| Jenga Assets Limited | Real estate | 2024 |
| Jenga Court Limited | Real estate | 2016 |
| Jenga Developments Limited | Real estate | 2019 |
| Jenga House Harrow Residential Management Limited | Real estate | 2016 |
| Jenga House Limited | Real estate | 2014 |
| Jenga Investments Limited | Real estate | 2024 |
| Jenga Limited | Real estate | 2003 |
| Jennifer's Nails Ltd | Other services | 2010 |
| Jenpak Limited | Hospitality | 2012 |
| Jepwey Properties Limited | Construction | 1956 |
| Jermyn Securities Limited | Real estate | 1987 |
| Jessie Properties Ltd | Real estate | 2022 |
| JET Constructions London Ltd | Construction | 2018 |
| JET Farmers Limited | Professional & scientific | 2012 |
| Jetmark Limited | Administrative & support | 2006 |
| Jewish Camp USA Limited | Extraterritorial | 2020 |
| Jewish Camps USA Limited | Education | 2017 |
| Jewish Counsellors USA Limited | Extraterritorial | 2018 |
| Jewish Leaders USA Limited | Extraterritorial | 2020 |
| Jewish Volunteers USA Limited | Extraterritorial | 2021 |
| Jeyandra Legal Limited | Public administration | 2025 |
| JF & Partners Ltd | Real estate | 2019 |
| JG Advisory Ltd | Professional & scientific | 2020 |
| JG Rattigan Ltd | Construction | 2014 |
| Jghr Consulting Ltd | Administrative & support | 2017 |
| JHG Watches Limited | Extraterritorial | 2015 |
| Jibble Group Ltd | Financial services | 2021 |
| Jibble Ltd | Information & communication | 2021 |
| Jigsaw Estate Planning Ltd | Administrative & support | 2020 |
| Jigsaw Wealth Management Ltd | Financial services | 2020 |
| JIT Grab Services Limited | Water & waste | 2022 |
| JIT Patel Consultancy Services Limited | Professional & scientific | 2012 |
| Jiyarchi Trading Limited | Transport & logistics | 2020 |
| JJ Carpentry Ltd | Manufacturing | 2020 |
| JJS Flooring Limited | Wholesale & retail | 2025 |
| JKL Contractors Ltd | Construction | 2025 |
| JKP Services Ltd | Construction | 2022 |
| JKS Assets Limited | Real estate | 2026 |
| JKS Care Limited | Real estate | 2025 |
| JL Lofts Ltd | Construction | 2020 |
| JLS Contracts Ltd | Construction | 2023 |
| JM Liquor Land Ltd | Wholesale & retail | 2023 |
| Jmar Creative Limited | Professional & scientific | 2016 |
| Jmlk Ltd | Real estate | 2024 |
| JMP Technologies Ltd | Wholesale & retail | 2012 |
| JMR Financial Consultancy Ltd | Professional & scientific | 2011 |
| JMS & Partners Ltd | Real estate | 2019 |
| Jnana Sky Limited | Information & communication | 2022 |
| JNV Real Estates Ltd | Real estate | 2020 |
| JNZ Consulting Limited | Professional & scientific | 2012 |
| JO Bangles Limited | Extraterritorial | 1987 |
| JO Leslie Communications Limited | Professional & scientific | 2005 |
| JO Palmer Consultants Limited | Information & communication | 2012 |
| JOA Consultants Ltd | Professional & scientific | 2025 |
| Jobling Financial Solutions Limited | Financial services | 2012 |
| John & Delphine Limited | Information & communication | 2014 |
| John Beslali (Jewellery) Limited | Wholesale & retail | 1986 |
| John Brumfit & Radford Tobacco Limited | Wholesale & retail | 1970 |
| John Deehan Photography Ltd | Professional & scientific | 1999 |
| Johnny Security Limited | Administrative & support | 2014 |
| Johny's Brickwork Ltd | Construction | 2021 |
| Joinpath Limited | Information & communication | 1995 |
| Jonathan Kaye Limited | Professional & scientific | 2013 |
| Jonathan Knight Sculpture Ltd. | Arts & recreation | 2007 |
| Jonespartners Ltd | Professional & scientific | 2022 |
| Jonner Construction Limited | Manufacturing | 2025 |
| Joomp CIC | Education | 2019 |
| Jordan Xavier Children's Homes Ltd | Health & social care | 2025 |
| Jordan Xavier Childrens Homes Birmingham Ltd | Health & social care | 2026 |
| Jordan Xavier Childrens Homes NW London Ltd | Health & social care | 2026 |
| Jordan Xavier Connect Ltd | Health & social care | 2023 |
| Jordan Xavier Ltd | Health & social care | 2004 |
| Jorj Rail Limited | Construction | 2014 |
| Journalistic Way Limited | Education | 2021 |
| Journey to Independence Limited | Health & social care | 2017 |
| Joy Accessories Ltd | Wholesale & retail | 2019 |
| Joyfulflowers Ltd | Wholesale & retail | 2020 |
| JP and RP Properties Limited | Other services | 2016 |
| JP Aspire Consulting Limited | Administrative & support | 2019 |
| JP Medical Ltd | Administrative & support | 2009 |
| JP Publishing Group Ltd | Information & communication | 2019 |
| JPA Group Holdings Limited | Professional & scientific | 2022 |
| JPA Property Consultants Limited | Professional & scientific | 2026 |
| JPA Property Developments Limited | Real estate | 2022 |
| Jpdk Property Holdings Ltd | Real estate | 2018 |
| JR Property Management Limited | Construction | 2010 |
| JR UK Services 2 Ltd | Wholesale & retail | 2024 |
| JR UK Services Ltd | Wholesale & retail | 2018 |
| JR71 Ltd | Wholesale & retail | 2025 |
| JRD Global Investments Ltd | Real estate | 2015 |
| JRD Global Services Ltd | Transport & logistics | 2013 |
| JS ALI Consultancy Limited | Other services | 2018 |
| JS Property London Ltd | Real estate | 2025 |
| JS Roofcare Limited | Construction | 2025 |
| JSE Property Holdings Ltd | Real estate | 2022 |
| Jskdirect Ltd | Wholesale & retail | 2023 |
| Jsmarkets Ltd | Wholesale & retail | 2022 |
| Jstp Limited | Real estate | 2025 |
| JTA Property Ltd | Real estate | 2018 |
| Jubilee Cars Stanmore Limited | Transport & logistics | 2025 |