| Jimmy Key Careers Ltd | Administrative & support | 2025 |
| Jimmy's Iced Coffee Limited | Manufacturing | 2010 |
| JJ Bioenergy Limited | Professional & scientific | 2014 |
| JJ Construction Recruitment Ltd | Administrative & support | 2022 |
| JJ G JJ Limited | Wholesale & retail | 2015 |
| JJ Property Developments Limited | Construction | 2017 |
| JJC Autos Limited | Wholesale & retail | 2023 |
| JJC Solutions Limited | Information & communication | 2015 |
| JJJ Forecourt Ltd | Wholesale & retail | 2021 |
| JJM & AAA Properties Ltd | Real estate | 2025 |
| Jjtec Ltd | Administrative & support | 2023 |
| JK Sons Properties Limited | Real estate | 2014 |
| JKF Property Management Ltd | Real estate | 2024 |
| JKR Collective Ltd | Real estate | 2025 |
| JKW Consulting Ltd | Professional & scientific | 2026 |
| JLK Mechanical Ltd | Construction | 2020 |
| JLN Financial Limited | Administrative & support | 2012 |
| Jmagi Properties Ltd | Real estate | 2021 |
| JMC Property Services (UK) Ltd | Administrative & support | 2018 |
| JMD Inns Ltd | Hospitality | 2023 |
| Jmda Interiors Ltd | Construction | 2015 |
| Jmer Limited | Wholesale & retail | 2017 |
| JMI Ventures Limited | Construction | 2024 |
| JMK Construction Ltd | Construction | 2017 |
| JMR Electrical & Mechanical Limited | Construction | 2021 |
| JMR Estates Ltd | Real estate | 2021 |
| JMS Digital Ltd | Wholesale & retail | 2025 |
| JMS Horizon Limited | Information & communication | 2024 |
| JMS Technologies Limited | Information & communication | 2004 |
| Jmss Consulting Ltd | Professional & scientific | 2021 |
| Jmss PH Limited | Real estate | 2026 |
| Jmtech Digital Solutions Limited | Information & communication | 2020 |
| Jmtech Holdings Limited | Financial services | 2025 |
| JN KAV Ltd | Wholesale & retail | 2025 |
| Joan Limited | Extraterritorial | 2024 |
| Joanne Prior Limited | Professional & scientific | 2011 |
| Jobam Accounting and Finance Services Ltd | Financial services | 2025 |
| Jobam Ltd | Wholesale & retail | 2026 |
| JOBNET247 Limited | Information & communication | 2023 |
| Jobshout Limited | Information & communication | 2017 |
| Jodi S Stylehouse Limited | Professional & scientific | 2022 |
| Joent Barbers and Salon Limited | Other services | 2015 |
| Jogabi Limited | Information & communication | 2014 |
| John Bates Inspection Limited | Construction | 2007 |
| John Chaney Decorating Limited | Construction | 2015 |
| John Civil Engineering Limited | Construction | 2016 |
| John D Construction Ltd | Construction | 2022 |
| John D Properties Ltd | Real estate | 2019 |
| John Dennis Road Management Company Limited | Households | 2024 |
| John Dent Services Ltd | Construction | 2019 |
| John Fuller and Partners Limited | Professional & scientific | 2007 |
| John Fyson Limited | Manufacturing | 2024 |
| John Graham-Brown Ltd | Information & communication | 2025 |
| John Hancock Lettings Ltd | Real estate | 2019 |
| John Jones Carpentry Ltd | Construction | 2023 |
| John Parker Group Ltd | Hospitality | 2020 |
| John Parker Maintenance Ltd | Construction | 2020 |
| Jolly and Jollys Limited | Professional & scientific | 2011 |
| Jonas Electricals Ltd | Construction | 2020 |
| Jonas Wells,Limited | Professional & scientific | 1905 |
| Joni Brahaj Limited | Transport & logistics | 2024 |
| Joscalee Limited | Health & social care | 2023 |
| Joseph Cornel Construction Ltd | Construction | 2010 |
| Joseph Paul Mechanical Electrical Services Ltd | Construction | 2024 |
| Josh Chafer Logistics Ltd | Transport & logistics | 2025 |
| Joshua Express Limited | Transport & logistics | 2023 |
| Joshua United Ltd | Construction | 2017 |
| Jotus Ltd | Real estate | 2020 |
| Journeymates Concierge Ltd | Administrative & support | 2025 |
| Joyce O. Community Outreach CIC | Health & social care | 2020 |
| JP Data Services Limited | Information & communication | 2015 |
| JP Global Solutionz Ltd | Wholesale & retail | 2026 |
| JP Kelly Construction Ltd | Construction | 2020 |
| JP Pro Football Limited | Arts & recreation | 2018 |
| JP Racing Ltd | Arts & recreation | 2015 |
| JPB Embedded Solutions Ltd | Information & communication | 2022 |
| JPS IT Ltd | Information & communication | 2004 |
| JR Coaching Ltd | Arts & recreation | 2019 |
| JRH Electrical Limited | Construction | 2008 |
| JRP Electrical Installations Ltd | Construction | 2025 |
| JSV Property Group Ltd | Real estate | 2024 |
| JT SFX Limited | Construction | 2019 |
| JTS Media Ltd | Information & communication | 2024 |
| Jude Keya Limited | Financial services | 2011 |
| Julian Day Cooks Limited | Arts & recreation | 2024 |
| Jull's Fragrances Ltd | Wholesale & retail | 2023 |
| Jumana Architectural Ltd | Wholesale & retail | 2025 |
| Jumbledbrain Ltd | Education | 2019 |
| Jumping Stars Ltd | Education | 2015 |
| Junction Motors Ltd | Wholesale & retail | 2018 |
| June Cory Ltd | Professional & scientific | 2022 |
| Jung Law Limited | Professional & scientific | 2006 |
| Jurajmaria Property Limited | Real estate | 2025 |
| Just Waxing Herts Ltd | Other services | 2024 |
| JUST4CLICKS Ltd | Professional & scientific | 2026 |
| Justin Davies Health & Safety Training Ltd | Public administration | 2023 |
| Justnews Limited | Information & communication | 2021 |
| JVB Travel Ltd | Administrative & support | 2023 |
| JVR Ltd | Extraterritorial | 2024 |
| JW Animations Ltd | Information & communication | 2013 |