| J&L 1 Limited | Transport & logistics | 2022 |
| J&P Travel Ltd | Transport & logistics | 2024 |
| J&Tconstruction Services Ltd | Construction | 2011 |
| J.R.E Management Consulting Ltd | Professional & scientific | 2024 |
| J40 Media Ltd | Information & communication | 2023 |
| JA Property Consultancy Ltd | Real estate | 1999 |
| Jabo Partners Ltd | Professional & scientific | 2019 |
| Jackdan Consultants Limited | Construction | 2018 |
| Jackson Young Limited | Administrative & support | 2009 |
| Jadoun Properties Ltd | Administrative & support | 2017 |
| Jagcorp Enterprises Ltd | Information & communication | 2018 |
| JAI10 Limited | Manufacturing | 2024 |
| Jain Homes Limited | Real estate | 2022 |
| JAJ Trading Ltd | Wholesale & retail | 2025 |
| James & Taylor Limited | Wholesale & retail | 1987 |
| James and Sarah King Limited | Professional & scientific | 2015 |
| James Andrew Smith Web Development Ltd | Information & communication | 2019 |
| James Dollah Ltd | Professional & scientific | 2026 |
| James Hannigan Music Limited | Information & communication | 2011 |
| Jamik Properties Limited | Real estate | 2020 |
| Jamix Limited | Information & communication | 2018 |
| Japanese Car Importers Ltd | Wholesale & retail | 2023 |
| JAR Properties (Surrey) Ltd | Real estate | 2022 |
| Jara Place Ltd | Health & social care | 2025 |
| Jasmine Academy Ltd | Education | 2019 |
| Jatkowska Ltd | Health & social care | 2021 |
| JAW Electrical 7 Ltd | Manufacturing | 2020 |
| JAY Cowie Photography Limited | Professional & scientific | 2012 |
| Jay-Mac Associates Ltd | Construction | 2025 |
| JCG Electical Ltd | Construction | 2026 |
| JCK Real Estate Ltd | Real estate | 2018 |
| JCR Homes Limited | Real estate | 2023 |
| Jcvnm Limited | Hospitality | 2020 |
| JD Books Ltd. | Professional & scientific | 2019 |
| JD Skills School Ltd | Arts & recreation | 2023 |
| Jdstudios UK Limited | Information & communication | 2011 |
| Jedi's Leisure Limited | Hospitality | 2016 |
| JEL International Limited | Information & communication | 2022 |
| JEM Smart Money Limited | Real estate | 2020 |
| Jenson Steed International Limited | Professional & scientific | 2024 |
| Jericho Estates Ltd | Construction | 2020 |
| Jericho Media (Comms) Ltd | Professional & scientific | 2023 |
| Jericho Trading UK Ltd | Real estate | 2021 |
| Jerug Limited | Professional & scientific | 2006 |
| Jewel Bespoke Build Ltd | Construction | 2021 |
| Jewel Dream Homes Ltd | Construction | 2022 |
| Jewel Enterprises Ltd | Professional & scientific | 2024 |
| Jewel Passive Fire Protection Ltd | Public administration | 2019 |
| JF Construction Services Limited | Construction | 2008 |
| Jhkl Ltd | Professional & scientific | 2023 |
| Jhls Studio Ltd | Professional & scientific | 2020 |
| Jianu Company Ltd | Transport & logistics | 2017 |
| Jiban Surbiton Ltd | Wholesale & retail | 2018 |
| Jimsbits Ltd | Wholesale & retail | 2024 |
| Jivda Limited | Information & communication | 2023 |
| JJ Kearney Limited | Information & communication | 2007 |
| JJ Maintenence Limited | Construction | 2025 |
| JJA3 Limited | Professional & scientific | 2020 |
| JJB Consulting (UK) Ltd | Professional & scientific | 2014 |
| JJM Communications Limited | Information & communication | 2017 |
| Jjos Consulting Limited | Professional & scientific | 2016 |
| JK Pursuit Ltd | Real estate | 2024 |
| JK Works Limited | Hospitality | 2012 |
| JKM Property Investments Ltd | Real estate | 2022 |
| Jla-Bb Enterprises Ltd | Wholesale & retail | 2025 |
| JLK Marketing Ltd | Professional & scientific | 2019 |
| JMD Resource Investment Limited | Financial services | 2016 |
| JMJ Venture Ltd | Real estate | 2023 |
| JMM Consult Limited | Professional & scientific | 2016 |
| Jmpa Ltd | Health & social care | 2024 |
| JND Cleaning Ltd | Administrative & support | 2021 |
| JO Cleaning Services Limited | Other services | 2019 |
| JOB Representation International Ltd | Professional & scientific | 2023 |
| Joeprocoffee Ltd | Manufacturing | 2023 |
| Joestar Marketing Ltd | Manufacturing | 2022 |
| John Holland and Associates Limited | Construction | 2003 |
| John LEE Meats Decorating & Building Services Ltd | Construction | 2020 |
| John Whelehan Psychological Services Ltd | Health & social care | 2025 |
| John Wilkinson Commodities Limited | Financial services | 1998 |
| Johnston and Family Holding Limited | Households | 2022 |
| Jollof Haven Nigeria Restaurant & Bar Limited | Hospitality | 2025 |
| Jolly Good Retail Ltd | Wholesale & retail | 2023 |
| JON O'Connor Broadcast Services Limited | Information & communication | 2013 |
| Jonah David Klein Limited | Information & communication | 2017 |
| Jonathon Lloyds Limited | Real estate | 2017 |
| Jones & Hogarth Properties Limited | Real estate | 2008 |
| Josamu Limited | Health & social care | 2018 |
| Journeaux Studio Limited | Construction | 2005 |
| Journey 52 Fitness Ltd | Extraterritorial | 2017 |
| Journeys of the Extraordinary Ltd | Information & communication | 2023 |
| Jo’S Spotless Solutions Ltd | Administrative & support | 2020 |
| JPM Estates Limited | Construction | 2016 |
| JPY Distribution Limited | Wholesale & retail | 2021 |
| JR Art Ltd | Financial services | 2020 |
| Jrrd Properties Ltd | Real estate | 2018 |
| JS Interests Ltd | Real estate | 2024 |
| JSR Digital Consulting Limited | Information & communication | 2024 |
| JSY Property Development Ltd | Construction | 2018 |
| JT Fleming Services Limited | Information & communication | 2018 |
| Jtcm Limited | Professional & scientific | 2022 |