Hayward Limited | Wholesale & retail | 2001 |
| John Laing Construction Limited | Construction | 1920 |
| John Laing International Limited | Construction | 1959 |
| John Paul Stephen Limited | Manufacturing | 2025 |
| John Searles Transport Limited | Transport & logistics | 2006 |
| John Spurr Limited | Manufacturing | 2010 |
| John W Groombridge Motorcycles Limited | Wholesale & retail | 2002 |
| Johnjo Social Care Ltd | Health & social care | 2022 |
| Johnsons Direct Limited | Wholesale & retail | 1997 |
| Johnsons Flowers & Plants Limited | Wholesale & retail | 2004 |
| JOHNTOSIN1 Ltd | Health & social care | 2022 |
| Johsan Ltd | Real estate | 2021 |
| Joining Knowledge Ltd | Real estate | 2023 |
| JON & K Limited | Administrative & support | 2025 |
| JON & K Traders Ltd | Wholesale & retail | 2025 |
| Jonathan Drew Ltd | Construction | 2018 |
| Jones Facilities Management Ltd. | Construction | 2011 |
| Jones FM LLP | | 2012 |
| Jones Hospitality Limited | Administrative & support | 2016 |
| Jones Properties Holdings Limited | Real estate | 2026 |
| Jonvero Ltd | Information & communication | 2011 |
| Jools Cleaning Services Limited | Other services | 2015 |
| Jools Management Services Limited | Administrative & support | 2023 |
| Joona Limited | Education | 2010 |
| Joshua Michael Properties Ltd | Real estate | 2020 |
| Joshua Remitt & Associates Limited | Professional & scientific | 2018 |
| Joule Technology Limited | Extraterritorial | 1986 |
| Joyce Green Meadows Properties Residents Association Limited | Households | 2024 |
| Joydens Wood Breakfast and After School Club Ltd | Other services | 2016 |
| Joyner Commercial Vehicles Limited | Wholesale & retail | 2015 |
| Jozars Limited | Professional & scientific | 2025 |
| Jozie Properties Limited | Real estate | 2015 |
| JP Business Consulting UK Ltd | Professional & scientific | 2025 |
| JP Loki Coffee Limited | Hospitality | 2026 |
| JP Plumb Ltd | Construction | 2018 |
| JP Simpson Limited | Administrative & support | 2015 |
| JP19 Ltd | Administrative & support | 2019 |
| JPH Project Solutions Ltd | Construction | 2021 |
| Jpro-Uk Limited | Information & communication | 2020 |
| JPS Advisory Limited | Professional & scientific | 2013 |
| JPS Transit Ltd | Professional & scientific | 2014 |
| JR Prime Properties Ltd | Households | 2024 |
| JR Technical Ltd | Manufacturing | 2020 |
| JRE Services Limited | Construction | 2018 |
| Jressentials.Online Ltd | Wholesale & retail | 2026 |
| Jrip Ltd | Wholesale & retail | 2019 |
| Jrsr Ltd | Professional & scientific | 2018 |
| JS Clearbooks Limited | Professional & scientific | 2024 |
| JS Const Ltd | Construction | 2026 |
| JS Designs (London) Limited | Professional & scientific | 2002 |
| JS Superfoods Ltd | Wholesale & retail | 2018 |
| Jsat Financial Services Ltd | Financial services | 2015 |
| JSC Wellness Limited | Manufacturing | 2025 |
| Jshara Foods Ltd | Hospitality | 2017 |
| JSJ Marketing Solutions Ltd | Professional & scientific | 2019 |
| JSK Dencare Ltd | Health & social care | 2021 |
| JSN Housing Ltd | Real estate | 2019 |
| JSS Investments Group Ltd | Financial services | 2025 |
| JSS Logistics Ltd | Transport & logistics | 2024 |
| Jssk Holdings Ltd | Real estate | 2023 |
| JSV Plumbing and Heating Ltd | Administrative & support | 2016 |
| Jtarawally Ltd | Health & social care | 2024 |
| JTC Construction Ltd. | Construction | 2012 |
| JTM Contracts Ltd | Construction | 2018 |
| JTS Refurbishment Ltd. | Construction | 2008 |
| Jukes Electrical Limited | Energy | 2014 |
| Jukes Partners Limited | Energy | 2014 |
| Juliaba Ltd | Health & social care | 2016 |
| Juliet Jones Ltd | Education | 2023 |
| Juliked Limited | Administrative & support | 2011 |
| Jumesh Services Limited | Health & social care | 2015 |
| Jummyjollof Catering Limited | Hospitality | 2019 |
| Jumping Beans Pre-School Limited | Health & social care | 2012 |
| Jumping Beans Village Preschool Limited | Education | 2022 |