| James HAY Wrap Nominee Company Limited | Professional & scientific | 2010 |
| James Meering Limited | Real estate | 2018 |
| James Street and Picton Place Tenants Maintenance Association Limited | Households | 1974 |
| James Winby Furniture Limited | Administrative & support | 2009 |
| Jamesonkempsey LLP | | 2012 |
| Jamie Coreth Limited | Arts & recreation | 2018 |
| Jamie Martin Consulting Ltd | Professional & scientific | 2015 |
| JAN Care Limited | Health & social care | 2013 |
| Jane Brooks Gym and Swim Ltd | Education | 2023 |
| Jane Harwood Limited | Wholesale & retail | 2005 |
| Janes Limited | Construction | 1986 |
| Jangleshop Records Limited | Information & communication | 2025 |
| Janspeed Technologies Limited | Manufacturing | 2005 |
| Jarred Bundy Construction Limited | Construction | 2008 |
| Jarrett Furniture Ltd | Wholesale & retail | 2015 |
| Jarvis Law Limited | Professional & scientific | 2020 |
| Jasmine Tomms Limited | Extraterritorial | 2014 |
| JAT Associates Ltd | Real estate | 2021 |
| JAY KAY Consolidated Ltd | Manufacturing | 2025 |
| Jayex Technology Limited | Information & communication | 2005 |
| JB Physiology Limited | Health & social care | 2024 |
| JBB Consultancy Limited | Real estate | 2021 |
| JBL Solutions Ltd. | Extraterritorial | 1999 |
| Jblk Consultancy Services Limited | Professional & scientific | 2024 |
| JC Commercial Flooring Limited | Construction | 2025 |
| JC Contracts & Projects Ltd | Professional & scientific | 2025 |
| JC Homes (South) Limited | Real estate | 2022 |
| JCF Property Management Limited | Administrative & support | 2009 |
| JCH Enterprises Limited | Administrative & support | 2011 |
| JCM Fencing Limited | Administrative & support | 2008 |
| JCR Performance Ltd | Wholesale & retail | 2025 |
| JCR Tiling LLP | | 2007 |
| Jdmabb Services Ltd | Public administration | 2024 |
| Jeanne Ricketts Limited | Arts & recreation | 2021 |
| Jelly Farming Limited | Agriculture & fishing | 2021 |
| Jelly Invest Limited | Professional & scientific | 2017 |
| Jelly Property Limited | Real estate | 2017 |
| Jellymark Limited | Professional & scientific | 2017 |
| Jems Estates Limited | Real estate | 2020 |
| Jeni and J Retail Limited | Wholesale & retail | 2022 |
| Jennys 2024 Ltd | Hospitality | 2024 |
| Jensen Yachting Limited | Professional & scientific | 2013 |
| JEP Cleaning Services Ltd | Administrative & support | 2026 |
| Jeremy Holt Ltd. | Real estate | 1993 |
| Jeslock Limited | Real estate | 2013 |
| Jessica Brown Limited | Arts & recreation | 2004 |
| Jetley Consulting Ltd | Professional & scientific | 2025 |
| Jewellery Discovery Limited | Wholesale & retail | 2015 |
| Jf-B Limited | Health & social care | 2005 |
| JFY Services Limited | Professional & scientific | 2006 |
| JG Finance Consultants Limited | Financial services | 2009 |
| Jgharrington Properties Ltd | Real estate | 2026 |
| JGP Lakedale Limited | Construction | 1994 |
| JHG Property Management & Design Ltd | Real estate | 2018 |
| JHM Furniture Limited | Wholesale & retail | 2025 |
| JHM Homes Limited | Real estate | 2023 |
| JHM Sanghera Limited | Transport & logistics | 2018 |
| JIM Buckley & Associates Ltd. | Professional & scientific | 2015 |
| Jiray Ltd | Wholesale & retail | 2025 |
| JJ Beauty and Body Ltd | Other services | 2024 |
| JJ Bryan Enterprises Limited | Real estate | 2014 |
| JJ Worm Limited | Real estate | 2022 |
| Jjabc Limited | Financial services | 2022 |
| JJC Plumbing Limited | Construction | 2015 |
| JJNF1 Ltd | Financial services | 2025 |
| JJPO1 Ltd | Construction | 2025 |
| JJR (GB) Ltd | Information & communication | 2014 |
| JJS Property Ltd | Real estate | 2021 |
| Jjsp Ltd | Real estate | 2021 |
| JJT Projects Ltd | Mining & quarrying | 2020 |
| Jjtactical LLP | | 2013 |
| JK Rugby Coaching & Mentoring Ltd | Education | 2020 |
| Jkcarpetsandflooring Ltd | Wholesale & retail | 2013 |
| Jkgumm Ltd | Administrative & support | 2018 |
| Jkhl Trustees (a) Ltd | Professional & scientific | 2023 |
| Jkhl Trustees (B) Ltd | Professional & scientific | 2023 |
| Jklm Eyecare Limited | Wholesale & retail | 2018 |
| JL Horology Ltd | Wholesale & retail | 2025 |
| JMF Heating and Plumbing Ltd | Construction | 2018 |
| JMG Creative Print Limited | Administrative & support | 2011 |
| JMG Technical Limited | Other services | 2012 |
| JMH Elite Plumbing and Heating Ltd | Construction | 2018 |
| Jmlc Plumbing & Heating Ltd | Construction | 2023 |
| JMP Architecture Ltd | Professional & scientific | 2023 |
| JO Dean Cafe Ltd | Hospitality | 2026 |
| JO Nielsen Limited | Wholesale & retail | 2003 |
| Johe Ltd | Health & social care | 2025 |
| John Ayrton Ltd | Professional & scientific | 2014 |
| John Clark Way Management Company Limited | Households | 2011 |
| John Fairey Will Trustee Limited | Professional & scientific | 2021 |
| John Jeffery (Auctioneers) Limited | Wholesale & retail | 1986 |
| John Jeffery (Holdings) Limited | Wholesale & retail | 2021 |
| John Musgrave Consulting Ltd | Professional & scientific | 2021 |
| John Packer Limited | Wholesale & retail | 1994 |
| John Read Partnership (the) | | 1967 |
| John Rodon Limited | Construction | 2017 |
| John Schroder (Trustees) Limited | Administrative & support | 1993 |
| John the Handyman Ltd | Manufacturing | 2024 |
| John Turner Kitchens & Bathrooms Limited | Construction | 2004 |
| John Woolley Limited | Real estate | 2016 |