| Jev's Detailing and Valeting Limited | Administrative & support | 2025 |
| Jewv Ltd. | Real estate | 2015 |
| JF Financial Management Limited | Professional & scientific | 2012 |
| JF Pharma Ltd | Health & social care | 2022 |
| JFD Consultancy Ltd | Administrative & support | 2019 |
| JFL Electrics Limited | Construction | 2026 |
| JFW Asset Management Limited | Financial services | 2021 |
| JG Educational Consultancy Ltd | Education | 2025 |
| JGA Consulting Ltd | Information & communication | 2024 |
| JGA Editing Limited | Information & communication | 2018 |
| Jgfx Limited | Financial services | 2024 |
| JH Mortgages Limited | Administrative & support | 2021 |
| JH Services London Ltd | Transport & logistics | 2013 |
| Jillyb Enterprises Ltd | Administrative & support | 2016 |
| Jimmi Limited | Hospitality | 2023 |
| Jimmy's Electrics Maintenance Services Ltd | Manufacturing | 2025 |
| Jimmychoi's Limited | Other services | 2014 |
| Jini Solutions Ltd | Professional & scientific | 2018 |
| JJ Auto Cars Ltd | Wholesale & retail | 2026 |
| JJ Boorman Plumbing & Heating Ltd | Construction | 2020 |
| JJ Carpentry & Maintenance Ltd | Construction | 2007 |
| JJ Nails and Beauty Limited | Other services | 2018 |
| JJB (S.E.) Investments Limited | Real estate | 2009 |
| JJD Accountancy Limited | Professional & scientific | 2008 |
| Jjei Management Limited | Professional & scientific | 2022 |
| JJJ Consultancy Ltd | Information & communication | 2014 |
| JJL GAS & Heating Ltd | Construction | 2019 |
| JJT 4 Build Ltd | Construction | 2023 |
| JJW IT Solutions Limited | Information & communication | 2025 |
| Jjwhomes Ltd | Real estate | 2025 |
| JK Events Management and Promotion Limited | Arts & recreation | 2025 |
| JK Finance Business Partners Ltd | Financial services | 2023 |
| JK Plumbing Service Ltd | Construction | 2025 |
| Jk's Grooming Lounge Ltd | Other services | 2025 |
| JKB Property Investment Limited | Real estate | 2023 |
| JKG Developments Limited | Real estate | 2015 |
| JKL Scaffolding Ltd | Construction | 2023 |
| Jkmb Property Investment Limited | Real estate | 2023 |
| Jkss Limited | Real estate | 2021 |
| JL Accounting Solutions Limited | Professional & scientific | 2019 |
| JL Creative Designs Ltd | Information & communication | 2023 |
| JL Properties Management Limited | Real estate | 2019 |
| Jlaser Ltd | Other services | 2018 |
| JLG BTL Ltd | Real estate | 2017 |
| JLG Property Management Ltd | Real estate | 2025 |
| JLL Properties London Ltd | Real estate | 2023 |
| JM Capital Solutions Ltd Limited | Financial services | 2025 |
| JM Cleaning Kent Ltd | Administrative & support | 2016 |
| JM Essential Products Ltd | Wholesale & retail | 2022 |
| JM Gotts Solutions Ltd | Education | 2016 |
| JM Network Solutions Ltd | Information & communication | 2008 |
| JMB Roofers Ltd | Construction | 2025 |
| Jmck Landscapes & Tree Surgery Ltd | Administrative & support | 2024 |
| JMD Electrical Ltd | Construction | 2008 |
| JME Consultancy Services Limited | Professional & scientific | 2018 |
| JMM Consulting Limited | Professional & scientific | 2007 |
| Jmonteon Ltd | Education | 2015 |
| JNB Trading Ltd | Wholesale & retail | 2025 |
| JNJ Building Solutions Limited | Construction | 2014 |
| Jnlcorporation Ltd | Information & communication | 2023 |
| JO Ahmedzai Interior Design Ltd | Professional & scientific | 2021 |
| Joanne Larkam Limited | Health & social care | 2014 |
| Joaq Limited | Administrative & support | 2016 |
| JOE Alves DOC Ltd | Information & communication | 2022 |
| JOE Lewis Goalkeeping Ltd | Professional & scientific | 2023 |
| Joe's Kitchen Ltd | Hospitality | 2025 |
| Joelle's of Chislehurst Limited | Hospitality | 2020 |
| JOHANNA2020 Limited | Health & social care | 2022 |
| John 15 Ltd | Professional & scientific | 2022 |
| John Baker Roofing Limited | Construction | 2015 |
| John Healey & Co Ltd | Administrative & support | 2017 |
| John Overington Painting & Decorating Limited | Construction | 2017 |
| John Roddy Ltd | Construction | 2020 |
| John Tulloch (2008) Limited | Extraterritorial | 2008 |
| JOHN6 Limited | Real estate | 2017 |
| Johnpeter Services Limited | Construction | 2025 |
| Johnston & Johnston Rentals LLP | | 2023 |
| Jojo Jewel Ltd | Manufacturing | 2026 |
| Jojo's Reggae Kitchen Ltd | Hospitality | 2025 |
| Jolker Marine Ltd | Extraterritorial | 2025 |
| Jollof & Jerk Ltd | Wholesale & retail | 2025 |
| Jolly Backs Ltd | Health & social care | 2003 |
| Jolly Hockey Stick Holdings Ltd | Hospitality | 2026 |
| Jolt Academy Limited | Professional & scientific | 2017 |
| Jomoco Consulting Limited | Administrative & support | 2017 |
| JON Lock Creative Limited | Professional & scientific | 2025 |
| JON W Sports Injury Ltd | Administrative & support | 2021 |
| Jonabas Properties Limited | Construction | 2007 |
| Jones & White Services (UK) LLP | | 2024 |
| Jones Nickolds Limited | Professional & scientific | 2012 |
| Joomnet Limited | Information & communication | 2010 |
| Jordan Media Ltd | Professional & scientific | 1999 |
| Jordan Saul Bizzell Design Limited | Professional & scientific | 2016 |
| Joseph & Joseph Property Development Limited | Financial services | 2018 |
| Joseph Alexander Music Ltd | Arts & recreation | 2018 |
| Joseph Leppard Training Limited | Health & social care | 2024 |
| JOSEPH360 Ltd | Real estate | 2025 |
| Jotchit Limited | Information & communication | 2008 |
| Joyce Green Lane Ltd | Construction | 2023 |
| Joyful Party Box Ltd | Wholesale & retail | 2024 |