| James Perry Associates Limited | Professional & scientific | 2014 |
| James Roofing Ltd | Construction | 2005 |
| James Sharp Planning Limited | Professional & scientific | 2018 |
| James Simmons SET Construction Ltd | Construction | 2018 |
| Jamieison Limited | Wholesale & retail | 2019 |
| Jamo Printing Ltd | Manufacturing | 2021 |
| Jamo Solutions Ltd | Manufacturing | 2015 |
| Janatti MGT Limited | Manufacturing | 2013 |
| Janded Ltd. | Wholesale & retail | 2015 |
| Jane Knight Enterprises Ltd | Financial services | 2020 |
| Jane Knight Properties Ltd | Administrative & support | 2020 |
| Janie Roxburgh Limited | Other services | 2022 |
| Jansids Limited | Information & communication | 2021 |
| JAS Landmark Group Ltd | Real estate | 2024 |
| Jasgeo Ltd | Real estate | 2019 |
| Jasmine Bromley Limited | Other services | 2023 |
| Jasmine Direct Limited | Wholesale & retail | 2016 |
| Jasper Jasper Ltd | Professional & scientific | 2018 |
| Jasper Trading UK Limited | Other services | 2009 |
| Jasper's Catering Franchise Ltd | Hospitality | 2006 |
| Jaspers Corporate Catering Limited | Hospitality | 2003 |
| Jass Works Limited | Construction | 2026 |
| Javelin International Ltd | Administrative & support | 2023 |
| Jaydas Ltd | Administrative & support | 2020 |
| Jayen Consulting Africa Ltd | Professional & scientific | 2019 |
| Jayen Consulting Ltd | Professional & scientific | 2017 |
| Jaynya Ltd | Health & social care | 2013 |
| Jays Travel Limited | Administrative & support | 2021 |
| Jayvi Transport Limited | Transport & logistics | 2024 |
| JAZ Property Development Limited | Real estate | 2022 |
| JB Global Assets Limited | Real estate | 2022 |
| JB Invest Ltd | Real estate | 2025 |
| JB Lift Services Limited | Manufacturing | 2013 |
| JBF Carpentry and Joinery Limited | Manufacturing | 2020 |
| JBG Consults Ltd | Professional & scientific | 2021 |
| Jbjs Events Ltd | Administrative & support | 2015 |
| JBL Construction Management Limited | Construction | 2020 |
| JBN Solutions Ltd | Health & social care | 2025 |
| JC Audio Ltd | Information & communication | 2016 |
| JC Projects Kent Ltd | Construction | 2026 |
| JC Tech UK Limited | Construction | 2019 |
| JC5 Electrical Services Limited | Construction | 2022 |
| Jcosts Limited | Information & communication | 2015 |
| Jcsalmon International Limited | Administrative & support | 2023 |
| Jcst the Ship Limited | Hospitality | 2025 |
| Jcwc Ltd | Professional & scientific | 2010 |
| JD Swimming Pools Ltd | Administrative & support | 2013 |
| Jdcm Properties Limited | Real estate | 2017 |
| Jdcreations Limited | Construction | 2018 |
| JDM (Petts Wood) LLP | | 2012 |
| JDM Estate Agents Limited | Real estate | 2022 |
| JDW Carpentry Limited | Manufacturing | 2025 |
| Jeffries Arena Ltd | Health & social care | 2014 |
| Jemma Hatt Ltd | Information & communication | 2018 |
| Jems Infra Ltd | Real estate | 2020 |
| Jenicare Limited | Health & social care | 2026 |
| Jenner Business Services Limited | Administrative & support | 2003 |
| Jenner Properties Limited | Real estate | 2017 |
| Jensen Associates Ltd. | Professional & scientific | 2001 |
| Jenson Healthcare Limited | Financial services | 2026 |
| JER Professional Cleaning Limited | Administrative & support | 2023 |
| Jerkin' Around Ltd | Wholesale & retail | 2019 |
| Jerseyman Films Ltd | Information & communication | 2020 |
| JES Construction & Maintenance Services Ltd | Construction | 2026 |
| JES Construction & Maintenance Ltd | Construction | 2021 |
| Jess Medical Ltd | Health & social care | 2017 |
| JET Cleaning London Ltd | Administrative & support | 2013 |
| JET Co. London Ltd | Transport & logistics | 2025 |
| JET SET67 Ltd | Administrative & support | 2025 |
| Jetrec Ltd | Information & communication | 2024 |
| Jetsam DS Ltd | Professional & scientific | 2026 |
| Jetéclat Ltd | Administrative & support | 2025 |
| Jewelsbymanroop Ltd | Wholesale & retail | 2024 |
| JFM Allstars Ltd | Administrative & support | 2020 |
| JG Properties Management Limited | Real estate | 2018 |
| Jg&A Limited | Real estate | 2020 |
| JGC Trading Limited | Wholesale & retail | 2012 |
| JGI Property Ltd | Real estate | 2022 |
| JH Bromley Ltd | Real estate | 2021 |
| Jhaqk Creative Group Ltd | Arts & recreation | 2017 |
| Jiayu Limited | Wholesale & retail | 2017 |
| Jibs Consulting Limited | Health & social care | 2014 |
| Jicontracts Limited | Administrative & support | 2025 |
| Jill Hardy Services Ltd | Administrative & support | 2024 |
| Jing CAI Arts Ltd | Wholesale & retail | 2024 |
| Jinnah & Co Ltd | Professional & scientific | 2010 |
| JJ Associates Ltd | Health & social care | 2018 |
| JJ Property Networks Ltd | Hospitality | 2024 |
| JJ WES Ltd | Wholesale & retail | 2025 |
| JJA Scaffolding Ltd | Construction | 2016 |
| JJB TEC Ltd. | Construction | 2018 |
| JJK Services (Kent) Limited | Financial services | 2016 |
| JJL Enterprise Ltd | Education | 2025 |
| JJM Healthcare Ltd | Health & social care | 2021 |
| JKG Organic Limited | Manufacturing | 2017 |
| JKL Residential Ltd | Real estate | 2026 |
| Jksp Properties Ltd | Real estate | 2023 |
| JL Allen Limited | Wholesale & retail | 2020 |
| JLB Steels Limited | Construction | 2021 |
| Jlinks Physiotherapy Limited | Health & social care | 2019 |