| Jamcamservices Limited | Construction | 2024 |
| James Bambi Projekt Limited | Construction | 2021 |
| James Ware & Associates Limited | Professional & scientific | 2015 |
| Jamtechit Limited | Information & communication | 2025 |
| Janet Health Care Ltd | Health & social care | 2021 |
| Janet MAY Properties Ltd | Real estate | 2022 |
| Janjua Logistics Ltd | Wholesale & retail | 2023 |
| Jans Solutions Ltd | Administrative & support | 2019 |
| JAP Homes Ltd | Construction | 2022 |
| Japatrans Ltd | Transport & logistics | 2011 |
| Japsule Ltd | Wholesale & retail | 2025 |
| JAR N JAE Ltd | Manufacturing | 2025 |
| Jarara Limited | Hospitality | 2017 |
| JAS 62 Ltd | Transport & logistics | 2025 |
| JAS United Limited | Real estate | 2022 |
| Jasmann Limited | Real estate | 2010 |
| Jasmanvir Ltd | Information & communication | 2026 |
| Jasminnie Tiney Home Ltd | Health & social care | 2025 |
| Jawia Ltd | Transport & logistics | 2020 |
| JAYDEN247SERVICES Ltd | Real estate | 2024 |
| Jayhan Consulting & Training Ltd | Professional & scientific | 2026 |
| Jaysanneel Limited | Wholesale & retail | 2026 |
| JB East Limited | Real estate | 2020 |
| JB Philips Group Ltd | Administrative & support | 2025 |
| JBH Sheet Metal Fabrications Ltd | Manufacturing | 2019 |
| JCA Capital Limited | Professional & scientific | 2015 |
| JCL Facilities Limited | Construction | 2014 |
| JCL Ltd | Information & communication | 2015 |
| JD Heating & Cooling Ltd | Construction | 2025 |
| JDC Group Holdings Ltd | Financial services | 2021 |
| JDC Property Group Ltd | Real estate | 2021 |
| JDS Business Limited | Administrative & support | 2026 |
| JDS Electrical Contracts Limited | Construction | 2018 |
| JDW Capital Holdings Limited | Real estate | 2026 |
| JE Flight Training Limited | Professional & scientific | 2024 |
| Jeaon Limited | Construction | 2017 |
| Jeatt Mediation and Consulting Ltd | Professional & scientific | 2025 |
| JEE Contact Services Ltd | Health & social care | 2019 |
| Jeet Transport Ltd | Transport & logistics | 2020 |
| Jeff 68 Ltd | Hospitality | 2016 |
| Jega Care Ltd | Health & social care | 2023 |
| Jelb Enterprises Limited | Hospitality | 2021 |
| Jemark Ltd | Health & social care | 2015 |
| Jemluxx Personal Shopping Ltd | Other services | 2020 |
| Jenkins Formwork Limited | Construction | 2016 |
| Jennytec Limited | Health & social care | 2014 |
| Jenz Housing Ltd | Hospitality | 2025 |
| Jenz Tyres Ltd | Wholesale & retail | 2025 |
| Jerichoctrl Limited | Wholesale & retail | 2024 |
| Jerock Enterprise Ltd | Wholesale & retail | 2023 |
| Jerotec Ltd | Administrative & support | 2021 |
| Jessyjane Limited | Health & social care | 2019 |
| Jeva Fashion Ltd | Wholesale & retail | 2014 |
| Jezreel Designs Limited | Manufacturing | 2019 |
| JH Assessment Consulting Ltd | Administrative & support | 2023 |
| JH Trucking Ltd | Transport & logistics | 2024 |
| Jhonny Trans Ltd | Transport & logistics | 2021 |
| JHONY78 Ltd | Transport & logistics | 2019 |
| Jidel Limited | Other services | 2021 |
| Jimster Ltd | Wholesale & retail | 2023 |
| JJ Gilding Limited | Administrative & support | 2011 |
| JJ Groundworks Limited | Construction | 2014 |
| Jj's Accountancy Ltd | Professional & scientific | 2019 |
| Jjaa Limited | Administrative & support | 2023 |
| JK and Daughter UK Limited | Wholesale & retail | 2021 |
| JK Fried Chicken Limited | Hospitality | 2025 |
| JKN Capital & Property Ltd | Real estate | 2025 |
| JKS Essex Convenience Stores Ltd | Wholesale & retail | 2023 |
| Jldh Ltd | Information & communication | 2019 |
| JLK Consulting Ltd | Health & social care | 2022 |
| JMA Media Ltd | Construction | 2025 |
| Jmash Ltd | Hospitality | 2025 |
| JMC Homes Group Ltd | Real estate | 2025 |
| JMH Safety Services Ltd | Professional & scientific | 2019 |
| JMK London Ltd | Wholesale & retail | 2022 |
| JMZ Engineering Consultancy Limited | Professional & scientific | 2020 |
| JN 91 Ltd | Construction | 2019 |
| JN Asset Management Ltd | Real estate | 2021 |
| JN Capital Ltd | Real estate | 2023 |
| Jnissi Properties Ltd | Real estate | 2023 |
| JO 2 JOS Service Ltd | Real estate | 2021 |
| JO Carpentry Limited | Construction | 2018 |
| JO Daniels Limited | Information & communication | 2015 |
| JO Harrison Ltd | Manufacturing | 2023 |
| Joachim Trans Ltd | Transport & logistics | 2018 |
| Jobinbi Ltd | Health & social care | 2020 |
| Jodas Healthcare Limited | Health & social care | 2019 |
| Jodvie Group Limited | Wholesale & retail | 2022 |
| Joeb Building Services Ltd | Construction | 2026 |
| Joel Property Services Limited | Real estate | 2025 |
| Joeliz & Co Limited | Information & communication | 2007 |
| John & ANA Trans Ltd | Transport & logistics | 2019 |
| John Barberton Ltd | Hospitality | 2019 |
| John F Hunt Group Ltd | Construction | 2006 |
| John F Hunt Limited | Construction | 1981 |
| John F Hunt Power Limited | Administrative & support | 2005 |
| John F Hunt Regeneration Limited | Water & waste | 2011 |
| John F Hunt Residential Limited | Construction | 2015 |
| John F Hunt Trustee Limited | Financial services | 2024 |
| John F. Hunt Developments Ltd | Real estate | 1996 |