| Jandel Autos Service Ltd | Wholesale & retail | 2025 |
| Jandezn Limited | Other services | 2025 |
| Jane Wren Consultancy Ltd | Administrative & support | 2019 |
| Janek Transport Ltd | Transport & logistics | 2025 |
| Janessa & Jedi Facilities Management Limited | Administrative & support | 2026 |
| Jani Communications Limited | Professional & scientific | 2013 |
| Janjoe 123 Limited | Professional & scientific | 2002 |
| Janjua Transport Ltd | Other services | 2024 |
| Janko Construction Ltd | Construction | 2024 |
| Janosik Ltd | Wholesale & retail | 2010 |
| Janus Partnership Limited | Professional & scientific | 2017 |
| JAP IT Services & Consulting Ltd | Information & communication | 2017 |
| Japanese Fusion London Limited | Hospitality | 2025 |
| Japangatewaymotors Ltd | Wholesale & retail | 2025 |
| Jaqueline Sport Ltd | Wholesale & retail | 2018 |
| Jardine Homes Limited | Real estate | 2019 |
| Jardine Stimpson Ltd | Transport & logistics | 2018 |
| Jaret Transport Limited | Transport & logistics | 2017 |
| Jari Logistic Ltd | Transport & logistics | 2021 |
| Jarju and Sons Limited | Health & social care | 2018 |
| Jaros Properties Ltd | Households | 2025 |
| Jartojam Solutions Limited | Administrative & support | 2018 |
| Jaryan Ltd | Health & social care | 2016 |
| Jascia Occupational Health Limited | Health & social care | 2021 |
| Jasmin's House Ltd | Real estate | 2024 |
| Jasmir Ltd | Wholesale & retail | 2024 |
| Jason Lewis Limited | Information & communication | 2021 |
| Jasp Transport Limited | Transport & logistics | 2023 |
| Jass Venues Limited | Hospitality | 2017 |
| Jaswal and Brothers Ltd | Transport & logistics | 2025 |
| Jathu Investments Ltd | Wholesale & retail | 2019 |
| Jatt Properties Limited | Real estate | 2025 |
| Java Mill Investments Limited | Financial services | 2020 |
| Javahub Ltd | Wholesale & retail | 2019 |
| Javenta Limited | Extraterritorial | 2025 |
| Javid & Sons Limited | Real estate | 2025 |
| Javidaan Ltd | Hospitality | 2021 |
| Jawaher Group Limited | Real estate | 2025 |
| Jaxxon Property Group Ltd | Real estate | 2024 |
| Jaxxson Ltd | Information & communication | 2020 |
| JAY Contracts (Pull Tests) Ltd | Other services | 2020 |
| JAY Contracts Fire Protection Ltd | Construction | 2026 |
| JAY Contracts Group Limited | Construction | 2025 |
| JAY Contracts Ltd | Other services | 2017 |
| JAY Gopal Ltd | Wholesale & retail | 2024 |
| JAY Hardwick Scaffolding Ltd | Construction | 2009 |
| JAY Hova Ltd | Wholesale & retail | 2018 |
| JAY R Properties Limited | Real estate | 2011 |
| JAY Wolfe Metalwork Limited | Administrative & support | 2009 |
| Jay's Gents Hair Stylist Ltd | Other services | 2024 |
| Jay's Irepairs Ltd | Wholesale & retail | 2022 |
| Jaya Chandra Ltd | Real estate | 2025 |
| Jayell Consultancy Limited | Construction | 2012 |
| Jayne Asante Mensah Ltd | Health & social care | 2018 |
| Jayne West Photography Ltd | Professional & scientific | 2002 |
| Jaytrac Limited | Administrative & support | 1995 |
| Jaznat Ltd | Health & social care | 2025 |
| JB Care Ltd | Health & social care | 2018 |
| JB Electrical (Northampton) Ltd | Construction | 2025 |
| JB Elite Cleaning Ltd | Administrative & support | 2026 |
| JB Food Takeaway Ltd | Extraterritorial | 2020 |
| JB Global Holdings Group Limited | Financial services | 2025 |
| JB Global Holdings Ltd | Real estate | 2021 |
| JB Global Investments Ltd | Real estate | 2024 |
| JB Medical (London) Limited | Health & social care | 2019 |
| JB Metal Finishers Ltd | Manufacturing | 2017 |
| JB SCS Group Limited | Financial services | 2025 |
| JB Talent Solutions Ltd | Professional & scientific | 2025 |
| JB90 Racing Ltd | Professional & scientific | 2020 |
| Jbfw Limited | Agriculture & fishing | 2021 |
| Jbhogal Property Ltd | Real estate | 2025 |
| JBR Commercial Services Ltd | Administrative & support | 2023 |
| JBS UK Trading Limited | Wholesale & retail | 2022 |
| JBY Couriers Ltd | Transport & logistics | 2023 |
| JC Body Shop Ltd | Wholesale & retail | 2025 |
| JC Construction & Engineering Ltd | Administrative & support | 2019 |
| JC Decorating Ltd | Construction | 2023 |
| JC Nickel Services Ltd | Construction | 2022 |
| JC Plant Hire Ltd | Administrative & support | 2020 |
| JC Rebar Ltd | Construction | 2021 |
| JC Softwash Solutions Ltd | Administrative & support | 2025 |
| JC Tate Holdings Limited | Financial services | 2022 |
| JC Tate Investments Limited | Construction | 2017 |
| JC Tate Properties Limited | Real estate | 2022 |
| JC Tate Trading Limited | Agriculture & fishing | 2022 |
| JCB Scaffolding Services Ltd | Construction | 2026 |
| JCE Collections Limited | Administrative & support | 2019 |
| JCG Carpentry Limited | Extraterritorial | 2006 |
| Jcms Property Ltd | Real estate | 2023 |
| Jcrc Roofing Ltd | Construction | 2016 |
| Jcrm Ltd | Other services | 2021 |
| JCS & Sons Ltd | Transport & logistics | 2018 |
| JCS Sparks Limited | Construction | 2015 |
| JCW Holdings Group Limited | Financial services | 2021 |
| JD Consultants (Wootton) Limited | Professional & scientific | 2024 |
| JD Doran Tarmac and Resin Specialist Ltd | Administrative & support | 2026 |
| JD Glazing Limited | Construction | 2016 |
| JD Grounds & Gardens Limited | Administrative & support | 2024 |
| JD Lakutowicz Ltd | Real estate | 2024 |
| JD Scaffolding Services Ltd | Construction | 2022 |