| James Beaufort Limited | Construction | 2013 |
| James Burgwin Limited | Financial services | 2022 |
| James Howell Trading Limited | Financial services | 2026 |
| James Murray Management Ltd | Construction | 2023 |
| James R J Lewis Consulting Limited | Administrative & support | 2017 |
| James Slatford Ltd | Professional & scientific | 2026 |
| James Woods Engineering Limited | Manufacturing | 2017 |
| Jamrokali Ltd | Real estate | 2020 |
| Jarvis Associates Ltd | Information & communication | 2016 |
| Jasmine Hemsley Limited | Other services | 2011 |
| Jathila Transport Ltd | Transport & logistics | 2022 |
| Javelin Design Associates Limited | Manufacturing | 2010 |
| JAY & Robs Windscreens Limited | Wholesale & retail | 2009 |
| JAY3BILL Limited | Administrative & support | 2016 |
| JB Roofing and Leadwork Limited | Construction | 2025 |
| Jbrv Enterprises Limited | Professional & scientific | 2021 |
| JC Homes Developments Ltd | Real estate | 2023 |
| JC Tea Limited | Hospitality | 2024 |
| JCC Property Investments Limited | Real estate | 2025 |
| JCS Solvo Ltd | Professional & scientific | 2026 |
| JDC Advisory Ltd | Professional & scientific | 2024 |
| JDC Paints Ltd | Wholesale & retail | 2018 |
| Jdth Consulting Ltd | Professional & scientific | 2023 |
| Jeffers Consulting Ltd | Professional & scientific | 2024 |
| Jellycode Ltd | Information & communication | 2023 |
| Jems Accountancy Ltd | Extraterritorial | 2014 |
| Jems Bookkeeping & Accountancy Services Ltd | Professional & scientific | 2008 |
| Jems Bookkeeping Ltd | Extraterritorial | 2014 |
| Jems Commercial Investments Ltd | Real estate | 2025 |
| Jems Investments Ltd | Real estate | 2016 |
| Jennings Engineering Supplies Ltd | Professional & scientific | 2011 |
| Jenningsretail Ltd | Wholesale & retail | 2025 |
| Jenrich UK Limited | Wholesale & retail | 2014 |
| Jetmss Leonidakos Ltd | Manufacturing | 2025 |
| Jfcreativeops Ltd | Professional & scientific | 2023 |
| JGB 8TH Global Solutions Ltd | Wholesale & retail | 2018 |
| JGL Construction & Development Limited | Construction | 2021 |
| JH Advisory Services Limited | Professional & scientific | 2025 |
| JH Integrations Ltd | Construction | 2026 |
| JHO Consultancy Limited | Professional & scientific | 2026 |
| JIA London Limited | Real estate | 2019 |
| JIM Hamilton Limited | Professional & scientific | 2025 |
| JJ Networking Ltd | Other services | 2025 |
| JJA Country Construction Ltd | Construction | 2025 |
| JJD Media Ltd | Professional & scientific | 2020 |
| JK Elecserv Limited | Construction | 2026 |
| JK Occupational Health and Safety Consultancy Limited | Professional & scientific | 2026 |
| JK Protection Ltd | Financial services | 2024 |
| JKL Construction & Carpentry Ltd | Construction | 2015 |
| Jkos Media Ltd | Professional & scientific | 2026 |
| Jlcm Property Limited | Real estate | 2022 |
| JMA & Sons Limited | Real estate | 2017 |
| JMF Aviation Consultants Ltd | Professional & scientific | 2014 |
| JMR Financial Ltd | Professional & scientific | 2021 |
| Jncl Ltd | Real estate | 2025 |
| JNE Properties Ltd | Real estate | 2025 |
| JO Painter Ltd | Administrative & support | 2020 |
| Joan of Art Limited | Education | 2022 |
| John Capital Asset Management Ltd | Real estate | 2019 |
| John Monk Assoc Limited | Construction | 2019 |
| John T Porter Services Ltd | Construction | 2014 |
| Jola Learning Ltd | Professional & scientific | 2024 |
| JON Scaffolding Services Ltd | Construction | 2014 |
| Jordan Investments Limited | Real estate | 2016 |
| Joscelyn Yard RTM Company Ltd | | 2025 |
| Josh and Jase Media Ltd | Information & communication | 2023 |
| JP Kolny Ltd | Transport & logistics | 2025 |
| JP Mobile Vehicle Services Limited | Wholesale & retail | 2025 |
| JP Moon Run Limited | Transport & logistics | 2013 |
| Jpjs Services Ltd | Professional & scientific | 2023 |
| JPL Architectural Services Ltd | Professional & scientific | 2024 |
| JRG Limited | Real estate | 2022 |
| Jrls Greens Ltd | Wholesale & retail | 2026 |
| JS Connects Ltd | Wholesale & retail | 2024 |
| JSB Plumbing and Heating Ltd | Construction | 2017 |
| Jsbaker Property Ltd | Households | 2024 |
| JSM Property Consultants Ltd | Real estate | 2025 |
| Jsmc Associates Ltd | Financial services | 2023 |
| JSR Driver Services Ltd | Transport & logistics | 2019 |
| JT Legal Limited | Professional & scientific | 2026 |
| Jubilee Cottage Freehold Limited | Households | 2014 |
| Jubilee Cottage RTM Company Limited | Households | 2011 |
| Juice Publishing Limited | Administrative & support | 2014 |
| Julia Wallis Human Resources Consulting Limited | Professional & scientific | 2006 |
| Julian Hitch Limited | Other services | 2019 |
| June.Limbu.Properties Ltd | Real estate | 2023 |
| Juniper Key Limited | Real estate | 2022 |
| Jusmusic Ltd | Information & communication | 2026 |
| Just Business Advice Ltd | Professional & scientific | 2023 |
| Just DO More Renovations Limited | Construction | 2025 |
| Just LET and Sales Ltd | Households | 2024 |
| Justgym Elite Limited | Arts & recreation | 2016 |
| Justswing Limited | Arts & recreation | 2023 |
| JV Whittaker Properties Ltd | Real estate | 2022 |
| JVE Stores Limited | Wholesale & retail | 2024 |
| JVL Properties Limited | Construction | 2025 |
| JVR Engineering Ltd | Professional & scientific | 2022 |
| K D Electrical Services Limited | Construction | 2009 |
| K U H Limited | Financial services | 1946 |
| K W Interiors Ltd | Construction | 2015 |