| Jarvis Home Services Ltd | Construction | 2022 |
| JAS IT UP Limited | Wholesale & retail | 2020 |
| Jasman Developments Limited | Real estate | 1984 |
| Jasmine Leisure Ltd | Real estate | 1997 |
| Jass Group Limited | Hospitality | 2025 |
| Jauvla Estates Limited | Real estate | 2015 |
| Javalin Network Services Limited | Other services | 1986 |
| JAW Enterprises Ltd | Construction | 2026 |
| Jaxon Zyre Ltd | Wholesale & retail | 2026 |
| JAY Building Services Limited | Construction | 2000 |
| JAY Geek Ltd | Information & communication | 2024 |
| Jay's Engineering Limited | Manufacturing | 2000 |
| Jaycal Limited | Administrative & support | 2020 |
| Jaydee Consultancy Limited | Information & communication | 2001 |
| Jaydee First Ltd | Real estate | 2020 |
| Jaynesis Care Services Limited | Health & social care | 2023 |
| Jazibimran Limited | Wholesale & retail | 2026 |
| Jazlashes Ltd | Wholesale & retail | 2023 |
| Jazz Limited | Health & social care | 2007 |
| JB Contentlab Ltd | Information & communication | 2025 |
| JB Interiors & Stays. Ltd | Construction | 2025 |
| Jbds Ltd | Construction | 2004 |
| JBM NA Limited | Information & communication | 2023 |
| JBS Supply Chain Planning Limited | Professional & scientific | 2001 |
| JC Kitchens (Sudbury) Limited | Manufacturing | 2005 |
| JCJ Properties Limited | Real estate | 2025 |
| Jcousins Ltd | Administrative & support | 2025 |
| JDG Management Company Limited | Real estate | 1988 |
| JDK Associates Limited | Information & communication | 1998 |
| JED Traders Ltd | Administrative & support | 2022 |
| Jeff Bradley Financial Advisers Ltd | Professional & scientific | 2003 |
| Jehovah Business and Property Services Limited | Real estate | 2005 |
| Jennie Evans Ltd | Manufacturing | 2002 |
| Jeroen Limited | Information & communication | 2025 |
| Jeshen Properties Limited | Real estate | 2024 |
| Jesmond Garage Limited | Wholesale & retail | 2006 |
| Jessie’S Home Care Limited | Public administration | 2024 |
| Jest UK Limited | Other services | 2001 |
| Jesus Must BE Seen Outreach Limited | Other services | 2026 |
| Jewellz Limited | Hospitality | 2017 |
| Jfdi Consultancy Limited | Professional & scientific | 2002 |
| JG Pluck General Building Company Limited | Construction | 2006 |
| Jgyamfi Limited | Health & social care | 2019 |
| Jhol Enterprises Limited | Wholesale & retail | 2026 |
| JIA DUA BAO Supermarket Limited | Wholesale & retail | 2022 |
| JIA Solutions Ltd | Wholesale & retail | 2025 |
| JIF Training and Placement Limited | Administrative & support | 2023 |
| Jigsaw Money Management Ltd | Financial services | 2006 |
| Jilton Holdings Limited | Real estate | 2023 |
| JIM Store Ltd | Wholesale & retail | 2024 |
| Jimmy PUN China Town Limited | Wholesale & retail | 2022 |
| Jinguo Trading Ltd | Wholesale & retail | 2025 |
| Jinqunzhang Ltd | Wholesale & retail | 2023 |
| Jizo Ltd | Administrative & support | 2022 |
| JJ Social Limited | Wholesale & retail | 2026 |
| JJ Watson Heating Limited | Construction | 2022 |
| Jj's Motor Cycles Limited | Wholesale & retail | 2000 |
| JJC Creative Design Limited | Other services | 2019 |
| JK Construction (UK) Limited | Construction | 2002 |
| JL Bespoke Interiors Limited | Construction | 2019 |
| JL Recruitment Services Ltd | Administrative & support | 2025 |
| Jlcross Limited | Real estate | 2018 |
| JM Asbestos Surveyors Limited | Professional & scientific | 2007 |
| JM Group Contracts Ltd | Construction | 2021 |
| JMA Refinishers Limited | Wholesale & retail | 2006 |
| JMC Electrical Testing Services Limited | Manufacturing | 2007 |
| JMK Consulting Ltd | Education | 2006 |
| JMW Accounting Solutions Ltd | Information & communication | 2007 |
| Jmwoodard Corporation Limited | Financial services | 2014 |
| Jobappliq Limited | Information & communication | 2025 |
| Jobserve USA Limited | Professional & scientific | 2006 |
| Joed Health Care Limited | Health & social care | 2014 |
| Johal Medical Limited | Health & social care | 2025 |
| John and Sarah Kemble Limited | | 1986 |
| John F Hunt Power Group Limited | Extraterritorial | 2017 |
| John F. Jossaume Limited | Manufacturing | 1982 |
| John Fisher Limited | Administrative & support | 2002 |
| John Hunter & Associates Limited | Professional & scientific | 2007 |
| John Lawson's Circus Limited | Arts & recreation | 2006 |
| John Moore Property Services Ltd | Real estate | 2006 |
| John R.Keys & Co. Limited | Real estate | 1962 |
| John Read Consultancy Limited | Wholesale & retail | 2001 |
| John Reynolds Carpentry Services Limited | Construction | 2004 |
| John Sharp & SON Ltd | Agriculture & fishing | 2004 |
| John Smith & Co. (London, E.) Limited | Extraterritorial | 1997 |
| Johnson Catering Limited | | 1982 |
| Jolly and Mathew Co Ltd | Health & social care | 2024 |
| Jonahid Management Ltd | Professional & scientific | 2024 |
| Jonathan David Limited | Wholesale & retail | 2005 |
| Jones & Sons Carpets & Blinds Ltd | Wholesale & retail | 2000 |
| Jordaan Limited | Information & communication | 2007 |
| Jordan James Limited | Construction | 1994 |
| Jordan Renovations Ltd | Construction | 2007 |
| Josanns Services Limited | Administrative & support | 2021 |
| Joseph Elliot (Sheffield) Limited | Manufacturing | 1927 |
| Joslin & Co Ltd | Professional & scientific | 2003 |
| Joule Point Residents Association Limited | Households | 2006 |
| Journey IT Forward Ltd | Information & communication | 2023 |
| Journey to Clarity Ltd | Professional & scientific | 2025 |
| Joy & Co (Accountants) Limited | Professional & scientific | 2007 |