| Julian Flynn Ortho Ltd | Health & social care | 2010 |
| Julian Margaret Limited | Administrative & support | 2025 |
| Julie & Niamh Limited | Wholesale & retail | 2010 |
| Julun Limited | Real estate | 2024 |
| Jumelles Properties Limited | Real estate | 2021 |
| Jumiere Limited | Professional & scientific | 2023 |
| Jumpo Cleaning Services(London) Ltd | Administrative & support | 2024 |
| Junction Property 2 Limited | Real estate | 2022 |
| Junction Property Limited | Real estate | 2018 |
| June Cadogan Creative Ltd | Arts & recreation | 2008 |
| June Consulting Services Ltd | Information & communication | 2025 |
| June London Limited | Manufacturing | 2008 |
| June Property Solutions Limited | Real estate | 2023 |
| Juniper Court (Hounslow) RTM Company Limited | Households | 2025 |
| Junk Freddy Ltd | Water & waste | 2023 |
| Jupilike Limited | Wholesale & retail | 2016 |
| Jupiter Asset Ltd | Professional & scientific | 2023 |
| Jupiter Group London Ltd | Transport & logistics | 2021 |
| Jupiter Orbit Ltd | Information & communication | 2010 |
| Just Airports Limited | Other services | 2002 |
| Just Airports.Com Limited | Other services | 2002 |
| Just Amendments Ltd | Manufacturing | 2025 |
| Just Easy Bathing Ltd | Construction | 2019 |
| Just Films Ltd | Information & communication | 2021 |
| Just Flights and Parcels Ltd | Administrative & support | 2022 |
| Just Food Shipping Company Limited | Wholesale & retail | 2019 |
| Just in Time Maintenance Ltd | Construction | 2025 |
| Just India Limited | Hospitality | 2014 |
| Just JED Limited | Professional & scientific | 2020 |
| Just Jobs Recruiters Ltd | Administrative & support | 2023 |
| Just Jooste Ltd | Professional & scientific | 2016 |
| Just Looking Press Ltd | Information & communication | 2023 |
| Just Right Accountancy Limited | Professional & scientific | 2016 |
| Just the Car Ltd | Wholesale & retail | 2009 |
| Just There Ltd | Information & communication | 2024 |
| Just US People Ltd | Administrative & support | 2024 |
| Justballoons Limited | Wholesale & retail | 2018 |
| Justbuy 9 Ltd | Real estate | 2023 |
| Justdene Limited | Professional & scientific | 1982 |
| Juste Macarons Plus Limited | Hospitality | 2022 |
| Justneat Services Ltd | Wholesale & retail | 2023 |
| Justri Limited | Professional & scientific | 2011 |
| Juve Construction Limited | Construction | 2025 |
| Juvee Ltd | Real estate | 2016 |
| Juventus Corporation (UK) Limited | Real estate | 2015 |
| JV Electric Ltd | Construction | 2022 |
| JV Property Group Limited | Real estate | 2021 |
| JVE Retail Ltd | Wholesale & retail | 2023 |
| JVK Hallsell Limited | Manufacturing | 2025 |
| JVP Property Trading Limited | Real estate | 2017 |
| JVP Ventures Ltd | Wholesale & retail | 2025 |
| JVR Associates Ltd | Professional & scientific | 2023 |
| JW Longevity Limited | Construction | 2024 |
| JW Protection Ltd | Administrative & support | 2023 |
| JW Stag Ltd | Professional & scientific | 2025 |
| JW Surgical Limited | Health & social care | 2019 |
| JW Waste Management Limited | Water & waste | 2016 |
| Jwala TEJ Pratap Singh Cricket Academy UK Ltd | Arts & recreation | 2025 |
| JWJ Entertainment Ltd | Arts & recreation | 2022 |
| JXK Limited | Other services | 2013 |
| Jyant Solutions Limited | Information & communication | 2013 |
| Jycly Limited | Arts & recreation | 2024 |
| JYL Properties Limited | Real estate | 2025 |
| JYM Consultancy Limited | Professional & scientific | 2019 |
| Jyoti Holdings Ltd | Real estate | 2017 |
| Jyotsna Electrical Limited | Wholesale & retail | 2003 |
| Jyvi Consultant Ltd. | Financial services | 2014 |
| Jywal London Ltd | Wholesale & retail | 2017 |
| J’Adore Cakes Ltd | Wholesale & retail | 2021 |
| K & a Patel Ltd | Wholesale & retail | 2022 |
| K & D Assets LLP | | 2021 |
| K & D Distribution Ltd | Real estate | 2012 |
| K & H Enterprises Limited | Real estate | 2015 |
| K & H Trading Ltd | Professional & scientific | 2025 |
| K & K Global Ventures Ltd | Wholesale & retail | 2025 |
| K & K Stores Limited | Wholesale & retail | 2005 |
| K & N P Ltd | Wholesale & retail | 2025 |
| K & S Engineering and Scientific Limited | Professional & scientific | 1994 |
| K & S Professional Resources Limited | Professional & scientific | 2017 |
| K a Impex Ltd | Wholesale & retail | 2021 |
| K a Plumbing & Heating Limited | Construction | 2017 |
| K Art Investments Limited | Real estate | 2024 |
| K Chawda Investments Limited | Real estate | 2024 |
| K Create Art Ltd | Information & communication | 2021 |
| K Engineering Ltd | Construction | 2023 |
| K H Patel Limited | Wholesale & retail | 2025 |
| K J D Builders Limited | Construction | 2005 |
| K J Divine Care Ltd | Health & social care | 2018 |
| K Korner Ltd | Hospitality | 2026 |
| K KUK Limited | Professional & scientific | 2016 |
| K M Health Limited | Health & social care | 2012 |
| K Medica Limited | Health & social care | 2019 |
| K N G IT Solutions Limited | Information & communication | 2018 |
| K P 28 Food & Drinks Ltd | Hospitality | 2025 |
| K R Residentials Ltd | Real estate | 2015 |
| K S Cars & Couriers Ltd | Administrative & support | 2011 |
| K S P Property Limited | Real estate | 2020 |
| K SAM & Co Limited | Professional & scientific | 2011 |
| K Star Property Solutions Ltd | Construction | 2016 |
| K T M Europe Limited | Wholesale & retail | 2007 |