| J.J.P.J.C. Limited | Professional & scientific | 2000 |
| Jack & Freda Ltd | Wholesale & retail | 2019 |
| Jackson California HUT Ltd | Hospitality | 2025 |
| Jackson California Lake Ltd | Hospitality | 2019 |
| Jade Security Services Limited | Administrative & support | 1998 |
| JAG UK Bidco Limited | Financial services | 2019 |
| JAG UK Holdco Limited | Financial services | 2019 |
| JAG UK Midco Limited | Financial services | 2019 |
| JAG UK Topco Limited | Financial services | 2019 |
| JAM & Bone Media Ltd | Professional & scientific | 2018 |
| JAM Infotech Limited | Information & communication | 2016 |
| James Johnston Heating Ltd | Construction | 2025 |
| James Kirk Design Limited | Arts & recreation | 2008 |
| Jamies Real Estate Limited | Real estate | 2025 |
| Jamogen Capital Limited | Real estate | 2019 |
| Jamoo Limited | Professional & scientific | 2005 |
| Janes Accounting Services Limited | Professional & scientific | 2020 |
| Jaque-Michelson Ltd | Professional & scientific | 2010 |
| JAR Energy Ltd | Professional & scientific | 2020 |
| Jardin D' Eden Ltd | Other services | 2017 |
| Java Cafe Ltd | Hospitality | 2018 |
| Javari Jealouse Ltd | Extraterritorial | 2022 |
| Javelin Consult Limited | Professional & scientific | 2024 |
| Jawad Properties Ltd | Real estate | 2020 |
| JAY Printers Limited | Manufacturing | 2003 |
| Jayem Ltd | Information & communication | 2023 |
| JB Euro Media Ltd | Information & communication | 2025 |
| JB Export Services Ltd | Wholesale & retail | 2018 |
| JB Group Services Ltd | Administrative & support | 2022 |
| JB Peterborough Limited | Hospitality | 2026 |
| Jbarton Consulting Ltd | Information & communication | 2025 |
| Jbmask Ltd | Information & communication | 2019 |
| Jbtripreports Ltd | Information & communication | 2021 |
| JC Barker Investments Ltd | Information & communication | 2026 |
| JC Roofing and Property Services Ltd | Construction | 2025 |
| JC Urban Planning Ltd | Professional & scientific | 2024 |
| Jcurv Limited | Professional & scientific | 2015 |
| JD Casa Developments Limited | Construction | 2026 |
| JD Motors Ltd | Wholesale & retail | 2017 |
| Jdeazle Ltd | Professional & scientific | 2014 |
| JDH Mechanical Services Ltd | Construction | 2013 |
| JDH Solutions Limited | Administrative & support | 2005 |
| JDP Consulting Services Ltd | Professional & scientific | 2024 |
| JDS Energy Services Ltd | Construction | 2021 |
| Jeax Limited | Information & communication | 2017 |
| Jeff Chuter Ltd | Financial services | 2016 |
| Jeffers Property Limited | Real estate | 2024 |
| Jemini Flowers Oxford Ltd | Wholesale & retail | 2019 |
| Jenahura Limited | Professional & scientific | 2005 |
| Jenerosity Limited | Financial services | 2023 |
| Jennings Pubs Ltd | Hospitality | 2023 |
| Jetarch Design Ltd. | Professional & scientific | 2013 |
| JGK Hire Limited | Wholesale & retail | 2013 |
| JGS Services Limited | Construction | 2018 |
| JH Fabrications Ltd | Construction | 2022 |
| JHA Holdings Ltd | Financial services | 2026 |
| JIA Cheng Trading Ltd | Health & social care | 2006 |
| Jiadeng Limited | Other services | 2025 |
| JIL Properties Ltd | Real estate | 2021 |
| Jilluminate Limited | Information & communication | 2010 |
| Jimak Ltd | Wholesale & retail | 2025 |
| Jivyah Limited | Financial services | 2023 |
| JJ Capital Ltd | Real estate | 2024 |
| JJB Building Foundation Ltd | Construction | 2016 |
| Jjrm Services Ltd | Professional & scientific | 2017 |
| JK 79 Limited | Professional & scientific | 2025 |
| JK Home Group Ltd | Real estate | 2021 |
| Jkaproperty Limited | Real estate | 2020 |
| Jkrwan Consulting Service Ltd | Other services | 2013 |
| JLR Roofing Solutions Ltd | Construction | 2023 |
| JLS Business Consultancy Ltd | Professional & scientific | 2018 |
| Jlux Electrical Ltd | Construction | 2025 |
| JM Design Consultants Limited | Wholesale & retail | 2015 |
| JM Global Services Limited | Information & communication | 2015 |
| Jmks Services Ltd | Professional & scientific | 2025 |
| JMW Business Consulting Ltd | Professional & scientific | 2019 |
| Jnnovate Limited | Information & communication | 2015 |
| Jodair Management Services Limited | Manufacturing | 1993 |
| Joes Property Development Ltd | Construction | 2025 |
| Joesbury Ltd | Professional & scientific | 2022 |
| Joesgarden Ltd | Wholesale & retail | 2024 |
| Johannes Court Property Management Company Limited | Households | 1969 |
| Johe Developments LLP | | 2020 |
| John Ariss Property Holdings Ltd | Real estate | 2021 |
| John O'Gaunt Inn Ltd | Hospitality | 2025 |
| John Wenman Ecological Consultancy LLP | | 2008 |
| Johnson & Johnson Finance Limited | Administrative & support | 1973 |
| Johnson & Johnson Management Limited | Administrative & support | 1925 |
| Johnson & Johnson UK Treasury Company Limited | Financial services | 2015 |
| Johnson Rodriguez Consulting Limited | Information & communication | 2014 |
| Joincoachly Ltd | Arts & recreation | 2026 |
| JOJ Inc Consultancy Ltd | Professional & scientific | 2018 |
| JOJ Property Service Ltd | Real estate | 2021 |
| JON Bradley Photography Limited | Professional & scientific | 2003 |
| Jonny's Drains (Berkshire) Ltd | Construction | 2024 |
| Jonrog Limited | Health & social care | 2019 |
| Joshua Scott Ltd | Professional & scientific | 2023 |
| Journey Recruitment Ltd | Administrative & support | 2014 |
| Joy Cafe Wokingham Ltd | Hospitality | 2024 |
| JP Cooper Limited | Arts & recreation | 2019 |