| Joe.T Health Limited | Health & social care | 2020 |
| JOGS96 UK Ltd | Other services | 2024 |
| John Burn & Company (Birmingham) Limited | Manufacturing | 1918 |
| John C Ltd | Transport & logistics | 2019 |
| John Carr Engineering Services Limited | Professional & scientific | 2017 |
| John Caswell Limited | Agriculture & fishing | 1980 |
| John Francise Limited | Information & communication | 2012 |
| John Louth Ltd | Professional & scientific | 2019 |
| John Mathieson Consulting Ltd | Professional & scientific | 2013 |
| John Toomer and Sons,Limited | Wholesale & retail | 1900 |
| Johnkez Ventures Limited | Information & communication | 2019 |
| Johnny Courier Ltd | Transport & logistics | 2019 |
| Johnson & Daltrey Ltd | Other services | 2012 |
| Johnson Capital Group Ltd | Financial services | 2026 |
| Johnson Gardening Services Ltd | Administrative & support | 2016 |
| Johnson Lawn Care Ltd | Administrative & support | 2023 |
| Johntrans Ltd | Transport & logistics | 2016 |
| Johny MM Ltd | Wholesale & retail | 2020 |
| Joint Forum Limited | Public administration | 2006 |
| Joint Operations (Spine) Ltd | Administrative & support | 2017 |
| Joint Operations (UK) LLP | | 2014 |
| Joint Operations Ltd | Professional & scientific | 2019 |
| Joisem Ltd | Public administration | 2020 |
| Jojo International UK Ltd | Administrative & support | 2022 |
| Jolanta Ltd | Health & social care | 2022 |
| Jolex Entertainment Ltd | Hospitality | 2025 |
| Jolivo Ltd | Health & social care | 2022 |
| Jollof & Beyond Limited | Hospitality | 2025 |
| Jollof Enterprise Ltd | Real estate | 2020 |
| Jolo Consulting Limited | Information & communication | 2013 |
| Jomados Consulting Limited | Professional & scientific | 2012 |
| JON Coogan Ltd | Arts & recreation | 2024 |
| Jonathan & Co PD Services Ltd | Construction | 2022 |
| Jonathan Goodfield Limited | Construction | 2015 |
| Jones & Co Estate Ltd | Real estate | 2020 |
| Jones Associate Ltd | Professional & scientific | 2021 |
| Jones Getaways Limited | Real estate | 2023 |
| Jones Wood Flooring Ltd | Construction | 2021 |
| Jongowe Ltd | Professional & scientific | 2023 |
| Jonkins Ltd | Professional & scientific | 2015 |
| Jopizale Limited | Information & communication | 2011 |
| Jordan Cobb Property Ltd | Real estate | 2025 |
| Jort Transport Limited | Transport & logistics | 2025 |
| Joseph Dark Marine Services Ltd | Administrative & support | 2014 |
| Joseph Enterprises Limited | Agriculture & fishing | 2008 |
| Josh Pratchett Limited | Arts & recreation | 2018 |
| Joshua Care Ltd | Health & social care | 2019 |
| Joshua Goldsworthy Hair Services Ltd | Other services | 2018 |
| Joshua P C Wiley Ltd | Financial services | 2026 |
| Jossen Ltd | Transport & logistics | 2022 |
| Jotox Ltd | Manufacturing | 2011 |
| Joule Consulting Limited | Professional & scientific | 2006 |
| JOV Systems Ltd | Information & communication | 2026 |
| Jovianne Ltd | Wholesale & retail | 2019 |
| Joykon Ltd | Wholesale & retail | 2023 |
| JP & JJ Construction Ltd | Construction | 2025 |
| JP Performing Arts Studios Limited | Arts & recreation | 2025 |
| Jpa&D Ltd | Transport & logistics | 2017 |
| JPK Construction Limited | Construction | 2006 |
| JPL Building Services Ltd | Construction | 2021 |
| JPR Legal Services Ltd | Professional & scientific | 2024 |
| JPS Testing Limited | Information & communication | 2007 |
| JR Cleaning & Maintenance Services Ltd | Administrative & support | 2020 |
| JR Heat Ltd | Construction | 2023 |
| JR Maintenance Limited | Construction | 2011 |
| JR Real Estate Investment Ltd | Real estate | 2026 |
| JRB Property Maintenance Ltd | Construction | 2014 |
| JRS Crop Protection Consultancy Ltd | Professional & scientific | 2020 |
| Jrsc- Courier Ltd | Transport & logistics | 2026 |
| JRT Logistics Ltd | Transport & logistics | 2023 |
| JRY Accountancy Ltd | Professional & scientific | 2025 |
| JS Hot Food Limited | Hospitality | 2025 |
| JSB Clear Consultancy Ltd | Professional & scientific | 2022 |
| JSD Tech Systems Ltd | Information & communication | 2026 |
| JSE Groundworks Limited | Construction | 2010 |
| JSK Heating Services Ltd | Construction | 2019 |
| JSM Recycling Ltd | Water & waste | 2020 |
| JST Business Consultants Ltd | Professional & scientific | 2021 |
| JSY Partnership LLP | | 2014 |
| JT 20 Ltd | Administrative & support | 2020 |
| JT Composites Ltd | Manufacturing | 2024 |
| JTC Capital Limited | Professional & scientific | 2011 |
| Jtd&Family Ltd | Other services | 2025 |
| Jtdt Management Services Ltd | Professional & scientific | 2017 |
| Jtembo Ltd | Administrative & support | 2026 |
| JTS Auto (Cheney Manor) Ltd | Wholesale & retail | 2024 |
| JTS Auto Swindon Limited | Wholesale & retail | 2024 |
| JTS Convenience Ltd | Wholesale & retail | 2025 |
| Jubail Park Developments Ltd | Real estate | 2007 |
| Jubilee Campus Living LLP | | 2026 |
| Juicy Designs Creative Limited | Professional & scientific | 2011 |
| Jujhar Transport Limited | Transport & logistics | 2017 |
| Julians Opportunities Ltd | Wholesale & retail | 2018 |
| Julie Benjamin HR Limited | Professional & scientific | 2023 |
| Julies Haven Ltd | Hospitality | 2024 |
| Julius Developments Limited | Real estate | 2021 |
| Jummiecosmetics Ltd | Wholesale & retail | 2025 |
| JUN Ltd | Information & communication | 2005 |
| Juniper Chautari Limited | Real estate | 2020 |
| Juniper Court (Newbury) Limited | Real estate | 2018 |