| J N Properties (SW) Limited | Real estate | 2016 |
| J Partridge Ltd. | Arts & recreation | 2013 |
| J Rawlingson Tattooing Ltd | Other services | 2017 |
| J Scadding & SON Property Limited | Financial services | 1911 |
| J Two Studio Ltd | Professional & scientific | 2026 |
| J Type Ltd | Professional & scientific | 2018 |
| J W Bathroom Solutions Limited | Construction | 2017 |
| J W Services Western Limited | Hospitality | 2001 |
| J&Jtradegroup Limited | Wholesale & retail | 2025 |
| J. Reynolds (Western) Limited | Construction | 1985 |
| J.A Wright's Builders Limited | Construction | 2016 |
| J.A. Heating Services Limited | Construction | 2005 |
| J.A.O Property Development Ltd | Construction | 2025 |
| J.P. Services (South West) Limited | Construction | 1995 |
| Jaba Architect Limited | Professional & scientific | 2003 |
| Jabber Digital Media Ltd | Information & communication | 2016 |
| Jack and Bean Limited | Hospitality | 2018 |
| Jack Beauty Ltd | Wholesale & retail | 2018 |
| Jack Hardy Productions Limited | Information & communication | 2014 |
| Jack Tobin Ltd | Professional & scientific | 2018 |
| Jack's World of Wine Limited | Hospitality | 2017 |
| Jackal Brands Limited | Wholesale & retail | 2012 |
| Jackson Technology Solutions Limited | Information & communication | 2023 |
| Jacob Rose Recruitment Limited | Administrative & support | 2021 |
| Jacob's Coffee House Limited | Hospitality | 2010 |
| Jacqmar Limited | Manufacturing | 2013 |
| Jacqueline Colley Ltd | Arts & recreation | 2023 |
| Jade EP Limited | Professional & scientific | 2023 |
| Jaden Kevin Ltd | Administrative & support | 2018 |
| Jaffa Dog Ltd | Professional & scientific | 2023 |
| JAG (Bath) Limited | Construction | 2009 |
| Jaggery Foods Ltd | Hospitality | 2026 |
| Jagram Limited | Manufacturing | 2005 |
| Jaiden Savery Carpentry Ltd | Construction | 2025 |
| Jaim Limited | Wholesale & retail | 2024 |
| JAK Homes Ltd | Real estate | 2019 |
| Jalumi Limited | Wholesale & retail | 2022 |
| JAM Digital Limited | Information & communication | 2024 |
| JAM Today and Tomorrow Limited | Financial services | 2026 |
| James Alexander Investment Partners Ltd | Financial services | 2020 |
| James Cheadle Media Limited | Information & communication | 2019 |
| James Gray Strategic Ltd | Professional & scientific | 2024 |
| James Grayley Architects Ltd | Professional & scientific | 2013 |
| James Lancett Illustration & Animation Ltd | Information & communication | 2013 |
| James Pembroke Holdings Limited | Financial services | 2001 |
| James Pembroke Media Limited | Information & communication | 2012 |
| James R. Pearce Developments Limited | Construction | 1999 |
| James Turner Coaching Ltd | Other services | 2026 |
| James Walsh Studio Limited | Professional & scientific | 2025 |
| Jamkam Ltd | Hospitality | 2016 |
| Jamn Design Ltd | Real estate | 2023 |
| Jams Property Ltd | Real estate | 2022 |
| Jane Austen London Ltd | Arts & recreation | 2025 |
| Jane Austen Ltd | Arts & recreation | 1998 |
| Jane Knapp Ltd | Wholesale & retail | 2002 |
| Jane Toplis Associates Ltd | Professional & scientific | 2010 |
| Jane Williams Consulting Limited | Information & communication | 2004 |
| Janire Limited | Real estate | 2002 |
| Janus Mediation Services Ltd | Professional & scientific | 2019 |
| Japan Business Consultancy Limited | Professional & scientific | 1991 |
| Jarelko Limited | Information & communication | 2014 |
| JAS Lall Limited | Professional & scientific | 2018 |
| Jatc Consulting Limited | Professional & scientific | 2017 |
| Javo Comms Ltd | Administrative & support | 2018 |
| Jawz Limited | Information & communication | 2015 |
| JAY Ranks Ltd | Information & communication | 2026 |
| Jaycorp Ltd | Professional & scientific | 2025 |
| Jays Driving School Company Limited | Education | 2025 |
| Jazoh Properties Limited | Real estate | 2022 |
| JB Cosmetic Dentures Ltd | Health & social care | 2011 |
| JB Orthopaedics Ltd | Health & social care | 2019 |
| Jbab Ltd | Financial services | 2025 |
| JBD Recruitment Limited | Administrative & support | 2014 |
| Jbux Limited | Information & communication | 2015 |
| JC 16 Limited | Arts & recreation | 2017 |
| JC Digital Ltd | Information & communication | 2024 |
| JC Distributionuk Ltd | Wholesale & retail | 2023 |
| Jcap Holdings Limited | Real estate | 2025 |
| Jcbit Limited | Information & communication | 2012 |
| JCE Contracting Limited | Construction | 2002 |
| JCE Investments Limited | Real estate | 2014 |
| Jconstruct Bath Ltd | Manufacturing | 2025 |
| JD Building (Maintenance) Ltd | Construction | 2021 |
| JD Building (Refurbishment) Limited | Construction | 2012 |
| Jdethierry Ltd | Arts & recreation | 2023 |
| JEB Holdings Limited | Financial services | 2023 |
| Jelinek Cork Limited | Manufacturing | 2008 |
| Jellicoe M&A Limited | Professional & scientific | 2023 |
| Jellysonic Limited | Wholesale & retail | 2017 |
| Jemma Business Associates Ltd | Professional & scientific | 2016 |
| Jenerus Limited | Information & communication | 2005 |
| Jenkins Developments Limited | Construction | 1984 |
| Jennifer Mosse Design Ltd | Professional & scientific | 2019 |
| Jennings Legal Services Limited | Professional & scientific | 2001 |
| Jenny Cowderoy Limited | Professional & scientific | 2015 |
| Jentico Ltd | Information & communication | 2024 |
| Jeremy Guscott Limited | Real estate | 1998 |
| Jeremy Yates Limited | Wholesale & retail | 2017 |
| Jeremylabram.Com Limited | Professional & scientific | 2013 |
| Jerime Attah FP Ltd | Other services | 2021 |