| James Matthew Property Enterprise Limited | Real estate | 2005 |
| James Mcloughlin Ltd | Information & communication | 2024 |
| James Meads Media & Consulting Ltd | Information & communication | 2019 |
| James Mitchell Limited | Wholesale & retail | 2012 |
| James Newman Limited | Manufacturing | 2009 |
| James Nicklin Ltd | Other services | 2022 |
| James Oliver Homes Limited | Real estate | 2025 |
| James Rogers Mechanical Services Limited | Administrative & support | 2016 |
| James Smart & Whitfield Limited | Manufacturing | 1945 |
| James Travel Airfares Limited | Transport & logistics | 1995 |
| James Valeting Services Ltd | Wholesale & retail | 2025 |
| James Walker Goldsmith and Silversmith Limited | Extraterritorial | 1933 |
| James Woolley Consultancy Ltd | Administrative & support | 2026 |
| James, Stanley & Co Limited | Professional & scientific | 2010 |
| Jamesom Ltd | Transport & logistics | 2019 |
| Jameson Motors Ltd | Wholesale & retail | 2019 |
| Jamesons (Tyre) Company Limited | Wholesale & retail | 1973 |
| Jamesons Land Rover Specialist Limited | Wholesale & retail | 2020 |
| Jamesoro Limited | Wholesale & retail | 2026 |
| Jami Mosque & Islamic Centre (Birmingham) Trustees Limited | Other services | 1975 |
| Jamia Alfurqan Limited | Education | 2012 |
| Jamiat UL Muslimin | Other services | 2010 |
| Jamie Flood Photography Ltd | Professional & scientific | 2024 |
| Jamie Oreilly Building Services Ltd | Professional & scientific | 2026 |
| Jamies's Housing Ltd | Health & social care | 2025 |
| Jamil Abedin Investments Ltd | Real estate | 2025 |
| Jamilas Kitchen Ltd | Hospitality | 2017 |
| Jamjams Caribbean Takeaway Limited | Hospitality | 2023 |
| Jamjar Lights Limited | Manufacturing | 2016 |
| Jamkat Group Limited | Professional & scientific | 2018 |
| Jamkat Holdings Limited | Professional & scientific | 2001 |
| Jamkat Trustees Limited | Financial services | 2018 |
| Jammay Group Ltd | Real estate | 2025 |
| Jammm Entertainment Ltd | Arts & recreation | 2024 |
| Jammy BS Ltd | Wholesale & retail | 2026 |
| Jammy Couriers Ltd | Transport & logistics | 2025 |
| Jamo Orthopaedics Ltd | Wholesale & retail | 2024 |
| Jamoon Properties Limited | Real estate | 2018 |
| Jamora Medical Ltd | Health & social care | 2024 |
| Jamrah Travel Ltd | Administrative & support | 2026 |
| Jams Enterprise Ltd | Professional & scientific | 2022 |
| Jams Maintenance Services Ltd | Construction | 2022 |
| Jamsha Ltd | Financial services | 2021 |
| Jamsweeney Limited | Financial services | 2008 |
| Jamuna Auto Ltd | Wholesale & retail | 2024 |
| Jamz International Supermarket Limited | Wholesale & retail | 2026 |
| Jamz Kitchen Limited | Hospitality | 2025 |
| JAN & Co Property Group Ltd | Real estate | 2025 |
| JAN Associates Limited | Wholesale & retail | 2018 |
| JAN Dubiel Ltd | Education | 2023 |
| JAN Holland Limited | Other services | 2011 |
| JAN Juan DE LA Cruz LP | | 2015 |
| JAN London Trade Limited | Wholesale & retail | 2015 |
| JAN Management Services Limited | Households | 2025 |
| JAN Nails & Beauty Suppliers Ltd | Wholesale & retail | 2013 |
| JAN Properties Limited Partnership | | 2016 |
| JAN Ventures Ltd | Wholesale & retail | 2025 |
| Jan&Gu Chai Ltd | Wholesale & retail | 2023 |
| Jan's Hair and Cosmetics Limited | Other services | 2018 |
| Janam Private Ltd | Other services | 2026 |
| Janamir Corporation Ltd | Real estate | 2021 |
| Janan Banqueting Hall Ltd | Other services | 2023 |
| Janan Catering Ltd | Hospitality | 2023 |
| Janan Meat Limited | Wholesale & retail | 1992 |
| Janatha AID Limited | Health & social care | 2022 |
| Janbro Capital Limited | Financial services | 2025 |
| Janda Worldwide Ltd | Real estate | 2022 |
| Jandasec Limited | Other services | 2024 |
| Jandu Associates Bilston Ltd | Wholesale & retail | 2021 |
| Jandu Associates Ltd | Administrative & support | 2011 |
| Jandu Corporation Ltd | Administrative & support | 2012 |
| Jandu Corporation Properties Ltd | Real estate | 2025 |
| Jandu Property Ltd | Real estate | 2024 |
| Jane Brevitt Solicitor LLP | | 2009 |
| Jane Clark Property Ltd | Real estate | 2022 |
| Jane Reynolds Limited | Other services | 2010 |
| Jane Woolrich Beauty Limited | Wholesale & retail | 2019 |
| Jane Woolrich Couture Limited | Manufacturing | 2008 |
| Janelle Care Limited | Health & social care | 2015 |
| Janes Cafe Limited | Hospitality | 2019 |
| Janet Enterprise Ltd | Real estate | 2021 |
| Jangan Brothers Limited | Real estate | 2024 |
| Jango Fashion Trends Ltd | Wholesale & retail | 2026 |
| Jango Transport Ltd | Transport & logistics | 2018 |
| Jania Property Management Ltd | Real estate | 2022 |
| Janitor Experts Ltd | Administrative & support | 2024 |
| Janjoo Digital Limited | Professional & scientific | 2013 |
| Janjoo Solutions Limited | Information & communication | 2011 |
| Janjua Bros Ltd | Wholesale & retail | 2025 |
| Janjua Foods Limited | Wholesale & retail | 2024 |
| Jankconstruction Limited | Manufacturing | 2017 |
| Jankhan Property Group Ltd | Real estate | 2025 |
| Jannah Musk London Ltd | Wholesale & retail | 2023 |
| Jannat Food Services Limited | Wholesale & retail | 2021 |
| Jannath Halesowen Ltd | Hospitality | 2017 |
| Jannatul Travel Ltd | Administrative & support | 2016 |
| Janni Store Ltd | Wholesale & retail | 2025 |
| Janosik Mini Market Ltd | Wholesale & retail | 2021 |
| Janpio Limited | Transport & logistics | 2017 |
| Janr Investments Ltd | Financial services | 2025 |