| JAM Tech Group Ltd | Information & communication | 2025 |
| Jamalc Limited | Health & social care | 2020 |
| Jamalils Ltd | Health & social care | 2009 |
| Jambo Transport Ltd | Transport & logistics | 2026 |
| James Aaron Developments Limited | Construction | 2015 |
| James and Company Estate Agents Ltd | Extraterritorial | 2021 |
| James Cargo Fulfilment Ltd | Transport & logistics | 2017 |
| James Cargo Services Limited | Transport & logistics | 1984 |
| James Cochrane Plumbing Services Limited | Construction | 2017 |
| James Gale Property Limited | Administrative & support | 2017 |
| James Mansfield Timber (Properties) Ltd | Real estate | 2015 |
| James Mansfield Timber Limited | Wholesale & retail | 2000 |
| James Optom Limited | Wholesale & retail | 2017 |
| James Thomson Civils Ltd | Construction | 2021 |
| Jamil Kassam Ltd | Information & communication | 2022 |
| Jamleo Consulting Limited | Professional & scientific | 2013 |
| Jamouk Limited | Other services | 2013 |
| JAN Props Ltd | Hospitality | 2023 |
| Janika Holdings Limited | Real estate | 2025 |
| Janshi Properties Limited | Real estate | 2016 |
| Janux Ltd | Information & communication | 2026 |
| Japji Sangha Construction Ltd | Construction | 2026 |
| JAR Group Ltd | Other services | 2023 |
| JAS and Kirat London Ltd | Hospitality | 2026 |
| JAS Building Services Ltd | Construction | 2018 |
| JAS Johal Limited | Arts & recreation | 2010 |
| Jaskar Constructions Ltd | Construction | 2021 |
| Jaskaranpreet Construction 1 Ltd | Construction | 2025 |
| Jasmin Close RTM Company Limited | Professional & scientific | 2006 |
| Jass Transport Services Limited | Transport & logistics | 2025 |
| Jasveen Limited | Wholesale & retail | 2018 |
| Jato Aviation Limited | Transport & logistics | 2000 |
| Jato Dynamics Limited | Professional & scientific | 1988 |
| Jato Japan Limited | Professional & scientific | 1999 |
| Jato Nominees Limited | Extraterritorial | 2017 |
| Jawanda Properties Limited | Real estate | 2021 |
| Jawandha Construction Ltd | Construction | 2026 |
| JAY & Sons Properties Ltd | Real estate | 2020 |
| JAY MAA Kaali Restaurants Limited | Hospitality | 2025 |
| JAY Ramji Solutions Limited | Information & communication | 2015 |
| Jay&H Limited | Wholesale & retail | 2002 |
| Jayaar Enterprises Limited | Real estate | 2018 |
| Jaydeegee Ltd. | Information & communication | 2017 |
| Jaydeen Properties Ltd | Real estate | 2016 |
| Jaygowrie Property Ltd | Real estate | 2021 |
| JAZ Classic Limited | Wholesale & retail | 2019 |
| JAZ Investments Limited | Wholesale & retail | 2017 |
| Jazz Creation Limited | Hospitality | 2025 |
| Jazz Driving School Limited | Education | 2023 |
| Jazz Trans Limited | Transport & logistics | 2026 |
| JB Chinade Ltd | Wholesale & retail | 2024 |
| JB Glazing Ltd | Construction | 2023 |
| Jbluetelford Coffee Limited | Hospitality | 2024 |
| Jbluewednesbury Coffee Ltd | Hospitality | 2025 |
| JBM Estate Management Limited | Construction | 2024 |
| JBS - John Building Service Ltd | Construction | 2013 |
| JBS Durham UK Limited | Financial services | 2017 |
| JBS Global (UK) Limited | Wholesale & retail | 2001 |
| JBS Meat UK Limited | Financial services | 2015 |
| JBS Melwood UK Limited | Financial services | 2020 |
| JC Motors 247 Ltd | Wholesale & retail | 2016 |
| JC Photography Ltd | Professional & scientific | 2025 |
| JC Property London Ltd | Real estate | 2014 |
| JC Sparks Limited | Manufacturing | 2025 |
| JCB Property Investments Limited | Real estate | 2021 |
| Jcbm Solution Limited | Construction | 2026 |
| JD Rail Limited | Construction | 2016 |
| JD30 Homes Limited | Real estate | 2023 |
| JD30 Ltd | Professional & scientific | 2020 |
| JD30 Property Ltd | Financial services | 2021 |
| Jdeep Ltd | Administrative & support | 2024 |
| Jdgh Land Ltd | Real estate | 2018 |
| JDM Assets LLP | | 2026 |
| Jean Page Florist (Online) Ltd | Wholesale & retail | 2023 |
| Jeanette Smart Limited | Extraterritorial | 2024 |
| Jedha Ltd | Administrative & support | 2022 |
| Jedivin Ltd | Hospitality | 2018 |
| Jedt Consultancy Ltd | Professional & scientific | 2017 |
| Jefferson Wells Ltd | Professional & scientific | 1988 |
| Jellypet Ltd | Wholesale & retail | 2025 |
| Jeltek Weatherguard Limited | Extraterritorial | 1931 |
| Jenrick Engineering Limited | Administrative & support | 2001 |
| Jenrick Services Limited | Administrative & support | 1982 |
| Jenrick Technology Limited | Administrative & support | 1984 |
| JEP Infotec Services Limited | Information & communication | 2009 |
| Jeremiahs Limited | Manufacturing | 2014 |
| Jesel Property Ltd | Real estate | 2020 |
| JET Cleaning Service Contractor Ltd | Administrative & support | 2025 |
| JET Interior Services Limited | Manufacturing | 2025 |
| JET RAJ Ltd | Wholesale & retail | 2021 |
| JET Tech Solutions Ltd | Manufacturing | 2025 |
| JEY Property Ltd | Real estate | 2023 |
| JF Wallace Limited | Professional & scientific | 2024 |
| JFH Building Services and Developments Ltd | Construction | 2015 |
| JG &Co Limited | Transport & logistics | 2026 |
| JG Environmental Limited | Other services | 2011 |
| Jgbvms Consulting Ltd | Information & communication | 2021 |
| JGM Investments (UK) Limited | Real estate | 2014 |
| JGM Transport Solutions Limited | Transport & logistics | 2016 |
| JH Food & Wine Limited | Wholesale & retail | 2019 |