| Jarvis Plumbing & Heating Ltd | Construction | 2015 |
| Jason Morris Ltd | Professional & scientific | 2019 |
| Javelin Coaching Ltd | Administrative & support | 2014 |
| JAY Dacey Limited | Administrative & support | 2010 |
| JB Audio Post Production Ltd | Information & communication | 2019 |
| JB DIY Services Ltd | Construction | 2023 |
| JBK3 Limited | Arts & recreation | 2015 |
| JDG Waterhouse Limited | Professional & scientific | 2014 |
| JDM Life Sciences Limited | Professional & scientific | 2018 |
| JDS Electrical Solutions Limited | Construction | 2012 |
| JEB PMC Limited | Extraterritorial | 2015 |
| Jelly Drops (U.K.) Ltd | Manufacturing | 2021 |
| Jelly Drops Ltd | Manufacturing | 2018 |
| Jemma Luxe Ltd | Financial services | 2018 |
| Jenkins Brothers (Essex) Limited | Agriculture & fishing | 1995 |
| Jenny Law Design Ltd | Professional & scientific | 2017 |
| Jessica Hammett Limited | Arts & recreation | 2022 |
| JET Black Estates Limited | Construction | 2015 |
| JET Developers Ltd | Construction | 2018 |
| Jetec Electrical Contractors Limited | Construction | 2011 |
| JF Ltd | Extraterritorial | 2009 |
| JG Ltd | Extraterritorial | 2009 |
| Jhcj Services Ltd | Construction | 2024 |
| Jiminy Snippets Ltd | Other services | 2011 |
| Jimmy Tilley Creative Ltd | Professional & scientific | 2021 |
| JJ Alexander Limited | Real estate | 2025 |
| JJG Consulting Ltd | Professional & scientific | 2022 |
| JJS Creative Collective Ltd | Arts & recreation | 2024 |
| JL Property Projects Limited | Construction | 2026 |
| JL Rushton Ltd | Health & social care | 2010 |
| JLA Landscape & Gardening Ltd | Administrative & support | 2024 |
| JMB Agencies (UK) Limited | Professional & scientific | 1987 |
| Jmcl Legals Ltd | Administrative & support | 2026 |
| JMH Capital Limited | Professional & scientific | 2026 |
| JMJ Construction Limited | Construction | 2017 |
| Joanna Eden Outreach C.I.C. | Education | 2017 |
| Joanna Hughes Limited | Professional & scientific | 2022 |
| Joanna Services Ltd | Administrative & support | 2017 |
| John Hicks Co Limited | Professional & scientific | 2012 |
| John Miles & SON Tyre & Exhaust Centre Limited | Wholesale & retail | 2003 |
| John Patrick Development & Design Limited | Construction | 2003 |
| John Raisin Financial Services Limited | Financial services | 2009 |
| Johns Farm Management Company Limited | Extraterritorial | 1989 |
| Johnston Trevail Limited | Professional & scientific | 2022 |
| Joinery by Design Limited | Manufacturing | 1993 |
| Jojo's Mojo Limited | Information & communication | 2012 |
| Jonathan Wood Vintage & Thoroughbred Restorations Limited | Manufacturing | 2011 |
| Jones and Partridge Investments Ltd | Wholesale & retail | 2025 |
| Joseph Fordham & Sons Limited | Agriculture & fishing | 1958 |
| Joseph Pastures Ltd | Construction | 2020 |
| Joyce Design UK Limited | Professional & scientific | 2009 |
| JP Brew Limited | Manufacturing | 2017 |
| JP Taylor Engineering Ltd | Professional & scientific | 2021 |
| JPH and SON Limited | Construction | 2023 |
| Jppg Limited | Health & social care | 2023 |
| JPS Trade Limited | Administrative & support | 2019 |
| JRB Builds Ltd | Construction | 2019 |
| Jrgw Limited | Agriculture & fishing | 2026 |
| JRH Agronomy Ltd | Professional & scientific | 2022 |
| JS Walden Consultancy Limited | Professional & scientific | 2020 |
| JT Electrical (Enfield) Ltd | Manufacturing | 2015 |
| JTE Electrical Ltd | Manufacturing | 2024 |
| JTM Partners LLP | | 2026 |
| Jubilee Resource Community Ltd | Construction | 2014 |
| Judicious Supporting Services (JSS) | Education | 2023 |
| Julian Shoolheifer Limited | Wholesale & retail | 2005 |
| Junction 9 Network Ltd | Information & communication | 2012 |
| Junction 9 Property Ltd | Real estate | 2015 |
| Jupiter Telcom Ltd | Wholesale & retail | 2016 |
| Justplay Saffron Walden Limited | Hospitality | 2022 |
| K L Cowan Limited | Construction | 2025 |
| K.Beeson Plumbing and Heating Ltd | Construction | 2018 |
| K2 Data Limited | Information & communication | 2020 |
| K2 Property Partners Limited | Real estate | 2025 |
| Kahina Consulting Limited | Information & communication | 2023 |
| Kalkine Limited | Information & communication | 2012 |
| Kalkine Media Ltd | Professional & scientific | 2020 |
| Kamal DC Ltd. | Hospitality | 2020 |
| Kanso Design Ltd | Professional & scientific | 2019 |
| Karori Management Services Limited | Professional & scientific | 2019 |
| Kastwork Limited | Administrative & support | 2004 |
| Katie Malik Studio Ltd. | Professional & scientific | 2019 |
| Kavita Collective Ltd | Wholesale & retail | 2025 |
| KAY Pilsbury Thomas Architects Limited | Professional & scientific | 2004 |
| Kaylem Limited | Real estate | 2007 |
| KB Cargo Limited | Professional & scientific | 2025 |
| KB Health Practitioner Ltd | Health & social care | 2018 |
| KB PMC Limited | Extraterritorial | 2016 |
| Kdllf Limited | Information & communication | 2018 |
| Kegworth Solar LLP | | 2015 |
| Keiracraft Ltd | Construction | 2025 |
| Keith Porter Communications Limited | Administrative & support | 2021 |
| Keldea Management Limited | Professional & scientific | 2006 |
| Kemo Properties Ltd | Households | 2025 |
| Kenneth Consulting Ltd | Information & communication | 2013 |
| Kensington Press Limited | Education | 1998 |
| Kent Sabah Ltd | Real estate | 2023 |
| Kentish MAN Holdings Limited | Financial services | 2020 |
| Kenzie Contracts Ltd | Administrative & support | 2011 |
| Kerron Consulting Ltd. | Other services | 2019 |