| Jackhill Limited | Hospitality | 2021 |
| Jackson Embalming Ltd | Other services | 2023 |
| Jackson Ground Maintenance Limited | Administrative & support | 2006 |
| Jackson LEE Accountants Ltd | Professional & scientific | 2016 |
| Jackson LEE Advisory Ltd | Professional & scientific | 2026 |
| Jackson LEE Holdings Ltd | Professional & scientific | 2026 |
| Jacob's Ladder Property Consultancy Ltd | Real estate | 2014 |
| Jacques Solutions Limited | Administrative & support | 2019 |
| Jadsuk Limited | Wholesale & retail | 2025 |
| Jaevo Ltd | Wholesale & retail | 2026 |
| Jafri Car Sale Ltd | Wholesale & retail | 2025 |
| Jafs Contract Beds Limited | Wholesale & retail | 2016 |
| JAJ Hires Ltd | Administrative & support | 2025 |
| Jakaranda Tree Ltd | Professional & scientific | 2010 |
| Jakerma Holdings Ltd | Financial services | 2020 |
| JAM Business Consulting Limited | Information & communication | 2023 |
| JAM Distributions Ltd. | Wholesale & retail | 2022 |
| JAM Properties & Lettings Limited | Real estate | 2024 |
| JAM3 Partners Ltd | Real estate | 2024 |
| James Grace Holdings Limited | Financial services | 2024 |
| James Grace Limited | Construction | 2011 |
| James Grace Retreats Limited | Real estate | 2024 |
| James Hartley (Skip Hire) Limited | Other services | 1991 |
| James Sharp & Co LLP | | 2018 |
| JAN (Lancs) Ltd | Hospitality | 2017 |
| JAN Group Ltd | Wholesale & retail | 2025 |
| JAN Japan Motor Ltd | Wholesale & retail | 2025 |
| JAN Japan UK Ltd | Wholesale & retail | 2025 |
| Janustech Limited | Manufacturing | 2006 |
| Japanese Knotweed Solutions Limited | Water & waste | 2002 |
| Jaqs Professional Limited | Wholesale & retail | 2014 |
| Jared Integrated Ltd | Construction | 2025 |
| Jaru Investments Limited | Real estate | 2022 |
| JAS 313 Ltd | Real estate | 2024 |
| Jas-Tek Ltd | Wholesale & retail | 2010 |
| Jasal Properties Ltd | Real estate | 2023 |
| Jason Packaging LLP | | 2002 |
| Javtex Limited | Wholesale & retail | 2020 |
| JB Autospares Ltd | Wholesale & retail | 2014 |
| JB Electrician (NW) Ltd | Construction | 2025 |
| Jb-Eye Holdings Ltd | Financial services | 2021 |
| Jb-Eye Ltd | Construction | 2001 |
| Jbbk Ltd | Professional & scientific | 2026 |
| JBC Estates Limited | Real estate | 2020 |
| JBS Paints Ltd | Wholesale & retail | 2023 |
| JBS Waste Removals Limited | Water & waste | 2026 |
| JC Turbines Ltd | Wholesale & retail | 2018 |
| JCB Property Services Ltd | Real estate | 2018 |
| Jcft CIC | Health & social care | 2020 |
| JCL Group Ltd | Real estate | 2016 |
| Jclub Ltd | Households | 2023 |
| JD Controls Ltd | Manufacturing | 2003 |
| JD Housing Development Ltd | Construction | 2021 |
| JD Newco 2 Limited | Administrative & support | 2020 |
| JD Outdoors Holdings Limited | Financial services | 2024 |
| JD Property Limited | Financial services | 2000 |
| JD Sports Active Limited | Professional & scientific | 2015 |
| JD Sports Fashion Europe Holdings Limited | Transport & logistics | 2024 |
| JD Sports Fashion Holdings Limited | Professional & scientific | 2024 |
| JD Sports Fashion PLC | Wholesale & retail | 1985 |
| JD Sports Gyms Acquisitions Limited | Arts & recreation | 2010 |
| JD Sports Gyms Limited | Arts & recreation | 2013 |
| JD Telecoms Solutions Ltd | Wholesale & retail | 2021 |
| JDH Clerical Limited | Administrative & support | 2026 |
| JDS Architects Limited | Financial services | 2022 |
| Jeffreys Consultancy Ltd | Professional & scientific | 2023 |
| Jemm Properties Limited | Financial services | 2024 |
| JEN Parry Consulting Ltd | Administrative & support | 2022 |
| Jenkins Design Services Limited | Professional & scientific | 1979 |
| Jenner Property Company Limited | Real estate | 2024 |
| Jennings Investors Limited | Professional & scientific | 2019 |
| JEP Alternative Provision Limited | Education | 2025 |
| Jerrold Holdings Ltd | Extraterritorial | 2006 |
| Jessica Claire Motion Limited | Information & communication | 2021 |
| Jessica Kate Hair, Beauty & Nails Ltd | Other services | 2025 |
| Jessicathedoula Ltd | Education | 2025 |
| Jets Holdings Limited | Real estate | 2024 |
| JETS2 Holdings Limited | Real estate | 2024 |
| Jewel in the Crown Bury Ltd | Hospitality | 2024 |
| JF Link 2 (UK) Limited | Real estate | 2026 |
| JF Securities Ltd | Real estate | 2004 |
| JF Sellers Limited | Agriculture & fishing | 2021 |
| Jfas Holdings Limited | Financial services | 2021 |
| JFR Financial Solutions Limited | Transport & logistics | 2020 |
| JFS Mortgage Services Limited | Financial services | 2008 |
| JFS Projects Limited | Construction | 2024 |
| JG Plumbing & Maintenance Ltd | Construction | 2024 |
| JG Professional Services Limited | Professional & scientific | 2009 |
| JH Lettings Ltd | Real estate | 2007 |
| JH Opticare Ltd | Health & social care | 2024 |
| JH Property Repairs Ltd | Construction | 2022 |
| JHB Logistics (NW) Limited | Extraterritorial | 2020 |
| JHW Properties NW Ltd | Real estate | 2024 |
| Jignet Limited | Wholesale & retail | 2025 |
| Jigsaw.Coach Ltd | Other services | 2025 |
| Jinnah Day Care Centre | Health & social care | 2002 |
| JJ Electrical and Data Ltd | Construction | 2023 |
| JJ Leisure & Entertainment Ltd | Hospitality | 2023 |
| JJR Commercial Repairs Ltd | Wholesale & retail | 2018 |
| Jjrd Limited | Hospitality | 2018 |