| Jklj Limited | Professional & scientific | 2018 |
| JKM Commerce Ltd | Wholesale & retail | 2026 |
| JL & Associates Limited | Administrative & support | 2006 |
| JL (MK) Properties Ltd | Real estate | 2023 |
| JL Freight Services Limited | Transport & logistics | 2016 |
| JL Global MAN & Van Services Milton Keynes Ltd | Transport & logistics | 2025 |
| JLF Moving Solutions Ltd. | Transport & logistics | 2011 |
| JLR80 Ltd | Wholesale & retail | 2026 |
| JLS Associates Limited | Education | 1999 |
| JLS Consult Limited | Professional & scientific | 2016 |
| JLS Electrician Ltd | Manufacturing | 2019 |
| JM Muya Healthcare Ltd | Health & social care | 2015 |
| JM Property (Souldrop) Limited | Real estate | 2020 |
| JM Renovations Services Ltd | Construction | 2025 |
| JM Spano Consultancy Ltd | Professional & scientific | 2018 |
| JMB Projects Limited | Professional & scientific | 2012 |
| JMC (MK) Limited | Professional & scientific | 2015 |
| JMC Analytics Ltd | Professional & scientific | 2025 |
| JMC Decorating Ltd | Construction | 2022 |
| JMC Homes Ltd | Real estate | 2018 |
| JMD Tech Limited | Information & communication | 2019 |
| JMD Visa and Air-Ticket Services Limited | Administrative & support | 2018 |
| Jmdomaingue Limited | Professional & scientific | 2019 |
| JME IT Transformation Consulting Limited | Information & communication | 2015 |
| Jmmkvr Limited | Information & communication | 2018 |
| JMN Business Solutions Limited | Wholesale & retail | 2009 |
| JMP Infotech Limited | Information & communication | 2017 |
| Jmqs Housing Ltd | Real estate | 2013 |
| JMS Ceilings Ltd | Construction | 2019 |
| JMS Data Solutions Limited | Construction | 2019 |
| JMS Films & Media Technologies Ltd | Information & communication | 2022 |
| JMS Infotech Limited | Information & communication | 2017 |
| JMS One Ltd | Information & communication | 2024 |
| Jnbk Ltd | Real estate | 2023 |
| JNJ Property Limited | Real estate | 2022 |
| JNK Sales & Services Limited | Real estate | 2025 |
| JNP Developments & Investments Ltd | Construction | 2012 |
| Jnrs Holdings Limited | Administrative & support | 2002 |
| Jnrs. Amusement Rides Limited | Arts & recreation | 2002 |
| JNY One Limited | Hospitality | 2026 |
| JO Maash Healthcare Limited | Health & social care | 2014 |
| Jo&Jo Ltd | Transport & logistics | 2014 |
| Jo&L Service Ltd | Construction | 2024 |
| Jo's Hope Ltd | Other services | 2017 |
| Joan Estates Ltd | Real estate | 2024 |
| Joan Technologies Ltd | Information & communication | 2024 |
| Joanne Bird Ltd | Administrative & support | 2025 |
| JOB Placement House Ltd | Administrative & support | 2024 |
| JOB Rocket Limited | Information & communication | 2018 |
| Jobec Golf Limited | Professional & scientific | 2014 |
| Jobic Ltd | Wholesale & retail | 2019 |
| Jobs Connect Recruitment Ltd | Other services | 2023 |
| Jobsz Done Ltd | Hospitality | 2014 |
| Jocan Build Ltd | Professional & scientific | 2023 |
| JOE & Frank Properties Limited | Real estate | 2018 |
| JOE Potter Consulting Limited | Information & communication | 2018 |
| Joenabel Ltd | Health & social care | 2020 |
| Joey's Gardens Ltd | Wholesale & retail | 2025 |
| Jofelz Distribution Ltd | Wholesale & retail | 2026 |
| Jogaya Transport Ltd | Transport & logistics | 2026 |
| Jogi Solutions Limited | Administrative & support | 2024 |
| Johav Care Support Healthcare Limited | Health & social care | 2020 |
| Johav Housing C.I.C. | Health & social care | 2024 |
| John Backhouse Associates Limited | Administrative & support | 2000 |
| John BE Tech Ltd. | Information & communication | 2015 |
| John Cawley Developments Limited | Real estate | 1936 |
| John D Scotcher Ltd | Information & communication | 2006 |
| John Dron Limited | Wholesale & retail | 1939 |
| John E Stubbs Consulting UK Limited | Professional & scientific | 2013 |
| John Fernandez Catering Ltd | Hospitality | 2012 |
| John Garage UK Ltd | Wholesale & retail | 2025 |
| John Jones Ltd | Extraterritorial | 2026 |
| John Morris Plant Hire Limited | Construction | 2024 |
| John Osbourne Contracting Limited | Construction | 2016 |
| John Peace Paintings Limited | Other services | 2020 |
| John Sibley Ltd | Education | 2016 |
| John Terroni Photography Limited | Professional & scientific | 2013 |
| John the Mechanic Ltd | Wholesale & retail | 2020 |
| John Unwin (Electrical Contractors) Limited | Construction | 1967 |
| John Whittle Robinson Limited | Professional & scientific | 2012 |
| John Woods Holdings Limited | Financial services | 2018 |
| Johndevelops Ltd | Information & communication | 2017 |
| Johnflo Ltd | Health & social care | 2020 |
| Johnnytrims Ltd | Other services | 2025 |
| Johnson & Cooper Properties Ltd | Real estate | 2022 |
| Johnson Business Consulting Limited | Administrative & support | 2012 |
| Johnson Law Associates Ltd | Information & communication | 2019 |
| Johnson Tiling Limited | Construction | 2025 |
| Johnson's Driving Academy Ltd | Education | 2014 |
| Johnson's Professional Services Agency Limited | Administrative & support | 2021 |
| Johnston Fine Arts Limited | Wholesale & retail | 2013 |
| Joinery by Oakvale Limited | Construction | 2011 |
| Joint Futures Limited | Health & social care | 2006 |
| Joint Retail Logistics Limited | Professional & scientific | 1984 |
| Joint Solutions MK Limited | Health & social care | 2010 |
| Jokelab Limited | Hospitality | 2024 |
| Joker.Com Limited | Information & communication | 2009 |
| Jokhaali Ltd | Administrative & support | 2018 |
| Jolex Cars Ltd | Wholesale & retail | 2023 |
| Jolly Monkey Productions Limited | Information & communication | 2018 |