| Jaxons & Co Holdings Limited | Administrative & support | 2025 |
| Jaxons Contracts Limited | Administrative & support | 2024 |
| Jaxons Warehouse Ltd | Wholesale & retail | 2023 |
| JAY MAC Plumbing & Heating Limited | Construction | 2016 |
| JAY MAC Properties Limited | Real estate | 2021 |
| JAY Resources Limited | Administrative & support | 2004 |
| JBC Building Services Limited | Construction | 2018 |
| Jbhe Consultancy Ltd | Information & communication | 2025 |
| JC Climate Control Ltd | Construction | 2025 |
| JC Hospitality Services Ltd | Hospitality | 2026 |
| JC Projects & Consulting Services Limited | Professional & scientific | 2024 |
| JC Strategy Consulting Ltd | Information & communication | 2024 |
| Jc-Df Properties Ltd | Real estate | 2022 |
| JCP Electrical Limited | Construction | 2026 |
| Jcsc Limited | Financial services | 2026 |
| JD Insignia Limited | Construction | 2010 |
| JDC Lettings Ltd | Real estate | 2021 |
| Jdmarie Limited | Construction | 2025 |
| JDT Comms Ltd | Construction | 2023 |
| Jeakins Bros. Commercials Limited | Wholesale & retail | 1988 |
| JEM Studios Limited | Other services | 2024 |
| Jemi Studios Ltd | Information & communication | 2026 |
| Jenbar Limited | Professional & scientific | 2004 |
| Jennifer Stock Limited | Professional & scientific | 2013 |
| Jenny's Properties Ltd | Real estate | 2020 |
| JET & Drain Ltd | Construction | 2008 |
| JET Stream Cleaning Ltd | Administrative & support | 2019 |
| JGR Development Ltd | Professional & scientific | 2016 |
| JH Property Maintenance Limited | Construction | 2013 |
| JHJ Interiors Ltd | Construction | 2020 |
| Jino's Desserts Limited | Hospitality | 2024 |
| JJ Holdings (London) Limited | Financial services | 2024 |
| JJB Automotive Ltd | Professional & scientific | 2025 |
| JJK Software Ltd | Information & communication | 2025 |
| Jjok Limited | Hospitality | 2025 |
| Jjvf Group Ltd | Professional & scientific | 2019 |
| JK Coach Ltd | Professional & scientific | 2019 |
| JK Traditional Barbers Ltd | Other services | 2019 |
| JKL Print Limited | Manufacturing | 2010 |
| JKS Boxing Limited | Arts & recreation | 2024 |
| JL Reddey Properties Limited | Real estate | 2022 |
| JLC Solutions Limited | Professional & scientific | 2019 |
| JLR Engine Specialists Ltd | Wholesale & retail | 2025 |
| JLS Holdings Limited | Information & communication | 2012 |
| JM Thermo Flow Ltd | Construction | 2025 |
| JME Builds Ltd | Construction | 2017 |
| JND Cardiology Ltd | Health & social care | 2017 |
| Jnic Transport Limited | Transport & logistics | 2009 |
| JNL Homes Limited | Real estate | 2022 |
| JO Read Limited | Professional & scientific | 2014 |
| Joaden Ventures UK Ltd | Other services | 2014 |
| Joalten Investments Limited | Real estate | 1973 |
| Jodami Limited | Professional & scientific | 2011 |
| JOE Tilley Roofing Limited | Construction | 2017 |
| Joff LEE Studio Limited | Professional & scientific | 2020 |
| John Dutfield LLP | | 2010 |
| John Ritchie Analysis Limited | Information & communication | 2018 |
| Johnson Construction Consultants Ltd | Professional & scientific | 2025 |
| Johnson Interiors Solutions Limited | Construction | 2019 |
| Johnson Stevens International Forwarding Limited | Other services | 1978 |
| Johnsonco Limited | Construction | 2007 |
| Jonathan Ashe Architects Limited | Professional & scientific | 2011 |
| Jonny Watson Consulting Limited | Professional & scientific | 2018 |
| JOR Electrical Ltd | Construction | 2020 |
| Jordan Marsh & Consulting Ltd | Professional & scientific | 2023 |
| Joseph Lionel Property Ltd | Real estate | 2026 |
| Josh Mccain Ltd | Construction | 2025 |
| Joshon Solutions Ltd | Professional & scientific | 2020 |
| JP Creative Group Limited | Professional & scientific | 2024 |
| JP Creative Holdings Limited | Professional & scientific | 2022 |
| JP Creative Limited | Professional & scientific | 2002 |
| JP Digital Drafting Limited | Professional & scientific | 2021 |
| JP Signalling Ltd | Construction | 2021 |
| JPS Building and Construction Ltd | Construction | 2025 |
| Jpst Management Limited | Real estate | 2025 |
| JRL Productions Limited | Information & communication | 2013 |
| Jrmj Holdings Ltd | Real estate | 2021 |
| JS ASH Ltd | Information & communication | 2017 |
| JS ASH Property Limited | Real estate | 2022 |
| JS ASH Propertymanagement Ltd | Real estate | 2022 |
| JS Startup Consulting Ltd | Professional & scientific | 2024 |
| JSB Heating Limited | Construction | 2014 |
| JSB Retail Services Ltd | Manufacturing | 2012 |
| JSC Heating & A/C Ltd | Construction | 2024 |
| JSC UK Holdings Limited | Information & communication | 2025 |
| JSO Isolations Limited | Construction | 2018 |
| JT Risk & Finance Consulting Ltd | Professional & scientific | 2025 |
| JTD Accounts Ltd | Administrative & support | 2016 |
| Jude Livestock Ltd | Agriculture & fishing | 2023 |
| Junior Jurassic's Ltd | Arts & recreation | 2023 |
| Just a Mortgage Limited | Financial services | 2018 |
| Just for Lunch and Dinner Limited | Health & social care | 2026 |
| Just Layed Flooring Limited | Construction | 2013 |
| Just Lunch OR Dinner Limited | Health & social care | 2026 |
| Just Mijas Limited | Administrative & support | 2008 |
| Just Most Ltd | Hospitality | 2018 |
| Just Run OUT Office Supplies Ltd | Administrative & support | 2011 |
| JW Group Holdings Ltd | Financial services | 2023 |
| JW Network Solutions Ltd | Other services | 2017 |
| JW Utilities and Infrastructure Ltd | Construction | 2023 |