| Jane Castree and ... CIC | Arts & recreation | 2026 |
| Jarod John Ltd | Wholesale & retail | 2021 |
| Jason Gillett Groundworks Limited | Construction | 2012 |
| Jason Maguire Limited | Arts & recreation | 2005 |
| Jason Watson Racing Limited | Arts & recreation | 2018 |
| Java KMK Ltd | Hospitality | 2025 |
| JBF Plumbing & Heating Ltd | Construction | 2016 |
| JDB Sports Ltd | Wholesale & retail | 2025 |
| Jefferis & Boyd Ltd | Professional & scientific | 2025 |
| Jegal Creation Limited | Wholesale & retail | 2025 |
| Jemcas Limited | Other services | 2016 |
| Jennings Carpentry & Construction Ltd | Construction | 2020 |
| Jequier Newitt Insurance Brokers Limited | Financial services | 2002 |
| Jessica's Beauty Bar Ltd | Other services | 2025 |
| Jethold (UK) Ltd | Real estate | 2024 |
| Jetin Ltd | Wholesale & retail | 2025 |
| Jewelry Focus Ltd | Wholesale & retail | 2016 |
| JF Accountancy Ltd | Professional & scientific | 2024 |
| JFH Solutions Limited | Construction | 2020 |
| JFR Studio Limited | Information & communication | 2015 |
| JG Audio Ltd | Arts & recreation | 2026 |
| Jgpfabrication Limited | Manufacturing | 2023 |
| Jilt Ltd | Health & social care | 2022 |
| JIM Crowley Ltd | Arts & recreation | 2006 |
| JIM Davies Consulting Limited | Other services | 2018 |
| Jireh Homes Support Ltd | Real estate | 2023 |
| JJC Homes Ltd | Construction | 2024 |
| Jjjb Ltd | Administrative & support | 2014 |
| JJO Properties Limited | Real estate | 2019 |
| JJT Cooperation Limited | Financial services | 2025 |
| JJT Smile Cooperation Limited | Health & social care | 2025 |
| JK Bites Ltd | Hospitality | 2023 |
| JKC Investments Ltd | Real estate | 2017 |
| JM2 Courses Ltd | Education | 2024 |
| JM2 Music Ltd | Arts & recreation | 2022 |
| JMA Homes Limited | Real estate | 2016 |
| JMB Advisory Ltd | Other services | 2025 |
| JME Partners Ltd | Professional & scientific | 2017 |
| Jmottylogistics Ltd | Transport & logistics | 2026 |
| JNM Display Limited | Professional & scientific | 2019 |
| JNS Advisory Limited | Public administration | 2023 |
| Joanna Elizabeth Osipczak Limited | Extraterritorial | 2025 |
| Joanna G Consultancy Limited | Professional & scientific | 2014 |
| Joeburbankprimarymathsconsultancy Ltd | Education | 2019 |
| John Abbey Representation Ltd | Arts & recreation | 2023 |
| John Allan Travel Limited | Administrative & support | 2014 |
| John Barker (Consulting) Limited | Professional & scientific | 2004 |
| John E Hughes Ltd | Financial services | 2025 |
| John Linton Property Limited | Real estate | 2019 |
| Johnsons Site Management Ltd | Construction | 2025 |
| Jonathan Burke Racing Limited | Arts & recreation | 2019 |
| Jones Orthodontics Limited | Health & social care | 2022 |
| Jonesthefone Consulting Limited | Information & communication | 2009 |
| Jonjo O’Neill JR Ltd | Arts & recreation | 2019 |
| Jopaul Consulting Ltd | Professional & scientific | 2026 |
| Joyce Authentic Care Ltd | Public administration | 2024 |
| JPP Knight Consulting Ltd | Professional & scientific | 2020 |
| JR Shipping Limited | Wholesale & retail | 2018 |
| JRB Publishing Services Ltd | Information & communication | 2014 |
| JRP Civils Limited | Construction | 2007 |
| JSC Solutions Ltd | Information & communication | 2003 |
| Jthr Group Ltd | Real estate | 2025 |
| JTW Media Ltd | Professional & scientific | 2011 |
| Juan Cogollos Ltd | Education | 2020 |
| Julie Sargent Education Consultancy Ltd | Education | 2016 |
| JUN Wang UK Limited | Other services | 2017 |
| Junk Serpent Productions Ltd | Information & communication | 2022 |
| Just Good Sense Limited | Information & communication | 2020 |
| JV Building Services 1 Limited | Construction | 2023 |
| JW86 Limited | Real estate | 2019 |
| JY Renewables Ltd | Construction | 2025 |
| K and F Brickwork and Construction Ltd | Administrative & support | 2019 |
| K J Building Developments Ltd | Construction | 2024 |
| K&Da Building Limited | Construction | 2026 |
| Kabru Business Solutions Limited | Professional & scientific | 2010 |
| Kainium Ltd | Professional & scientific | 2025 |
| Kairo Keyz Limited | Information & communication | 2024 |
| Kairos Networks LLP | | 2025 |
| Kajoe Limited | Real estate | 2003 |
| Kanlet Limited | Real estate | 1996 |
| Kantian Ltd | Professional & scientific | 2025 |
| Karate Academy Oxford Ltd | Education | 2026 |
| KAS Technologies Holdings Limited | Manufacturing | 2014 |
| KAT Enterprises Abingdon Ltd | Hospitality | 2024 |
| KAT Enterprises Abingdon NO2 Limited | Hospitality | 2024 |
| Katyon Limited | Wholesale & retail | 2022 |
| Kaza Property Ltd | Real estate | 2024 |
| Kb&Ag Limited | Professional & scientific | 2016 |
| KCD Renovations Ltd | Construction | 2021 |
| Kecally Limited | Construction | 2025 |
| Keele University International College Limited | Education | 2021 |
| Keen Partnership Limited | Professional & scientific | 2013 |
| Keep Couriers Limited | Transport & logistics | 2021 |
| Keith Harte Bloodstock Limited | Agriculture & fishing | 2011 |
| Kela Consulting Limited | Information & communication | 2005 |
| Kendon Capital Limited | Professional & scientific | 2013 |
| Kennington Motors Ltd | Wholesale & retail | 2019 |
| Keno Property Services Ltd | Construction | 2022 |
| Kenward Orthopaedic Limited | Manufacturing | 2000 |
| Kevin Brogan Racing Ltd | Arts & recreation | 2021 |