| JLA Holdings Limited | Financial services | 2023 |
| Jlaja Ltd | Real estate | 2018 |
| JLC Transport Limited | Transport & logistics | 2013 |
| Jllh Holdings Ltd | Financial services | 2024 |
| JLM Independent Wealth Management Ltd | Administrative & support | 2011 |
| JLM Master Brokers Hitchin Ltd | Financial services | 2018 |
| JLM Master Brokers Ltd | Financial services | 2023 |
| JLM Mortgage Brokers Ltd | Financial services | 2021 |
| JLM Mortgage Network Ltd | Financial services | 2003 |
| JLM Network Wealth Limited | Financial services | 2023 |
| JLM North London Limited | Financial services | 2025 |
| JLM Protection Limited | Financial services | 2021 |
| JLM Wills and Estate Planning Limited | Professional & scientific | 2025 |
| Jlmmn Holding Limited | Financial services | 2022 |
| JLR Autocare Ltd | Wholesale & retail | 2022 |
| JLR Events Ltd | Arts & recreation | 2025 |
| JLR Motorsport Ltd | Wholesale & retail | 2026 |
| JLR Property Investments Limited | Real estate | 2019 |
| JLS Group Ltd | Wholesale & retail | 2020 |
| JLS Scaffolding Services Limited | Construction | 2018 |
| JM Marylebone Limited | Real estate | 2018 |
| JM Marylebone Properties Ltd | Real estate | 2023 |
| JM Sparrows Electrical Ltd | Construction | 2023 |
| JMB Waste Solutions Ltd | Water & waste | 2025 |
| JMC Setton Limited | Information & communication | 2022 |
| JMF Electrical Contractors Limited | Construction | 2017 |
| JMG Grips Ltd | Information & communication | 2019 |
| Jmkterry Ltd | Real estate | 2022 |
| Jmtjat Holdings Ltd | Financial services | 2018 |
| Jnrs Workshop Ltd | Manufacturing | 2016 |
| JO Cleary Coaching and Leadership Development Limited | Professional & scientific | 2024 |
| JO Driver Ltd | Administrative & support | 2021 |
| JO Mylles Education Ltd | Education | 2025 |
| Joanne Chung Limited | Financial services | 2026 |
| Joel Cleaning Services Limited | Administrative & support | 2021 |
| Joes Vintage Limited | Wholesale & retail | 2023 |
| John Burgess & Co. Limited | Construction | 1948 |
| John COX Car & Commercials Limited | Wholesale & retail | 2009 |
| John RAY Limited | Construction | 1928 |
| John Rayner Farms Limited | Agriculture & fishing | 1978 |
| John Shilcock Limited | Construction | 1990 |
| Johnarc Ltd | Construction | 2014 |
| Johnsjobs Ltd | Water & waste | 2017 |
| Jojo Glow London Ltd | Other services | 2022 |
| Jomuco Property Ltd | Real estate | 2022 |
| JON Archer - Real Estate Broker UK Ltd | Real estate | 2020 |
| JON Hunt Associates Limited | Information & communication | 1998 |
| JON Kent Electrical Services Ltd | Construction | 2010 |
| Jones Hunt Limited | Professional & scientific | 2016 |
| Jonroo Buildings Ltd | Real estate | 2019 |
| Jopris Health Care Services Ltd | Health & social care | 2023 |
| Jordans Commercial Interiors Limited | Construction | 2011 |
| Joseph Luke Property Ltd | Real estate | 2016 |
| Josh Campbell Design Ltd | Professional & scientific | 2022 |
| Journeys Bound Ltd | Information & communication | 2010 |
| Jowett Design & Consulting Ltd | Professional & scientific | 2024 |
| Joy & Josh Properties Ltd | Real estate | 2025 |
| JPC Foods Ltd | Wholesale & retail | 2021 |
| Jplondonartadvisory Ltd | Wholesale & retail | 2025 |
| JPS Construction (Herts) Ltd | Construction | 2023 |
| JPS Surfacing Ltd | Construction | 2024 |
| JR Designed Limited | Professional & scientific | 2018 |
| JR Refrigeration Ltd | Administrative & support | 2015 |
| JRT Properties Limited | Real estate | 2020 |
| JS Hatch Limited | Real estate | 2026 |
| JSH Property Investments Limited | Real estate | 2014 |
| Jshells Ltd | Manufacturing | 2018 |
| JSO Carpentry & Joinery Limited | Professional & scientific | 2023 |
| JST Properties Limited | Real estate | 2001 |
| JTC28 Limited | Real estate | 2026 |
| Jude Brooks Limited | Professional & scientific | 2014 |
| Judge & Sons Building Services Ltd | Construction | 2024 |
| Judy Willits Consulting Limited | Professional & scientific | 2005 |
| Juliette Mcgill Limited | Arts & recreation | 2013 |
| Jumbler Limited | Professional & scientific | 2010 |
| Junglemajor Limited | Information & communication | 1994 |
| Just Face Painting Limited | Other services | 2022 |
| Just in Solutions Ltd | Professional & scientific | 2020 |
| Just Scaffolding Hertfordshire Limited | Construction | 2024 |
| Just Spray Ltd | Construction | 2018 |
| Justginger Limited | Construction | 2007 |
| Justin Colours Ltd | Construction | 2006 |
| Jvsp Properties Limited | Real estate | 2019 |
| JWL Enterprises (DUB) Limited | Construction | 2015 |
| JZ Investments Limited | Households | 2021 |
| J’S Sports Agent Consultancy Ltd | Arts & recreation | 2022 |
| K & M Engineering Limited | Manufacturing | 2011 |
| K a Hotels Ltd | Hospitality | 2018 |
| K Dhami Limited | Information & communication | 2023 |
| K G Croft General Building Contractors Ltd | Construction | 2005 |
| K Jones Butchers Limited | Wholesale & retail | 2012 |
| K K Care Services Ltd | Professional & scientific | 2020 |
| K L Giddings Holdings Limited | Financial services | 2017 |
| K.G.T.Investment Company Limited | Real estate | 1960 |
| K.L.F. Limited | Information & communication | 1994 |
| K4 Plus Systems Limited | Information & communication | 2000 |
| KAB HR Services Ltd | Administrative & support | 2024 |
| Kairon Trading UK Limited | Wholesale & retail | 2022 |
| Kalirai Investments Limited | Real estate | 2019 |
| Kalirai Capital Partners Limited | Financial services | 2018 |