| JJ Mcginley Limited | Real estate | 2016 |
| JJ Style Limited | Real estate | 2024 |
| JJ Supplements Limited | Wholesale & retail | 2025 |
| JJ Windows Ltd | Administrative & support | 2023 |
| JJ888 Property Limited | Real estate | 2017 |
| Jjbk Limited | Real estate | 2016 |
| JJC (London) Ltd | Construction | 2018 |
| JJF Coding Limited | Public administration | 2015 |
| JJG Projects Ltd | Professional & scientific | 2021 |
| Jjhe Commerce Limited | Wholesale & retail | 2025 |
| JJJ OD Ltd | Financial services | 2023 |
| Jjxg Logistic Ltd | Transport & logistics | 2024 |
| JK Engineering (Hertfordshire) Limited | Manufacturing | 2007 |
| JK Engineering (Holdings) Limited | Professional & scientific | 2009 |
| JK Hub Ltd | Wholesale & retail | 2026 |
| JK Inspiration Ltd | Construction | 2022 |
| JK Oguns Ltd | Information & communication | 2016 |
| JK Post Ltd | Wholesale & retail | 2021 |
| JK Prime Ltd | Hospitality | 2020 |
| JK Tyre Masters Ltd | Wholesale & retail | 2024 |
| JKA Building Services Limited | Construction | 2018 |
| Jkay Consultancy Ltd | Information & communication | 2022 |
| JKC Lawyers LLP | | 2012 |
| JKD IT Limited | Information & communication | 2025 |
| Jkrk Holdings Limited | Financial services | 2026 |
| JKW Property Group Limited | Construction | 2020 |
| JL PCO Limited | Information & communication | 2026 |
| JL Trans Limited | Other services | 2026 |
| JLB Associates Limited | Real estate | 1997 |
| JLC Creative Limited | Administrative & support | 2017 |
| JLE Data Analytic Solutions Ltd | Information & communication | 2024 |
| JLG Sales Ltd | Wholesale & retail | 2025 |
| Jlgame Limited | Wholesale & retail | 2021 |
| Jluxelondon Limited | Wholesale & retail | 2019 |
| JLY Consultancy Ltd | Administrative & support | 2016 |
| JM 14 Ltd | Real estate | 2022 |
| JM Interact Ltd | Information & communication | 2019 |
| JMB Marketing Services Ltd | Professional & scientific | 2019 |
| JMC Property Holdings Limited | Real estate | 2019 |
| JME Heights Ltd | Real estate | 2024 |
| JMF Tuning Limited | Wholesale & retail | 2024 |
| JMN Welding Services Ltd | Manufacturing | 2022 |
| JMT Consulting Ltd | Agriculture & fishing | 2013 |
| JMW Worldwide Ltd | Professional & scientific | 2020 |
| JN IT Solutions Limited | Information & communication | 2015 |
| JNC Financial Services Limited | Professional & scientific | 2023 |
| Jnkl Services Ltd | Professional & scientific | 2023 |
| JNO. Croad Limited | Professional & scientific | 1928 |
| JNR Events Ltd | Administrative & support | 2025 |
| Jnre Investments Limited | Real estate | 2024 |
| Jnslee Ltd | Real estate | 2022 |
| Jo'Burg Ltd | Real estate | 2024 |
| Joal Limited | Professional & scientific | 2015 |
| Joanna Pratt Consulting Ltd | Professional & scientific | 2022 |
| JOB Match HR Ltd | Administrative & support | 2025 |
| Jobak Limited | Health & social care | 2016 |
| Jocasta Anderson Ltd | Information & communication | 2019 |
| Jodi Pyle Limited | Financial services | 2017 |
| JOE Inniss Consulting Ltd | Professional & scientific | 2019 |
| Joe's Fish and Chips Ltd | Wholesale & retail | 2019 |
| Joe's Gourmet Foods International Limited | Manufacturing | 2026 |
| Joel Farm Inc Ltd | Real estate | 2019 |
| Joel Street Restaurant Ltd | Hospitality | 2023 |
| John Builder Contractor Ltd | Transport & logistics | 2023 |
| John Day Rentals Limited | Households | 2025 |
| John DOE Limited | Real estate | 1995 |
| John Harris & Partners Ltd | Professional & scientific | 2025 |
| John Jones(Excavation)Limited | Construction | 1967 |
| John Joseph Limited | Real estate | 2000 |
| John Mitchell Fine Paintings Ltd | Wholesale & retail | 2015 |
| John Rennison Limited | Financial services | 2016 |
| John Watson and Carter Limited | Professional & scientific | 2006 |
| John Whiteman & Co LLP | | 2010 |
| Johnny Gurkha Services Limited | Extraterritorial | 2009 |
| Joie Capital Limited | Professional & scientific | 2023 |
| Jojoba Cosmetics Limited | Wholesale & retail | 2009 |
| Jolec Electrical Supplies Limited | Administrative & support | 2015 |
| Jolly&Johnson Limited | Health & social care | 2014 |
| Jonasky’S Detailing Ltd | Administrative & support | 2026 |
| Jony Opportunity Ltd | Construction | 2017 |
| Jonze Artz Limited | Arts & recreation | 2011 |
| Jordan Mayo Advisory Limited | Professional & scientific | 2024 |
| Joria Construction Services Ltd | Construction | 2024 |
| Joseph Court Management Company Limited | Households | 2006 |
| Joseph Darcy Ltd | Wholesale & retail | 2018 |
| Joseph Moran Media Ltd | Information & communication | 2024 |
| Josephine Samson Ltd | Information & communication | 2026 |
| Josh Construct Limited | Construction | 2023 |
| Joshee Foods Ltd | Wholesale & retail | 2022 |
| Joshpharm Limited | Wholesale & retail | 2008 |
| Joshua Hills Nutrition Ltd | Education | 2024 |
| Josimes Limited | Education | 2018 |
| Joss Herd Limited | Hospitality | 2014 |
| Joss IT Solutions Limited | Information & communication | 2012 |
| Jots Electrics Limited | Construction | 2014 |
| Journey to Wealth CIC | Other services | 2025 |
| Journeyman Productions Ltd | Arts & recreation | 2026 |
| Jowettyorke Painting and Interiors Ltd | Construction | 2025 |
| Joy in Golf II Limited | Arts & recreation | 2016 |
| Joy in Golf Limited | Arts & recreation | 2016 |