| Jahliveforwechildren Limited | Manufacturing | 2019 |
| JAI Therapy Ltd | Health & social care | 2023 |
| Jaizzy Vision Limited | Health & social care | 2022 |
| JAK Property Management Ltd | Real estate | 2022 |
| Jakay Consult Limited | Professional & scientific | 2019 |
| Jakes View Management Limited | Households | 2021 |
| James Houghton Limited | Financial services | 2015 |
| James Raymond Cars Limited | Wholesale & retail | 2009 |
| James, Justina and Ebenezer Limited | Health & social care | 2016 |
| Jamhuri Cultural Vibes CIC | Education | 2026 |
| Jamin Medicals Limited | Health & social care | 2024 |
| Jampal Limited | Real estate | 2024 |
| Jamyne House Limited | Households | 2008 |
| Janetu Medics Limited | Health & social care | 2024 |
| Janken UK Properties Ltd | Real estate | 2023 |
| Janus Medical Research & Chimera Enterprises International Ltd | Professional & scientific | 2012 |
| Janus Property Group Ltd | Real estate | 2023 |
| Japeto Labs Ltd | Information & communication | 2014 |
| Jarda Estate Limited | Real estate | 2024 |
| Jarida Medical Group Ltd | Health & social care | 2026 |
| Jarvis Interiors (Essex) Ltd | Construction | 2022 |
| Jasgo Property Investments Limited | Real estate | 2025 |
| Jasnel Limited | Health & social care | 2016 |
| Javelin (UK) Limited | Administrative & support | 2003 |
| JAY Prime Consultancy Limited | Health & social care | 2023 |
| Jay-Bee Telecom Limited | Wholesale & retail | 2002 |
| Jay-Kay & Ebele Limited | Health & social care | 2024 |
| Jaybee Properties Limited | Real estate | 2019 |
| Jaybim Consult Limited | Professional & scientific | 2016 |
| Jaycompute Consulting Limited | Information & communication | 2017 |
| Jaydock Ltd | Health & social care | 2022 |
| Jaygees Properties Ltd | Real estate | 2025 |
| Jaykay IT Solutions Limited | Health & social care | 2019 |
| Jaynim Ltd | Wholesale & retail | 2024 |
| Jays Motor Services Limited | Wholesale & retail | 2012 |
| Jaysom Ltd | Health & social care | 2024 |
| JAZ Demo Ltd | Construction | 2023 |
| JB Completions Limited | Professional & scientific | 2024 |
| JB Logistic Services UK Ltd | Transport & logistics | 2023 |
| Jbbeauty Group Ltd | Other services | 2026 |
| JBH Solutions Ltd | Construction | 2025 |
| JBZ Limited | Wholesale & retail | 2010 |
| JCC Legal Limited | Professional & scientific | 2025 |
| JCK Roofing Ltd | Construction | 2024 |
| Jcon Support Ltd | Health & social care | 2019 |
| Jdbespokefloors Ltd | Construction | 2026 |
| JDC Daniel Paints Ltd | Construction | 2024 |
| JDS Carpentry & Roofing Ltd | Manufacturing | 2024 |
| Jechso Limited | Extraterritorial | 2013 |
| JED Construction Ltd | Construction | 2021 |
| Jedi Health Ltd | Health & social care | 2024 |
| Jedsa Stores Limited | Wholesale & retail | 2026 |
| Jedtech Limited | Information & communication | 2012 |
| Jehovah Jireh Healthcare Limited | Health & social care | 2015 |
| Jekido Limited | Information & communication | 2009 |
| Jelly & Co (London) Ltd | Other services | 2025 |
| JEM Estates Limited | Real estate | 2002 |
| Jemoes Ltd | Health & social care | 2022 |
| Jemson Ltd | Real estate | 2017 |
| Jemstone Medical Services Ltd | Health & social care | 2026 |
| Jenez Limited | Health & social care | 2023 |
| Jenkins Farm Limited | Construction | 2014 |
| Jenny 4 Real Limited | Health & social care | 2018 |
| Jensenbowman Ltd | Manufacturing | 2018 |
| Jensons Hair and Beauty Ltd | Other services | 2022 |
| Jenyab Ltd | Health & social care | 2022 |
| Jenyauto Limited | Construction | 2017 |
| Jessica Fast Food Limited | Hospitality | 2019 |
| Jessyesthy Healthcare International Limited | Health & social care | 2023 |
| Jethro Retail Ltd | Wholesale & retail | 2022 |
| Jetty Court RTM Company Ltd | Households | 2016 |
| Jewel Property Maintenance Limited | Construction | 1999 |
| Jewel Property Services Limited | Construction | 1999 |
| JFD Real Estate Ltd | Real estate | 2025 |
| Jfjs Services Limited | Professional & scientific | 2025 |
| JG & LS Properties Ltd | Real estate | 2025 |
| Jgso Properties Ltd | Real estate | 2021 |
| JH Access Ltd | Manufacturing | 2022 |
| JH Footballing Ltd | Education | 2022 |
| Jharris Trades Ltd | Wholesale & retail | 2025 |
| JHL Films Ltd | Information & communication | 2025 |
| Jhudson Properties Ltd | Real estate | 2025 |
| JIA Mart Ltd | Wholesale & retail | 2025 |
| Jibsmedical Limited | Health & social care | 2025 |
| Jida Property Management Limited | Real estate | 2024 |
| Jidek Limited | Health & social care | 2023 |
| Jidmel Electrical Services Ltd | Construction | 2018 |
| Jilfson Services Ltd | Health & social care | 2021 |
| Jimmie Martin Design Ltd | Arts & recreation | 2020 |
| Jine Properties Limited | Real estate | 2025 |
| Jiovad Consults Ltd | Professional & scientific | 2024 |
| Jireh Medicals Limited | Health & social care | 2023 |
| JIU YU Ltd | Real estate | 2022 |
| Jive Healthcare and Staffing Ltd | Information & communication | 2024 |
| Jizz Consults Ltd | Health & social care | 2023 |
| JJB Corporation UK Limited | Manufacturing | 2016 |
| JJB Holdings U.K. Ltd | Real estate | 2022 |
| JJB Industries UK Ltd | Manufacturing | 2026 |
| JJG Portfolio Ltd | Real estate | 2023 |
| JJS & Sons Plastering Ltd | Construction | 2022 |