| James Stewart Ltd | Construction | 2015 |
| Jamesbrandux Ltd | Information & communication | 2019 |
| Jamin Paws Enterprises Ltd | Wholesale & retail | 2024 |
| Jams Property Management Ltd | Real estate | 2018 |
| Jams Trading Limited | Wholesale & retail | 2017 |
| Jande Capital Limited | Professional & scientific | 2016 |
| Jane IT Systems Limited | Information & communication | 2000 |
| Janiola Properties Ltd | Hospitality | 2025 |
| Janlee Investment Limited | Financial services | 1985 |
| Janper Properties Ltd | Real estate | 2018 |
| Jantunari Ltd | Transport & logistics | 2016 |
| Japji Ltd | Transport & logistics | 2026 |
| Japz IT Ltd | Information & communication | 2018 |
| Japz Property & Lettings Ltd | Real estate | 2020 |
| Jarrovian Group Ltd | Professional & scientific | 2017 |
| Jarrovian Trust and Estate Services Limited | Financial services | 2016 |
| Jarrovian Wealth Limited | Financial services | 2016 |
| Jarvis Carpentry and Joinery Ltd | Manufacturing | 2005 |
| Jarvis Developers Limited | Construction | 2013 |
| Jarvis Group Holdings Limited | Financial services | 2020 |
| Jarvis Venture Ltd | Wholesale & retail | 2024 |
| JARVIS607 Limited | Information & communication | 2010 |
| Jasad Private Limited | Health & social care | 2019 |
| Jasdil Beauty Ltd | Other services | 2016 |
| Jash for Ever Ltd | Information & communication | 2014 |
| Jasmine Property Investment Ltd | Real estate | 2024 |
| Jasmine Services Limited | Administrative & support | 2019 |
| Jasmineae Ltd | Other services | 2024 |
| Jason Properties Ltd | Real estate | 2025 |
| Jasper & George Dog Concierge Ltd | Other services | 2026 |
| Jasper Consultants Limited | Other services | 2017 |
| JAX Financial Services Limited | Financial services | 2024 |
| JAY Glennie Limited | Arts & recreation | 2013 |
| JAY Phillips Ltd | Professional & scientific | 2024 |
| Jayanthi & Co Limited | Health & social care | 2011 |
| Jaydee Care Ltd | Administrative & support | 2025 |
| Jaylance Limited | Professional & scientific | 2001 |
| Jayne's Nursery Ltd | Health & social care | 2013 |
| Jays Mechanical Services Limited | Construction | 2022 |
| Jayserv Limited | Manufacturing | 2012 |
| Jaytrade (UK) Limited | Wholesale & retail | 2006 |
| JB Bracknell Limited | Hospitality | 2025 |
| JB Fitness Ltd | Arts & recreation | 2021 |
| JBD Investments Limited | Financial services | 2019 |
| Jbdworld Ltd | Professional & scientific | 2025 |
| JBH Landscapes Ltd | Administrative & support | 2023 |
| JBJ Limited | Hospitality | 2025 |
| JBS Tyres Limited | Wholesale & retail | 2012 |
| JBW Essex Ltd | Financial services | 2024 |
| JC (U.K.) Limited | Real estate | 2023 |
| JC Analytics & AI Ltd | Information & communication | 2025 |
| JC Exclusive Ltd | Real estate | 2025 |
| JC Flooring (Essex) Ltd | Construction | 2026 |
| JC Interiors Fitouts Limited | Construction | 2014 |
| JC Interiors Limited | Construction | 2012 |
| JCD Cares and Resources Limited | Administrative & support | 2020 |
| JCD SPV I Ltd | Construction | 2025 |
| JCE Accountants Limited | Professional & scientific | 2021 |
| Jcjh Limited | Professional & scientific | 2017 |
| Jcma Group Ltd | Information & communication | 2025 |
| JCN Property Limited | Financial services | 2026 |
| JCS Building Developments Limited | Construction | 2017 |
| Jcube Consultancy Private Limited | Information & communication | 2017 |
| JD Craft Ltd | Wholesale & retail | 2021 |
| JD Hynard Properties Limited | Real estate | 2025 |
| JD Psychological Service Ltd | Education | 2023 |
| Jdconsulting Ltd | Professional & scientific | 2024 |
| Jdgt Ltd | Information & communication | 2025 |
| JDL UK Holdings Ltd | Financial services | 2023 |
| JDM Pulse Ltd | Wholesale & retail | 2025 |
| JDR Financial Solutions Limited | Extraterritorial | 2007 |
| JE Care & Consultants Ltd | Health & social care | 2019 |
| Jean Merchant Holdings Limited | Professional & scientific | 2007 |
| Jeba Consulting Limited | Information & communication | 2015 |
| Jeco Group Limited | Financial services | 2026 |
| JEE & JU Ltd | Wholesale & retail | 2018 |
| JEE Associates Limited | Professional & scientific | 2003 |
| Jeev Properties Limited | Real estate | 2023 |
| Jeeves Car Valeting Ltd | Wholesale & retail | 2018 |
| Jeffy Jeffy Limited | Health & social care | 2025 |
| Jeje Consulting Limited | Professional & scientific | 2021 |
| Jeko Investments Limited | Real estate | 2022 |
| Jellmac Solutions Limited | Professional & scientific | 2009 |
| Jemma Skidmore Music Services Limited | Other services | 2012 |
| Jennings Engineering Supplies Partnership LP | | 2001 |
| Jenny Epps Limited | Transport & logistics | 2016 |
| Jenny Moody Properties Limited | Construction | 1985 |
| Jerk Station Ltd | Manufacturing | 2019 |
| Jermyn Street Holdings Ltd | Professional & scientific | 2025 |
| Jerry Management Services Ltd | Administrative & support | 2023 |
| Jesmond Productions Limited | Information & communication | 1998 |
| Jess Design Consultants Ltd | Professional & scientific | 2018 |
| Jess Lelliott Ltd | Professional & scientific | 2025 |
| Jess Property Limited | Real estate | 2015 |
| Jessica Gardiner Ltd | Other services | 2008 |
| Jessica Perry Ltd | Wholesale & retail | 2026 |
| Jessie Rose Investments Limited | Extraterritorial | 2014 |
| Jessop Holdings Limited | Agriculture & fishing | 1947 |
| JET Stream Lifestyle Ltd | Administrative & support | 2019 |
| Jetbytes Solutions Ltd | Information & communication | 2024 |