| J L W Rigging Ltd | Information & communication | 2015 |
| J Patterson Properties Ltd | Real estate | 2022 |
| J Patterson Tutors Ltd | Education | 2022 |
| J Sparkz Ltd | Construction | 2023 |
| J Xxiii Ltd | Construction | 2023 |
| J&D Property Group Ltd | Real estate | 2026 |
| J&G Connections Ltd | Construction | 2020 |
| J&L Renovation Ltd | Construction | 2023 |
| J&R Contracting Group Ltd | Construction | 2016 |
| J. Burnage Properties Ltd | Real estate | 2020 |
| J. Soteriou Properties Ltd | Real estate | 2023 |
| J.A.S - JAS Accounting Services Ltd | Professional & scientific | 2014 |
| J.Cohen Property Consultant Ltd | Real estate | 2022 |
| J.O.L. Construction Ltd | Construction | 2010 |
| J.Spencer Farriery Ltd | Administrative & support | 2025 |
| J.W.Chant & Co Limited | Extraterritorial | 2017 |
| JA Connelly Limited | Information & communication | 2017 |
| JA Smart & Fast Ltd | Construction | 2023 |
| JAC Property Management Limited | Real estate | 2020 |
| Jack the Chipper Greenwich Ltd | Hospitality | 2023 |
| Jackpot Capital Ltd | Hospitality | 2026 |
| Jade Stone Artwork Ltd | Arts & recreation | 2024 |
| Jaguar Bidco Limited | Financial services | 2018 |
| Jaguar Holdco Limited | Financial services | 2018 |
| Jaguar Midco Limited | Financial services | 2018 |
| Jaguar Topco Limited | Financial services | 2018 |
| Janset & Sude Property Limited | Real estate | 2020 |
| Jarc’Y Cosmetics Ltd | Wholesale & retail | 2024 |
| JB Construction & Electrical Ltd | Construction | 2021 |
| JC and Sons Property Maintenance Ltd | Households | 2022 |
| JC Fire Solutions Ltd | Construction | 2024 |
| JC Plumbing and GAS Services Ltd | Construction | 2022 |
| Jcmls Limited | Information & communication | 2011 |
| JCS Firesafe Limited | Construction | 2017 |
| Jdkp Properties Limited | Real estate | 2022 |
| JED Fitness Ltd | Education | 2023 |
| Jennifer Rose Consulting Ltd | Professional & scientific | 2018 |
| Jens DEN Child Care Services Ltd | Health & social care | 2014 |
| Jeremias Morandell Limited | Administrative & support | 2015 |
| JET & Sons Properties Limited | Real estate | 2019 |
| Jetenterprises UK Limited | Information & communication | 2003 |
| JFX Trading Limited | Financial services | 2010 |
| JHA Plumbing Ltd | Construction | 2018 |
| JHC Media 96 Ltd | Information & communication | 2025 |
| JHS Marios Grill Limited | Hospitality | 2025 |
| Jimmy Gardens Ltd | Administrative & support | 2025 |
| Jimmy Greenwork Ltd | Administrative & support | 2025 |
| JJ Landscapes Creations Ltd | Administrative & support | 2025 |
| JJ Properties Investment Ltd | Real estate | 2026 |
| JJ4U Accounting Solutions Ltd | Professional & scientific | 2023 |
| JJD Bookkeeping Services Limited | Professional & scientific | 2010 |
| JLH Windows Ltd | Wholesale & retail | 2025 |
| JLO Property Limited | Construction | 2015 |
| Jloose Ltd | Construction | 2023 |
| JM Building Limited | Construction | 2005 |
| JM Design Associates Ltd | Professional & scientific | 2016 |
| Jmac Global Holdings Limited | Other services | 2018 |
| JMD 74 Management Ltd | Other services | 2018 |
| JME Coaching Limited | Education | 2024 |
| JNK Divine Ltd | Health & social care | 2024 |
| JNS Sparkles Cleaning Services Ltd | Administrative & support | 2020 |
| JO Connelly Limited | Professional & scientific | 2014 |
| Jockey Inn Ltd | Hospitality | 2020 |
| JOE Clarke Limited | Arts & recreation | 2016 |
| JOE James Limited | Wholesale & retail | 2023 |
| JOE Swanson Limited | Information & communication | 2014 |
| Joemms Limited | Health & social care | 2024 |
| John Simpson Racing Limited | Arts & recreation | 2014 |
| Johnson Islandwide Imports Ltd | Wholesale & retail | 2020 |
| Jojo's Foods London Ltd | Hospitality | 2024 |
| Jollyes Group Limited | Financial services | 2007 |
| Jollyes Retail Group Limited | Financial services | 2011 |
| Jopadhola Community UK CIC | Health & social care | 2020 |
| Jordscape Technologies Limited | Information & communication | 2020 |
| Joseph David Limited | Hospitality | 2024 |
| Joss Films Ltd | Arts & recreation | 2008 |
| JP Ortho Ltd | Health & social care | 2024 |
| JPS Plumbing & GAS Ltd | Construction | 2013 |
| JR Yard Rentals Ltd | Financial services | 2023 |
| JRK Building Services Ltd | Construction | 2011 |
| JS42 Ltd | Administrative & support | 2022 |
| JSC80 Stores Ltd | Wholesale & retail | 2022 |
| JSH Media Ltd | Professional & scientific | 2025 |
| JSR Automotive Ltd | Wholesale & retail | 2025 |
| JT Sports Partners Ltd | Arts & recreation | 2022 |
| JTC Cleaning Services Ltd | Administrative & support | 2024 |
| Judi Kingsley Creative Ltd | Arts & recreation | 2023 |
| July 7 Consulting Ltd | Hospitality | 2023 |
| Junk.Movers London Ltd | Water & waste | 2025 |
| Just a Group Limited | Administrative & support | 2019 |
| Just NOW Distribution Limited | Wholesale & retail | 2023 |
| Just Nurses Limited | Health & social care | 2014 |
| Just OT Limited | Health & social care | 2013 |
| Just SO Care Ltd | Manufacturing | 2020 |
| Justgp Limited | Health & social care | 2015 |
| Justphysio Limited | Health & social care | 2011 |
| JWP Electrical Services Limited | Construction | 2026 |
| JZ Consultant Group Ltd | Information & communication | 2025 |
| JZ Recruitment Limited | Administrative & support | 2021 |
| K & P Investments Ltd | Construction | 2018 |