| JK Parata Developments Limited | Construction | 2023 |
| JK Rockshire Ltd | Real estate | 2022 |
| JKS Transport Ltd | Transport & logistics | 2018 |
| Jksc Services Ltd | Health & social care | 2014 |
| JL & JS Blessed Housing Empire Ltd | Real estate | 2026 |
| JL Advisors Limited | Professional & scientific | 2010 |
| JL Living Quarters Limited | Real estate | 2018 |
| JM Security Solution Limited | Administrative & support | 2025 |
| JMB PAY Limited | Administrative & support | 2019 |
| Jmbp Design & Training Limited | Information & communication | 2011 |
| JMC Leisure Limited | Other services | 2008 |
| JMH1 Ltd | Transport & logistics | 2024 |
| Jmka Education Ltd | Education | 2020 |
| Jobs on TAP | Administrative & support | 2019 |
| JOE Roberson Fitness Ltd | Arts & recreation | 2024 |
| Joe's Restaurants Limited | Hospitality | 2005 |
| Johana Willa Limited | Wholesale & retail | 2021 |
| John Ball Limited | Professional & scientific | 2018 |
| John Burder Construction Limited | Construction | 2011 |
| John Harwood Limited | Construction | 2019 |
| John Haynes Limited | Construction | 2011 |
| John Lord Ltd. | Professional & scientific | 2008 |
| John Luscombe & Co. Limited | Mining & quarrying | 2018 |
| John Moore Heritage Services Ltd | Professional & scientific | 2016 |
| John Newbigin Limited | Professional & scientific | 2012 |
| John P.Gee & Sons Limited | Agriculture & fishing | 1957 |
| John Parry Estates Limited | Real estate | 1949 |
| John Parry Holdings Limited | Real estate | 2017 |
| John Werrell & SON Limited | Transport & logistics | 1956 |
| John, George Pimm & Sons (Eynsham) Limited | Construction | 2023 |
| John, George Pimm & Sons Holdings Limited | Construction | 2023 |
| John,George Pimm & Sons Limited | Construction | 1961 |
| Johnston Cave Associates Ltd | Professional & scientific | 1986 |
| Jojo's Cafe Bar Ltd | Hospitality | 2020 |
| Jolly Face Ltd | Information & communication | 2018 |
| Joly Sky Ltd | Professional & scientific | 2025 |
| JON Hartley & Associates Limited | Professional & scientific | 2009 |
| JON Holmans Fitness Limited | Other services | 2013 |
| JON Rees Associates Ltd | Professional & scientific | 2015 |
| Joscat Ltd | Health & social care | 2019 |
| Joshua Dubin Ltd | Professional & scientific | 2015 |
| Josias Vending Ltd | Wholesale & retail | 2024 |
| Jostaninterbiz UK Ltd | Wholesale & retail | 2013 |
| Joucques Editions Ltd | Information & communication | 2019 |
| Journal of Chinese Economic and Business Studies Limited | Information & communication | 2007 |
| Joy Plus Care Ltd | Administrative & support | 2023 |
| Joy Plus Store Ltd | Wholesale & retail | 2025 |
| Joy's Afro Caribbean &Beauty Ltd | Other services | 2020 |
| Joysweet Ltd | Administrative & support | 2025 |
| JP Buckley Aerodynamics Limited | Professional & scientific | 2013 |
| JP Polishing Limited | Other services | 2019 |
| JP XP Ltd | Construction | 2025 |
| JPH (Management) Ltd | Professional & scientific | 2019 |
| JPH Group Ltd | Professional & scientific | 2016 |
| JPR Wine Consultancy Limited | Professional & scientific | 2012 |
| Jprb Limited | Professional & scientific | 2009 |
| Jr&S Building Management Ltd | Construction | 2025 |
| JRD Studios Ltd | Wholesale & retail | 2020 |
| Jread Advocacy, Consultancy & Admin Services Ltd | Information & communication | 2016 |
| JRG Logistics Ltd | Transport & logistics | 2024 |
| JRG2 Ltd | Wholesale & retail | 2026 |
| Jria Enterprises Ltd | Real estate | 2023 |
| JRS Smart Repairs Ltd | Wholesale & retail | 2015 |
| JS UK Corporation Ltd | Wholesale & retail | 2021 |
| JSK Building and Property Maintenance Ltd | Construction | 2017 |
| JSL Consultancy Ltd | Professional & scientific | 2015 |
| JSL Consulting Limited | Professional & scientific | 2000 |
| JSL5CONSTRUCTION Limited | Construction | 2023 |
| JSM Everyday Services Ltd | Health & social care | 2020 |
| JSW Property Limited | Real estate | 2013 |
| JSX Direct Ltd | Wholesale & retail | 2026 |
| JT Marine Ltd | Manufacturing | 2023 |
| JTB Taverns Limited | Hospitality | 2016 |
| JTU Property Maintenance & Development Ltd | Construction | 2026 |
| Jubilee House Advisors Ltd | Professional & scientific | 2020 |
| Jubilee Mews Residents' Management Company Limited | Households | 2025 |
| Judris Management Limited | Professional & scientific | 2009 |
| Jugglers ETC Limited | Arts & recreation | 2002 |
| Juhi's Restaurant Ltd | Hospitality | 2024 |
| Jules and Field Limited | Professional & scientific | 2018 |
| Julian Clark Limited | Professional & scientific | 2009 |
| Julian Wilcox Ltd. | Information & communication | 2011 |
| Juliet Biological Technologies Ltd | Information & communication | 2025 |
| Jump in Puddles Consultancy Ltd | Professional & scientific | 2020 |
| Jumuah Enterprises Ltd | Education | 2014 |
| Juncture Building Consultancy Limited | Professional & scientific | 2020 |
| Junior Touring Car Limited | Arts & recreation | 2021 |
| Juniper Interiors Ltd | Professional & scientific | 2026 |
| Junksy Ltd | Water & waste | 2023 |
| Juno Genetics Ltd | Health & social care | 2016 |
| Junoon Aurum Mehfil Ltd | Wholesale & retail | 2026 |
| Jupiter Activities Ltd | Wholesale & retail | 2019 |
| Juris Consultants Limited | Professional & scientific | 2007 |
| Just Emergency Ltd | Health & social care | 2013 |
| Just Purple Limited | Professional & scientific | 2003 |
| Justadvisorsbp Ltd | Professional & scientific | 2024 |
| Justcleaners Limited | Administrative & support | 2025 |
| Justice Enterprises (Global) Ltd | Wholesale & retail | 2025 |
| Justice for Frontline Staff Limited | Manufacturing | 2019 |
| Justin Barrett Property Maintenance Services Ltd | Extraterritorial | 2024 |