| Jefel Ltd | Hospitality | 2015 |
| Jefferies London Ltd | Real estate | 2025 |
| Jefferies London Prime Real Estate Limited | Real estate | 2021 |
| Jeli Films Ltd | Information & communication | 2012 |
| Jelshaker Ltd. | Health & social care | 2023 |
| JEM Property Solutions Ltd | Administrative & support | 2013 |
| JEMY4 Properties Ltd | Households | 2024 |
| Jenerate Ltd | Information & communication | 2010 |
| Jersey Export Limited | Wholesale & retail | 2024 |
| Jestel Software Ltd | Information & communication | 2008 |
| Jesus IS Lord Global UK C.I.C. | Other services | 2023 |
| JET Stream ADS Limited | Information & communication | 2019 |
| Jewellery by AA Limited | Wholesale & retail | 2019 |
| JGM Motor Trading Limited | Wholesale & retail | 2025 |
| JH Paraplanners Limited | Administrative & support | 2015 |
| JH Wine Merchants Limited | Wholesale & retail | 2020 |
| Jhaveri Futuregen Limited | Health & social care | 2019 |
| JI Transport Solutions Limited | Wholesale & retail | 2025 |
| Jide Ltd | Wholesale & retail | 2010 |
| JIH Consulting Limited | Health & social care | 2017 |
| Jiji Cleaning Services Limited | Administrative & support | 2023 |
| Jikam Ltd | Health & social care | 2022 |
| JIM at Tea Cosy Ltd | Hospitality | 2016 |
| JIU Jitsu East Bristol Ltd | Education | 2023 |
| JIU Jitsu Inspires CIC | Other services | 2022 |
| JJE Consulting Ltd | Professional & scientific | 2026 |
| JJP Consultancy Limited | Professional & scientific | 2015 |
| JJR Spares & Parts Ltd | Wholesale & retail | 2025 |
| Jj’S Plaice Ltd | Hospitality | 2022 |
| JK Asset Management Ltd | Information & communication | 2014 |
| JK Rigging Limited | Information & communication | 2009 |
| Jkbg Limited | Real estate | 2024 |
| Jkbnanny Limited | Education | 2024 |
| Jkjk UK Ltd | Transport & logistics | 2009 |
| JKO Konsultancy Ltd | Professional & scientific | 2017 |
| JLC Commercial Property Ltd | Real estate | 2021 |
| JLC Properties & Lettings Ltd. | Real estate | 2016 |
| JLE Business Consulting Limited | Professional & scientific | 2010 |
| JLG Ventures Ltd | Construction | 2015 |
| JLW Limited | Arts & recreation | 2015 |
| JM Associated Ltd | Information & communication | 2018 |
| JM Beauty Salon Ltd | Other services | 2020 |
| JM Display Ltd | Manufacturing | 2020 |
| JM Fernando Ltd | Professional & scientific | 2009 |
| JM House Limited | Real estate | 2022 |
| JM Paint Ltd | Arts & recreation | 2024 |
| JM Stokes Decorators Limited | Administrative & support | 2006 |
| Jm-Dm Services Ltd | Professional & scientific | 2025 |
| JMA Ltd | Professional & scientific | 2018 |
| Jman & OMF Services Limited | Health & social care | 2025 |
| JMJ Radiology Ltd | Health & social care | 2022 |
| Jmjll Holdings Limited | Financial services | 2025 |
| Jmjlt Holdings Limited | Financial services | 2019 |
| JMK Rigging Ltd | Other services | 2009 |
| JML Services Limited | Construction | 2015 |
| JML Window Repairs Limited | Construction | 2026 |
| Jmte Brickworks Ltd | Construction | 2016 |
| JN Holdco Limited | Financial services | 2025 |
| Jnimports Limited | Wholesale & retail | 2011 |
| Jnjazz Limited | Real estate | 2024 |
| Jnlettings Limited | Real estate | 2017 |
| JNR Trading Group Ltd | Hospitality | 2020 |
| JNS Consulting Limited | Health & social care | 2017 |
| JO Fewell Travel Ltd | Administrative & support | 2025 |
| JO TV Limited | Information & communication | 2006 |
| JO Warner Ltd | Health & social care | 2021 |
| Joanna Claire Aesthetics Clinic Ltd | Other services | 2026 |
| Joanna Smith Limited | Information & communication | 2019 |
| Joas (Self Assessments) Limited | Professional & scientific | 2018 |
| Jobey Limited | Arts & recreation | 2017 |
| Joblin Contracts Limited | Construction | 2020 |
| Jobling Quantity Surveying Ltd | Professional & scientific | 2021 |
| Jocaz Vantage Ltd | Other services | 2024 |
| Joejack Consulting Limited | Information & communication | 2025 |
| John B Ltd | Construction | 2024 |
| John Barnes Legal Services Limited | Professional & scientific | 2010 |
| John Boyle Construction Ltd | Construction | 2015 |
| John Empson Flooring Contractors Limited | | 1989 |
| John Gordon Motors Limited | Wholesale & retail | 1978 |
| John Mooney Audio Ltd | Arts & recreation | 2004 |
| John Wallis Walls Limited | Extraterritorial | 2011 |
| Johnny Sins Ltd | Manufacturing | 2025 |
| Johnson Property Services Ltd | Real estate | 2024 |
| Johny Tiling Ltd | Construction | 2020 |
| Jollof Paste Ltd | Manufacturing | 2023 |
| Jolly British Developments Limited | Construction | 2019 |
| Jonathan Maris Limited | Arts & recreation | 2002 |
| Jones & Bones Engineering Limited | Professional & scientific | 2014 |
| Jones Baker Engineering Ltd | Professional & scientific | 2012 |
| Jones Property Holdings Limited | Real estate | 2017 |
| Jontidd Property Ltd | Real estate | 2020 |
| Jorgyogarajah Ltd | Administrative & support | 2026 |
| Josafat Care Services Ltd | Health & social care | 2025 |
| Joshali Limited | Health & social care | 2022 |
| Joslinc Investments Limited | Wholesale & retail | 2013 |
| Jovon Hearing Limited | Health & social care | 2009 |
| Joy Caring Services Ltd | Administrative & support | 2013 |
| Joy of Many Generations Ltd | Information & communication | 2024 |
| Jpdsw Ltd | Administrative & support | 2025 |
| JPE Consultants Ltd | Professional & scientific | 2025 |