| Jansb Services Limited | Administrative & support | 2017 |
| JAO Environmental Health Consultancy Ltd | Professional & scientific | 2023 |
| Japanese Mary Poppins Ltd | Education | 2019 |
| JAR Productions (Worldwide) Ltd | Arts & recreation | 2025 |
| Jarvis Developments LLP | | 2010 |
| Jarvis Land UK Limited | Professional & scientific | 2005 |
| Jasan Holdings Ltd | Financial services | 2023 |
| Jashmoz Limited | Health & social care | 2025 |
| Jason Aiken Electrical Contractors Ltd | Construction | 2013 |
| Jason Ross Services Limited | Professional & scientific | 2016 |
| Jasper Alliance London Limited | Professional & scientific | 2013 |
| Jast Solutions Ltd | Professional & scientific | 2025 |
| Javab Limited | Hospitality | 2025 |
| Javiso Limited | Professional & scientific | 2016 |
| JAW Technical Services Ltd | Construction | 2025 |
| JAY Diagnostic Ultrasound Limited | Professional & scientific | 2023 |
| JAY Lighting Limited | Construction | 2024 |
| Jay's Care Services Limited | Administrative & support | 2022 |
| JAY3 Homes Limited | Real estate | 2022 |
| Jaymac Engineering Ltd | Construction | 2016 |
| Jayo Limited | Wholesale & retail | 2016 |
| Jayo Transport Limited | Extraterritorial | 2018 |
| Jays Associates Limited | Administrative & support | 2012 |
| Jays Roofing Ltd | Construction | 2023 |
| Jayson Fong Ltd | Professional & scientific | 2020 |
| JAZ & Sons Properties Limited | Real estate | 2017 |
| Jazz Retail Ltd | Wholesale & retail | 2026 |
| JB and SM Homes Limited | Construction | 2019 |
| JB Ashford Ltd | Wholesale & retail | 2026 |
| JB Bookkeeping Services Limited | Administrative & support | 2011 |
| JB Business Consultancy Ltd | Transport & logistics | 2014 |
| JB Electrical Compliance Ltd | Construction | 2014 |
| JB Grimes Associates Ltd | Professional & scientific | 2019 |
| JB Mead Electrical Contractors Limited | Construction | 2023 |
| JB Remedial Farriers Ltd | Agriculture & fishing | 2026 |
| JB Tree and Garden Services Ltd | Agriculture & fishing | 2026 |
| Jb's Halal Meat Ltd | Wholesale & retail | 2025 |
| Jb's Premier Limited | Wholesale & retail | 2024 |
| Jbag Properties Ltd | Real estate | 2025 |
| Jbastien Capital Ltd | Professional & scientific | 2025 |
| JBC Plumbing & Heating Ltd | Construction | 2024 |
| JBC Trading Limited | Wholesale & retail | 2013 |
| JBL Civil Engineering Limited | Construction | 2023 |
| JBM Brickwork Ltd | Construction | 2024 |
| Jbvi Limited | Health & social care | 2022 |
| JC Property Group Limited | Real estate | 2024 |
| JCC Carpentry Ltd | Construction | 2018 |
| JCL Invest Ltd | Real estate | 2021 |
| JCP Construction Services Ltd | Construction | 2019 |
| JCP Homes Ltd | Construction | 2019 |
| Jcservices Ltd | Other services | 2013 |
| JD Medical Consulting Limited | Health & social care | 2018 |
| JD Roofing and Guttering Ltd | Construction | 2025 |
| JD Sales Solutions Limited | Administrative & support | 2019 |
| JDF Group Limited | Extraterritorial | 2018 |
| JDF Holdings Ltd | Financial services | 2020 |
| JDF Refrigeration Ltd | Professional & scientific | 2026 |
| JDT Logistics Ltd | Administrative & support | 2013 |
| JDZ Development Limited | Administrative & support | 2017 |
| Jean Read Education Resourcing Limited | Education | 2010 |
| JEC Compliance Ltd | Construction | 2024 |
| Jeerfw Property Limited | Real estate | 2025 |
| Jeet Convenience Store Ltd | Wholesale & retail | 2023 |
| Jeevanjali Property Ltd | Real estate | 2023 |
| Jelerang Limited | Information & communication | 2004 |
| Jemel One Five Ltd | Information & communication | 2022 |
| JEN Contractors Ltd | Administrative & support | 2011 |
| Jenco Electrical Limited | Construction | 2014 |
| Jenkins Buildings and Brickwork Limited | Construction | 2019 |
| Jenkinson Estates Ltd | Real estate | 2000 |
| Jennifer Campbell Interiors Limited | Professional & scientific | 2014 |
| Jennifer JAY Designs Ltd | Information & communication | 2015 |
| Jennis & Warmann Ltd | | 2015 |
| Jennybaby Ltd | Health & social care | 2021 |
| Jepson Computing Consultants Limited | Information & communication | 1994 |
| Jery Homes Private Limited | Real estate | 2024 |
| Jery Varghese Ltd | Administrative & support | 2017 |
| Jessen James International Ltd | Financial services | 2024 |
| Jessen James Ltd | Administrative & support | 2024 |
| Jetconic Homes Ltd | Construction | 2020 |
| Jetgrain Limited | Administrative & support | 2004 |
| Jetstar Services Limited | Wholesale & retail | 1995 |
| Jetz Ltd | Administrative & support | 2025 |
| JF Decor Ltd | Construction | 2023 |
| JFA Services (Kent) Ltd | Wholesale & retail | 2021 |
| Jfpi Consultancy Services Limited | Professional & scientific | 2018 |
| JFV Ltd | Health & social care | 2019 |
| JGM Consultants Limited | Professional & scientific | 2014 |
| JGP Interim Ltd | Construction | 2019 |
| Jgre Consulting Limited | Professional & scientific | 2025 |
| JGZ Limited | Health & social care | 2016 |
| JH Marketing (Midaf) Limited | Wholesale & retail | 2000 |
| JH Roofing (Kent) Ltd | Construction | 2022 |
| JH Roofing (South East) Limited | Construction | 2025 |
| JH93 Property Management Ltd | Real estate | 2026 |
| Jhalak Ltd | Real estate | 2023 |
| JHL Maintenance Limited | Construction | 2020 |
| JHS Consulting Limited | Education | 2011 |
| JHS Spedition Limited | Transport & logistics | 2022 |
| Jhscook Limited | Professional & scientific | 2023 |