| Jagir Builder Ltd | Construction | 2022 |
| Jahangirnagar University Alumni Association in UK (Juaauk), Bangladesh Ltd | Other services | 2018 |
| Jahaw Ltd | Wholesale & retail | 2021 |
| Jahn RAD Ltd | Real estate | 2024 |
| Jaigauriganesh Consulting Services Limited | Information & communication | 2018 |
| Jaime Cotton Ltd | Education | 2025 |
| Jaipur Limited | Extraterritorial | 1999 |
| Jaipur Pink Limited | Extraterritorial | 1996 |
| Jajove Ltd | Administrative & support | 2022 |
| Jake C & Sons Limited | Manufacturing | 2026 |
| Jake Ocean Integrated Systems Limited | Construction | 2026 |
| Jakins Trees Limited | Wholesale & retail | 1982 |
| Jalal Auto International Ltd | Wholesale & retail | 2009 |
| Jalian Enterprises Ltd | Wholesale & retail | 2023 |
| Jaltek Holdings Limited | Financial services | 2014 |
| Jaltek Systems Limited | Manufacturing | 1988 |
| Jama Developments Limited | Real estate | 1998 |
| Jamaican Jerk and Burger HUT Ltd | Hospitality | 2020 |
| Jamak Bricks Ltd | Construction | 2025 |
| Jamal Habib Enterprises Ltd | Wholesale & retail | 2025 |
| Jamal Store Ltd | Wholesale & retail | 2021 |
| Jamb Productions Limited | Construction | 2022 |
| James Clarke Transpersonal Psychology LLP | | 2025 |
| James Estates (Properties) Limited | Construction | 2022 |
| James Estates (Southern) Limited | Construction | 2018 |
| James Estates (Toddinton) Limited | Real estate | 2022 |
| James Estates Construction Ltd | Construction | 2026 |
| James Estates Cotswolds Homes Limited | Construction | 2024 |
| James Estates Cotswolds Homes Three Ltd | Construction | 2025 |
| James Estates Cotswolds Homes Two Ltd | Construction | 2025 |
| James Estates Holdings Limited | Construction | 2022 |
| James Laurence Investments Limited | Other services | 2015 |
| James Leonard Designs Ltd | Wholesale & retail | 2021 |
| James Place Management Company Limited | Households | 2017 |
| James Walsh Accountant Limited | Professional & scientific | 1997 |
| James Walsh Limited | Professional & scientific | 2007 |
| Jamia Academy Luton Ltd | Education | 2024 |
| Jamie's Lawn Care Ltd | Administrative & support | 2022 |
| Jamjap Academic Creative Empire Limited | Manufacturing | 2021 |
| Jammy Nana's Ltd | Hospitality | 2018 |
| Jamoy Autoworkz Ltd | Wholesale & retail | 2021 |
| Jamrock Media CIC | Education | 2019 |
| Jamuna Express Limited | Transport & logistics | 2018 |
| Jamuna Nodi Ltd | Hospitality | 2014 |
| JAN Autos Limited | Wholesale & retail | 2012 |
| Janaan Photo & Films Ltd | Information & communication | 2024 |
| Janet Marsh Recruitment Services Ltd | Administrative & support | 2023 |
| Jangid Hospitality Ltd | Hospitality | 2025 |
| Jani Motors Limited | Wholesale & retail | 2024 |
| Janitorial Warehouse Ltd | Wholesale & retail | 2014 |
| Jannat Associates Ltd | Wholesale & retail | 2017 |
| Jannat Catering Ltd | Hospitality | 2023 |
| Jannat Supermarket Limited | Wholesale & retail | 2025 |
| Jans Property Management Ltd | Construction | 2023 |
| Jantan Properties Limited | Construction | 2006 |
| Jantrah Tech Ltd | Information & communication | 2025 |
| Japji Buillder Ltd | Construction | 2025 |
| Japjifleet UK Ltd | Administrative & support | 2026 |
| Jaral Traders Ltd | Wholesale & retail | 2022 |
| Jarby Projects Ltd | Information & communication | 2019 |
| Jarco Eats Ltd | Hospitality | 2025 |
| Jarco Foods Ltd | Hospitality | 2024 |
| Jarmanjit Singh Ltd | Construction | 2026 |
| Jaro Construction Ltd | Construction | 2009 |
| Jaro Haulage Limited | Transport & logistics | 2016 |
| Jarral Motors Limited | Wholesale & retail | 2012 |
| Jarral Trading Ltd | Wholesale & retail | 2025 |
| Jarrett Industries (UK) Limited | Manufacturing | 2017 |
| JAS Emporium Ltd | Wholesale & retail | 2025 |
| JAS Finchley Stores Limited | Wholesale & retail | 2012 |
| JAS Retail Solutions Ltd | Wholesale & retail | 2023 |
| JAS2 Construction Ltd | Construction | 2021 |
| Jase Management Ltd | Administrative & support | 2020 |
| Jasey Casey Ltd | Extraterritorial | 2021 |
| Jashandeep Construction UK Ltd | Construction | 2022 |
| Jasim&Co Ltd | Transport & logistics | 2022 |
| Jasmin Xpress Ltd | Hospitality | 2025 |
| Jasmine Care Limited | Health & social care | 2025 |
| Jason Haulage Ltd | Transport & logistics | 2019 |
| Jassu Clothing Store Ltd | Wholesale & retail | 2026 |
| Jast Holdings Ltd | Other services | 2018 |
| Jasvir Services Limited | Construction | 2017 |
| Jata Brickwork Ltd | Construction | 2024 |
| Jata Property Management Limited | Real estate | 2026 |
| Jauk Consultancy Limited | Information & communication | 2013 |
| Javaid Investments Ltd | Real estate | 2017 |
| Javed Consultants Limited | Professional & scientific | 2012 |
| Javed Properties Luton Ltd | Real estate | 2023 |
| Javelin Cars Limited | Administrative & support | 2007 |
| JAW Construction Limited | Construction | 2012 |
| JAW Global Venture Resources Limited | Hospitality | 2024 |
| Jawani Limited | Arts & recreation | 2023 |
| Jaxa Transport Limited | Transport & logistics | 2018 |
| JAY & Co Lettings Ltd | Real estate | 2025 |
| JAY & LEO Management and Letting Company Limited | Real estate | 2016 |
| JAY Barbering Ltd | Other services | 2025 |
| JAY GEE Sparks Limited | Construction | 2019 |
| JAY Innovations Limited | Transport & logistics | 2023 |
| JAY Jalaram Property Ltd | Real estate | 2024 |
| JAY Sparks Ltd | Construction | 2012 |