| Jeffery Weeks Consulting Limited | Professional & scientific | 2007 |
| Jeffreyai Ltd | Information & communication | 2023 |
| Jega 2 Limited | Professional & scientific | 2023 |
| Jelley Farming Ltd | Agriculture & fishing | 2014 |
| Jelly (Holdings) Limited | Financial services | 2014 |
| Jelly Communications Limited | Information & communication | 2005 |
| Jemini Scientific Limited | Professional & scientific | 2008 |
| Jeni Tennison Consulting Ltd | Information & communication | 2021 |
| Jenkspay Limited | Professional & scientific | 2026 |
| Jennaconsulting Limited | Administrative & support | 2025 |
| Jennings Surfacing Limited | Construction | 1999 |
| Jennison Tandy Limited | Administrative & support | 2020 |
| Jeppesen Heaton,Limited | Transport & logistics | 1947 |
| Jeremy Davidson Limited | Real estate | 2024 |
| Jeremy Taylor Architecture Ltd | Professional & scientific | 2019 |
| Jers Retail Ltd | Wholesale & retail | 2025 |
| Jessamy Property Limited | Real estate | 2021 |
| Jesse Williams Limited | Construction | 2020 |
| Jessica Rose Aesthetics & Cosmetic Clinic Ltd | Other services | 2023 |
| Jessica Rose Aesthetics Ltd | Other services | 2021 |
| Jesters Party Shop Limited | Wholesale & retail | 2006 |
| Jett Enterprises Ltd | Information & communication | 2015 |
| Jeydi Property Services Limited | Real estate | 2025 |
| JF Heating Ltd | Construction | 2021 |
| JFJ Homes Limited | Real estate | 2023 |
| JFL Electrical Services Ltd | Construction | 2007 |
| Jgls Property Limited | Real estate | 2007 |
| JGS Fabrications Limited | Construction | 2020 |
| JH Carpentry & Joinery Limited | Manufacturing | 2021 |
| JH Pro Plastering Limited | Construction | 2015 |
| Jigzag Limited | Administrative & support | 2018 |
| Jill Streater Music Limited | Information & communication | 2012 |
| JIM Boyle Racing Limited | Administrative & support | 2017 |
| JIM Building Services Ltd | Construction | 2021 |
| JIN Line Ltd | Health & social care | 2025 |
| JIO Enterprises Ltd | Wholesale & retail | 2024 |
| JJ Construct Ltd | Construction | 2022 |
| JJ Metals & Alloys Limited | Wholesale & retail | 2023 |
| JJ Morgan Property Limited | Real estate | 2025 |
| JJ Trotter Ltd | Information & communication | 2019 |
| JJCR1 Ltd | Professional & scientific | 2024 |
| JJS Plastering Contractors (Surrey) Limited | Administrative & support | 2017 |
| Jjst Ltd | Information & communication | 2021 |
| JJW1 Ltd | Real estate | 2020 |
| JK (UK) OHC Limited | Administrative & support | 2020 |
| JK Property Consultancy Limited | Real estate | 2024 |
| JL Lopes Ltd | Hospitality | 2017 |
| JLA Distribution Ltd | Wholesale & retail | 2023 |
| JLM Ventures Limited | Real estate | 2022 |
| JM Environmental Ltd | Administrative & support | 2013 |
| Jmen Consulting Limited | Professional & scientific | 2017 |
| Jmorrisonfitness Ltd | Health & social care | 2024 |
| JNA Developments (London) Limited | Construction | 2011 |
| JNH Corporation Ltd | Wholesale & retail | 2019 |
| JO Harcourt Productions Limited | Information & communication | 2012 |
| JO Love Intuitive Design Limited | Professional & scientific | 2024 |
| Joanna Beauty Limited | Other services | 2015 |
| Joanna Lott Coaching Ltd | Professional & scientific | 2023 |
| Jodhani Enterprise Ltd | Wholesale & retail | 2024 |
| Jogs Athletics Limited | Arts & recreation | 2013 |
| John Carter Flowers (London) Limited | Wholesale & retail | 2025 |
| John Conroy Limited | Administrative & support | 1949 |
| John Cornell Builders Limited | Construction | 1978 |
| John L Cars (Mitcham) Limited | | 1984 |
| John Lovell(Merchandisers)Limited | Real estate | 1948 |
| John Lukey & Sons Limited | Other services | 1900 |
| John M Southern Solutions Limited | Professional & scientific | 2020 |
| John Massey Consulting Ltd | Financial services | 2009 |
| John Miles Agents Limited | Real estate | 2017 |
| John Perkins Projects Ltd | Construction | 2002 |
| John Street & Company(Surrey)Limited | Real estate | 1949 |
| Johnson Associates (UK) Ltd | Professional & scientific | 2011 |
| Johnson Associates Group Limited | Professional & scientific | 2021 |
| Johnson Developments (South East) Limited | Construction | 2015 |
| Johnson's Property & Mortgage Services Limited | Financial services | 2018 |
| Johnston Solutions Limited | Information & communication | 2017 |
| Joint Potential Ltd | Professional & scientific | 2019 |
| Jolly Jumpers Limited | Education | 2009 |
| JON Wilkins Ltd | Real estate | 2025 |
| Jonas Partners Limited | Real estate | 2013 |
| Jonathan George Consultancy Ltd | Professional & scientific | 2021 |
| Jonathan Timpson (JT) Photography Ltd | Hospitality | 2012 |
| Jonathan Timpson Consulting Services Ltd | Other services | 2022 |
| Jonathan Webb Limited | Health & social care | 2002 |
| Jones Davies Ltd | Real estate | 2018 |
| Jones Lang Lasalle Americas, Inc Ltd | Real estate | 2025 |
| Jordan Kelsey Ltd | Professional & scientific | 2022 |
| Jordans Properties Ltd | Real estate | 2022 |
| Josef Seibel UK Limited | Wholesale & retail | 2004 |
| Josh Gluckstein Artist Ltd | Arts & recreation | 2023 |
| Joyede Limited | Other services | 2011 |
| JP Living Construction Limited | Construction | 2023 |
| JP Living Holdings Ltd | Real estate | 2025 |
| JP Living Limited | Real estate | 2022 |
| JP Moran Media Limited | Administrative & support | 2016 |
| JP People & Business Solutions Ltd | Professional & scientific | 2021 |
| JPG Media Ltd | Information & communication | 2017 |
| JPJ Wellbeing Ltd | Other services | 2021 |
| JR Holdco Limited | Financial services | 2026 |
| JR Russell Limited | Professional & scientific | 2024 |