| JJZ Quality Solutions Ltd | Construction | 2026 |
| Jkcdirect Ltd | Transport & logistics | 2025 |
| JKS Property Solutions Ltd | Construction | 2024 |
| JM Advisors Limited | Information & communication | 2024 |
| JMG ED Tech Consulting Limited | Professional & scientific | 2014 |
| JMO Property Services Limited | Real estate | 2013 |
| JOE Homes Ltd | Real estate | 2019 |
| Johan Private Limited | Real estate | 2026 |
| John Barmby Limited | Professional & scientific | 2012 |
| John Brayford Laundry Consultancy Ltd | Professional & scientific | 2017 |
| John Darby Auto Repairs Limited | Wholesale & retail | 2006 |
| John Dovey Wills & Probate Limited | Professional & scientific | 2021 |
| John K.Daly & Co. Limited | Professional & scientific | 2004 |
| John Nicholls (Holdings) Limited | Professional & scientific | 2003 |
| John Nicholls (Trading) Limited | Wholesale & retail | 1965 |
| John Nicholls Management Limited | Wholesale & retail | 2022 |
| John Nicholls Racing LLP | | 2020 |
| John Tibbetts (Europarts) Limited | Extraterritorial | 1986 |
| Johnson Ribolla Limited | Professional & scientific | 2014 |
| Joines & Sons Transport Limited | Transport & logistics | 2006 |
| Jojo Mobiles Ltd | Wholesale & retail | 2020 |
| Joma Jewellery Ltd | Wholesale & retail | 2011 |
| Jones Robinson (Didcot) Limited | Real estate | 2005 |
| Jones Robinson Estate Agents Holdings Limited | Real estate | 2014 |
| Jones Robinson Estate Agents Limited | Real estate | 1998 |
| Jont Products and Services Ltd | Construction | 2021 |
| Jonya Limited | Information & communication | 2020 |
| Jooca Ltd | Information & communication | 2022 |
| Jovial Frose Limited | Information & communication | 2018 |
| Joys of Maintenance Ltd | Construction | 2021 |
| JP Cleaning & Property Services Ltd | Construction | 2016 |
| Jpetulia Ltd | Transport & logistics | 2020 |
| Jpmc Surveying Ltd | Professional & scientific | 2025 |
| JR Pre-Training & Breaking Ltd | Arts & recreation | 2023 |
| JRB Digital Ltd | Information & communication | 2014 |
| JRD Trading Ltd | Wholesale & retail | 2026 |
| Jrst Property Limited | Real estate | 2015 |
| JS Accountancy Services (Oxford) Limited | Professional & scientific | 2021 |
| JS Memories Ltd | Information & communication | 2025 |
| JSC Media Ltd | Information & communication | 2016 |
| JSD (Banbury) Ltd | Real estate | 2023 |
| Jsdarby Holdings Ltd | Real estate | 2022 |
| JSP Management Ltd | Administrative & support | 2007 |
| Jsrp Holdings Limited | Financial services | 2022 |
| Jstkb Properties Ltd | Real estate | 2024 |
| JTA Interiors Limited | Construction | 2013 |
| JTD Project Management Services Limited | Construction | 2020 |
| Jtmunii Limited | Transport & logistics | 2025 |
| JU Property Solutions Ltd | Real estate | 2016 |
| Judith F Miller Limited | Health & social care | 2010 |
| Juice Global Holdings Limited | Financial services | 2022 |
| Juice Global Limited | Wholesale & retail | 2012 |
| Jujhar Transport U.K. Ltd | Transport & logistics | 2025 |
| Julia Gordon Floral Studio Limited | Wholesale & retail | 2021 |
| Julie Mclean Ltd | Administrative & support | 2011 |
| Julies's Hairdressing (UK) Limited | Other services | 2026 |
| Junior Groovers Ltd | Education | 2025 |
| Juno Estates Limited | Real estate | 1999 |
| Jupiter Edtech Limited | Administrative & support | 2024 |
| Just the One PUB Actually Limited | Hospitality | 2021 |
| Justin Bucknell Electrical Limited | Construction | 2015 |
| Juvenis.London Ltd | Health & social care | 2016 |
| JW Hair & Beauty Ltd | Other services | 2025 |
| JWB Farming Limited | Agriculture & fishing | 2012 |
| JWP Delivery Ltd | Transport & logistics | 2020 |
| JWW Associates Limited | Professional & scientific | 2013 |
| Jwwr Ltd | Real estate | 2025 |
| JXR Technology Limited | Wholesale & retail | 2025 |
| K & D Technical Services Ltd | Professional & scientific | 2018 |
| K & G Cleaning Limited | Administrative & support | 2024 |
| K & T Magic Home Ltd | Administrative & support | 2024 |
| K H Holiday Homes (Somerset) Limited | Hospitality | 2023 |
| K H Holiday Homes Limited | Hospitality | 2021 |
| K Sharma Property Ltd | Real estate | 2024 |
| K Sutton Garage Ltd | Wholesale & retail | 2019 |
| K&S Wholesale Limited | Wholesale & retail | 2025 |
| K. J. Brookes Builders Limited | Construction | 2005 |
| K.J. Cherry & Sons Limited | Agriculture & fishing | 1963 |
| K4 Healthcare Services Limited | Health & social care | 2024 |
| K7 Wfsc UK Ltd | Real estate | 2022 |
| Kaafi LUX Ltd | Administrative & support | 2025 |
| Kabnab Consult Ltd | Other services | 2022 |
| Kacao Ltd | Hospitality | 2025 |
| Kaia B Ltd | Real estate | 2026 |
| Kaina Universe Limited | Wholesale & retail | 2025 |
| Kairuien Ltd | Wholesale & retail | 2024 |
| Kaku Healthcare Services Ltd | Health & social care | 2023 |
| Kaleidoscope Homes Limited | Construction | 2017 |
| Kamboh Gateway Limited | Wholesale & retail | 2025 |
| Kan's Kitchen Ltd | Hospitality | 2021 |
| Kanady Limited | Wholesale & retail | 2002 |
| Kangaroo Music Limited | Arts & recreation | 1970 |
| Kannegiesser UK Limited | Manufacturing | 1978 |
| Karcher (U.K.) Limited | Wholesale & retail | 1978 |
| Karcher Hire Limited | Administrative & support | 2008 |
| Karen Haller Interiors Limited | Professional & scientific | 2007 |
| Karlmt Ltd | Transport & logistics | 2026 |
| Karmilla Ltd. | Information & communication | 2005 |
| Kasa AI Labs Ltd | Professional & scientific | 2026 |
| Kate Barlow: Branching OUT Ltd | Administrative & support | 1999 |