| J.M. Osborne & Co. Limited | Professional & scientific | 1998 |
| J.W. Pullen Limited | Construction | 1982 |
| JA Financial Services Limited | Financial services | 2004 |
| Jaanvi Properties Ltd | Real estate | 2025 |
| Jacadi UK Limited | Wholesale & retail | 2021 |
| Jack Kendall Innovations Limited | Information & communication | 2016 |
| Jackson Projects & Design Limited | Construction | 2019 |
| Jack’S Shack Coffee Limited | Hospitality | 2021 |
| Jaego Hair Design Ltd | Other services | 2005 |
| JAG IT Consultancy Ltd | Information & communication | 2022 |
| JAG PM Services Ltd | Professional & scientific | 2012 |
| JAG Property Solutions Ltd | Real estate | 2025 |
| Jago Health Limited | Professional & scientific | 2008 |
| Jamalex Steel Limited | Wholesale & retail | 2015 |
| James Camden Engineering Limited | Manufacturing | 1994 |
| James D Barrett Limited | Professional & scientific | 2018 |
| James Gunn Limited | Information & communication | 2014 |
| James Mann Construction Limited | Construction | 2007 |
| James Rose Painting & Decorating Contractors Limited | Construction | 2012 |
| James Whittle Consulting & Advisory Services Limited | Professional & scientific | 2024 |
| Jamie Cassidy Soccer Schools Limited | Arts & recreation | 2025 |
| Jamie Lloyd Bloodstock Limited | Agriculture & fishing | 2012 |
| Jamin Rally Limited | Administrative & support | 2019 |
| Jane Hood Coaching and Development Solutions Limited | Professional & scientific | 2025 |
| Japan Shop Ltd | Wholesale & retail | 2026 |
| Jasmin Consulting Limited | Professional & scientific | 2023 |
| JB Building & Landscaping Limited | Construction | 2020 |
| JBC Property Developments (ASH Green) Limited | Construction | 2022 |
| JBS Products Limited | Manufacturing | 2009 |
| JC Creates Ltd | Information & communication | 2025 |
| JC HMO Solutions Ltd | Construction | 2025 |
| JC Tennis Limited | Education | 2019 |
| JCD Electrical Services Ltd | Construction | 2016 |
| JCE Capital Ltd | Administrative & support | 2005 |
| Jcrd Limited | Manufacturing | 2014 |
| JDB1 Ltd | Manufacturing | 2024 |
| JDI Creative Solutions Limited | Professional & scientific | 2010 |
| Jeanius Technologies Limited | Information & communication | 2018 |
| Jemlyn Limited | Professional & scientific | 2008 |
| Jenga Industrial Properties Limited | Administrative & support | 2025 |
| Jenny Packwood Consulting Ltd | Professional & scientific | 2026 |
| Jephson Properties Ltd | Construction | 2022 |
| Jepmond Associates Ltd | Professional & scientific | 2017 |
| JES and Sun Ltd | Transport & logistics | 2020 |
| JES Events Ltd | Administrative & support | 2024 |
| Jesa Engineering Ltd | Construction | 2024 |
| Jeso Ltd | Wholesale & retail | 2021 |
| Jessanol Limited | Professional & scientific | 2025 |
| Jetstream England Limited | Information & communication | 2014 |
| Jett Logistics Ltd | Transport & logistics | 2020 |
| Jettender Singh Chandi Ltd | Health & social care | 2025 |
| Jewel Estates Limited | Construction | 2006 |
| JFS Property Solutions Ltd | Real estate | 2025 |
| JFS Transport Solutions Limited | Transport & logistics | 2022 |
| JG Telecoms Limited | Information & communication | 2024 |
| Jiraf Globe Limited | Information & communication | 2022 |
| JJS Design Engineering Limited | Professional & scientific | 2015 |
| JKI Property Ltd | Real estate | 2021 |
| JL Telephone Engineers Limited | Professional & scientific | 2017 |
| Jlbj-Uk Ltd. | Manufacturing | 2014 |
| JLV Limited | Real estate | 2020 |
| JMG Aviation Services Limited | Manufacturing | 2019 |
| JMX Distribution Ltd | Wholesale & retail | 2024 |
| Jncc Holdings Limited | Financial services | 2013 |
| JNF (700) Limited | Administrative & support | 2019 |
| JNJ Financial Management Limited | Financial services | 1984 |
| JO & Co Marketing Limited | Professional & scientific | 2006 |
| JOE Day Loft Control Ltd | Construction | 2026 |
| JOE Day Pest Control Ltd | Administrative & support | 2022 |
| JOE Turner (Equipment) Limited | Wholesale & retail | 1987 |
| Joel Davey Garden Design Ltd | Professional & scientific | 2021 |
| John Bateman Insurance Consultants Limited | Financial services | 1980 |
| John Brown Wheels Limited | Wholesale & retail | 2019 |
| John Cornall Antiques Limited | Wholesale & retail | 2013 |
| John Grimes Sawmills Limited | Extraterritorial | 2018 |
| John Harlow & Associates Limited | Real estate | 2000 |
| John Kirk Consulting Limited | Professional & scientific | 2015 |
| John Mack (Haulage) Limited | Information & communication | 1973 |
| John Pratt Limited | Professional & scientific | 2012 |
| Johnson and Johnson (Cotswolds) Ltd | Construction | 2017 |
| Johnson and Johnson (Stratford) Ltd | Construction | 2020 |
| Johnson and Johnson Builders Limited | Construction | 1975 |
| Joint Project Limited | Manufacturing | 2018 |
| Joint Vision Property Ltd | Real estate | 2015 |
| Jointing Tech Limited | Wholesale & retail | 1988 |
| Jonathan Head Consulting Limited | Administrative & support | 2007 |
| Jonlan Motors Limited | Wholesale & retail | 1995 |
| Jopaz Limited | Professional & scientific | 2023 |
| Josluk Limited | Professional & scientific | 2018 |
| Joymo Sport Media Limited | Information & communication | 2023 |
| Joymo UK Ltd | Information & communication | 2021 |
| JP Aumento Limited | Information & communication | 2011 |
| JP Aumento Real Estate Ltd | Real estate | 2026 |
| JP Motorsports Ltd | Manufacturing | 2019 |
| JPB4R Associates Limited | Professional & scientific | 2017 |
| JQ Business Services Ltd | Professional & scientific | 2021 |
| JRJ Property Management Ltd | Real estate | 2025 |
| JRR Homes Ltd | Real estate | 2020 |
| JS Car Automotive Ltd | Wholesale & retail | 2026 |
| JSA Support Limited | Health & social care | 2012 |