| John Bean Technologies Limited | Manufacturing | 2008 |
| John Bowling Ltd | Information & communication | 2023 |
| John Davis.Jc Ltd | Information & communication | 2011 |
| John Dolbear Tyre & Auto Services Limited | Wholesale & retail | 2010 |
| John Drew Transport Ltd | Transport & logistics | 2007 |
| John Dyer (Life & Pensions) Limited | Financial services | 1987 |
| John G C Ltd | Transport & logistics | 2023 |
| John Govier Glazing Ltd | Construction | 2016 |
| John Gowing Jewellers Limited | Manufacturing | 2006 |
| John Greedy Electrical Limited | Construction | 2016 |
| John Grips Limited | Information & communication | 2010 |
| John Hall & SON (Oldham) Limited | Manufacturing | 1906 |
| John Hedges Westview Developments Ltd | Construction | 2015 |
| John Henry Flowers Ltd | Wholesale & retail | 2022 |
| John Hickton & Co.,Limited | Manufacturing | 1921 |
| John Jeanes Ltd | Information & communication | 2019 |
| John Powell Properties Limited | Households | 2015 |
| John Stephenson Ltd | Information & communication | 2010 |
| John Swandells Asbestos Services Ltd | Other services | 2019 |
| John Truelove Properties Limited | Households | 2021 |
| John Williams Consulting Limited | Information & communication | 2011 |
| John Williams GAS & OIL Training/Assessing Services Ltd | Education | 2013 |
| John Winter Student Houses LLP | | 2024 |
| John Wynne Limited | Construction | 2008 |
| Johnkeans UK Ltd | Manufacturing | 2024 |
| Johns Haulage Ltd | Transport & logistics | 2019 |
| Johns Jones & LO (Client Support) Limited | Professional & scientific | 2014 |
| Johns Jones & LO Limited | Professional & scientific | 2000 |
| Johnsey Agricultural Contracting Services Ltd | Agriculture & fishing | 2024 |
| Johnson Air Conditioning Ltd | Construction | 2023 |
| Johnson's Facilities Management Ltd | Construction | 2023 |
| Johnston Enterprise Limited | Real estate | 2021 |
| Johny Building Work Ltd | Construction | 2024 |
| Joilife Ltd | Extraterritorial | 2019 |
| Join Aspen Ltd | Professional & scientific | 2023 |
| Join-Addy Ltd | Financial services | 2025 |
| Joint Inspection Team for Building Safety (Wales) Limited | Public administration | 2023 |
| Jojo and Inky's Big Adventure Ltd | Administrative & support | 2019 |
| Jojozhang Limited | Wholesale & retail | 2018 |
| Jokersson Sports & Medical Ltd | Education | 2021 |
| JOL UK Ltd | Administrative & support | 2011 |
| Jolie Ltd | Transport & logistics | 2018 |
| Jolirea Limited | Wholesale & retail | 2021 |
| Joliver Finance & Consulting Limited | Professional & scientific | 2019 |
| Jollof Box Ltd | Hospitality | 2012 |
| Jolly Tiger Limited | Real estate | 2020 |
| Jollybrothers UK Ltd | Construction | 2018 |
| Jollyjubileeonline Ltd | Wholesale & retail | 2023 |
| Jollyza Ltd | Wholesale & retail | 2025 |
| Jolyon@Thebay Limited | Hospitality | 2003 |
| Joma Healthcare Limited | Health & social care | 2024 |
| Jomo People Ltd | Administrative & support | 2018 |
| JON FOX 121 Limited | Arts & recreation | 2011 |
| JON Purnell Wealth Management Limited | Professional & scientific | 2019 |
| Jonagold Ltd | Administrative & support | 2014 |
| Jonaitis Kystfiske Limited | Extraterritorial | 2025 |
| Jonashan Ltd | Real estate | 2019 |
| Jonathan Hext Limited | Arts & recreation | 2018 |
| Jonathan Nicholls Ltd | Health & social care | 2024 |
| Jonathan Rees Quality Services Limited | Professional & scientific | 2013 |
| Jonathan Richards Financial Consultancy Ltd | Professional & scientific | 2012 |
| Jonathan Vining Limited | Extraterritorial | 2011 |
| Jonathon Bray Limited | Professional & scientific | 2011 |
| Jonathon Pugh Ltd | Health & social care | 2022 |
| Jones & Cadogan Properties Ltd | Hospitality | 2024 |
| Jones and Jones Consultancy Ltd | Education | 2018 |
| Jones and Josh Company Ltd | Administrative & support | 2022 |
| Jones Aviation Consulting Limited | Administrative & support | 2020 |
| Jones Barber Ltd | Other services | 2024 |
| Jones Brothers Demolition Limited | Construction | 2019 |
| Jones Cosy Homes Ltd | Real estate | 2021 |
| Jones Family Investments Group Limited | Financial services | 2022 |
| Jones Hedley Limited | Professional & scientific | 2018 |
| Jones Mart Limited | Wholesale & retail | 2025 |
| Jones the Dance CYF | Arts & recreation | 2015 |
| Jones the Foam Limited | Extraterritorial | 2018 |
| Jones Ward Estates Ltd | Real estate | 2025 |
| Jones Williams (Melin Corrwg) Limited | Construction | 2019 |
| Jones, Giles & Clay Limited | Professional & scientific | 2015 |
| Jones-Hughes Built Ltd | Construction | 2017 |
| Jonesco Limited | Hospitality | 2013 |
| Jonesdevelopments Limited | Construction | 2024 |
| Jonicee Co., Ltd | Extraterritorial | 2021 |
| Jonjonjon Ltd | Wholesale & retail | 2024 |
| Jonyte & Co Ltd | Construction | 2018 |
| Joodana Limited | Other services | 2025 |
| Joogee Pharma Ltd | Wholesale & retail | 2016 |
| Joon Dance | Arts & recreation | 2012 |
| Joostis Ltd | Wholesale & retail | 2020 |
| Jopa Consulting Limited | Information & communication | 1999 |
| Jor's Limited | Hospitality | 2017 |
| Jorade International Ltd | Wholesale & retail | 2016 |
| Jordan Home Developments Limited | Construction | 2011 |
| Jordan Homer Limited | Financial services | 2024 |
| Jordan Vehicles Ltd | Wholesale & retail | 2018 |
| Jorellix Ltd | Education | 2025 |
| Jorlon Ltd | Education | 2025 |
| Joro Group Ltd | Information & communication | 2025 |
| Jorob Consulting Limited | Administrative & support | 2019 |
| Jorvantis Ltd | Education | 2025 |