| JAL Rush Ltd | Wholesale & retail | 2026 |
| Jalet Estates Limited | Real estate | 2017 |
| Jalet Property Services Limited | Real estate | 2017 |
| James Brothers Acquisitions Limited | Financial services | 2025 |
| James Brothers Leeds Limited | Real estate | 2022 |
| James Brothers Properties Limited | Construction | 2015 |
| James Brothers Wellingborough Limited | Real estate | 2016 |
| James Christopher Limited | Administrative & support | 2003 |
| James for Carpets Limited | Other services | 2011 |
| James Lovick Limited | Information & communication | 2015 |
| James Shirley Brand Anddigital Ltd | Professional & scientific | 2025 |
| Jamlin Projects Ltd | Construction | 2025 |
| Jammy Group Holdings Ltd | Financial services | 2023 |
| Jandia Limited | Real estate | 2018 |
| Janine the Travel Director Limited | Administrative & support | 2025 |
| Jannels Consultancy Limited | Professional & scientific | 2019 |
| Jannels Property Holdings Limited | Real estate | 2016 |
| Jard Consulting Limited | Information & communication | 2010 |
| Jasmine Walker Consulting Ltd | Professional & scientific | 2026 |
| JAW Building Services Limited | Construction | 2024 |
| Jayam Software Limited | Information & communication | 2011 |
| Jayess Tools Limited | Manufacturing | 2011 |
| Jays Airports Limited | Transport & logistics | 2009 |
| Jazz and Blues Retreats Ltd | Arts & recreation | 2021 |
| JB & Sons Windows Ltd | Administrative & support | 2022 |
| JB Alexander Limited | Professional & scientific | 2014 |
| JB Care Consultancy Ltd | Health & social care | 2021 |
| JB Manufacturing Ltd | Manufacturing | 2025 |
| JBF Building and Roofing Ltd | Construction | 2023 |
| JBF Healthcare Limited | Health & social care | 2012 |
| JBL Cambridge Ltd | Professional & scientific | 2024 |
| Jbpbsb Ltd | Administrative & support | 2022 |
| JC Engineering Design & Draughting Ltd | Professional & scientific | 2012 |
| JCF Planning Consultancy Limited | Professional & scientific | 2022 |
| JCH Construction Management Services Ltd | Construction | 2025 |
| JCL Electrical Services (UK) Limited | Construction | 2013 |
| JCS IT Solutions Limited | Information & communication | 2011 |
| Jdconstruction Services Ltd | Administrative & support | 2017 |
| JDH 1995 Ltd | Financial services | 2023 |
| JDS Carpets and Flooring Ltd | Wholesale & retail | 2026 |
| JE Locksmith Ltd | Administrative & support | 2019 |
| Jean Lefebvre (UK) Limited | Construction | 1996 |
| JEE Property Ltd | Financial services | 2024 |
| JEH Building Services Limited | Construction | 2015 |
| Jemasys (U K) Limited | Information & communication | 1989 |
| Jemini Services Limited | Wholesale & retail | 2002 |
| JEMZ53 Limited | Financial services | 2022 |
| Jenikov Industries Ltd | Financial services | 2018 |
| Jenikov Ltd | Financial services | 2020 |
| Jenkins Financial Planning Ltd | Financial services | 2012 |
| Jepson Racing Ltd | Arts & recreation | 2022 |
| Jessaka Trading Limited | Wholesale & retail | 1997 |
| Jessica Paice Ltd | Financial services | 2019 |
| Jessie Drea Limited | Agriculture & fishing | 2011 |
| Jeswitha SW Ltd | Information & communication | 2026 |
| JET Applications Limited | Information & communication | 2004 |
| JET One Leisure Ltd | Hospitality | 2025 |
| Jetrun Limited | Transport & logistics | 2014 |
| Jevington Quarry Limited | Real estate | 2015 |
| JEY International Management (UK) Ltd | Information & communication | 2013 |
| JF Pharma Consulting Ltd | Health & social care | 2012 |
| JF Sport and Leisure Ltd | Wholesale & retail | 2025 |
| JFH Investments Limited | Financial services | 2020 |
| JHH Services Ltd. | Professional & scientific | 2013 |
| JHR Care Services Limited | Health & social care | 2022 |
| JJ & EA Property Services Limited | Real estate | 2026 |
| JJ Innovations Limited | Information & communication | 2011 |
| JJ Noma Limited | Financial services | 2025 |
| JJ Reclamation Limited | Water & waste | 2009 |
| JJ Worlds Ltd | Hospitality | 2024 |
| JJD SAS Limited | Wholesale & retail | 2025 |
| JKM North West Properties Limited | Real estate | 2024 |
| JKT Limited | Extraterritorial | 2017 |
| JLM Procurement Consulting Ltd | Professional & scientific | 2017 |
| JMB Properties 1 Limited | Real estate | 2021 |
| JMM Electricservices Ltd | Construction | 2014 |
| JMN Richardson Ltd | Arts & recreation | 2015 |
| JMS (Sussex) Homes Limited | Construction | 2021 |
| JMS Janitorial Supplies Limited | Administrative & support | 1996 |
| JN Building Supplies Ltd | Construction | 2022 |
| JNV Holdings Limited | Financial services | 2020 |
| JO Equi Creative Ltd | Professional & scientific | 2022 |
| JOC Consulting Ltd | Professional & scientific | 2017 |
| Jocoke Capital Limited | Professional & scientific | 2010 |
| Johansson's Cafe Ltd | Wholesale & retail | 2019 |
| John Bird Powered by EXP Limited | Real estate | 2016 |
| John Bull Design Limited | Manufacturing | 2006 |
| John Cameron Ents Limited | Information & communication | 2014 |
| John Cooney Marketing Ltd | Professional & scientific | 2026 |
| John Martin Carpentry & Joinery Services Ltd | Construction | 2021 |
| John Mason Financial Planning Limited | Financial services | 2005 |
| John Nodes & Sons Limited | Real estate | 1937 |
| Johndins Scrumfall Ltd | Information & communication | 2020 |
| Johnny Hire Ltd | Administrative & support | 2018 |
| Johnstone Kemp Tooley (Holdings) Ltd | Financial services | 2011 |
| Johnstone Kemp Tooley Limited | Professional & scientific | 1995 |
| Jolpa Limited | Information & communication | 2019 |
| Jones Shipwrights Limited | Manufacturing | 2025 |
| Jones Total Design Ltd | Professional & scientific | 2020 |
| Joom Digital Limited | Wholesale & retail | 2026 |