| J Busby Insight & Send Solutions Ltd | Information & communication | 2026 |
| J E Hughes Builders Limited | Construction | 2018 |
| J Gyimah Management Limited | Information & communication | 2022 |
| J T Stonework & Restoration Limited | Construction | 2007 |
| J'3 Business Ventures Ltd | Health & social care | 2014 |
| J. O.E Zion Ltd | Wholesale & retail | 2020 |
| J.D Cook Heating Services Ltd | Construction | 2024 |
| J.U. Parcelpro & Service Ltd | Transport & logistics | 2024 |
| Jaanavi Properties Ltd | Real estate | 2021 |
| Jaap Actuarial Limited | Financial services | 2022 |
| Jack of ALL Trades - Joat Ltd | Construction | 2026 |
| Jackson Property London Ltd | Households | 2021 |
| Jacqueline's Gems Childcare Services Ltd | Health & social care | 2014 |
| Jakes Engineering Limited | Wholesale & retail | 2020 |
| Jaklans Incorporated Limited | Professional & scientific | 2015 |
| James G Taylor Ltd | Other services | 2025 |
| Jamores Limited | Professional & scientific | 2009 |
| Janama Consultancy Limited | Information & communication | 2016 |
| Jandi Ventures (UK) Limited | Manufacturing | 2008 |
| Janeyrb Properties Limited | Households | 2022 |
| JAS Housing Ltd | Real estate | 2025 |
| Jasmine Doidge Limited | Real estate | 2019 |
| JAW Solutions Ltd | Professional & scientific | 2025 |
| JAX BM Ltd | Construction | 2014 |
| JAY Properties Services Limited | Real estate | 2023 |
| JAY SQ Cares Limited | Health & social care | 2019 |
| Jay-Coker Consulting Ltd | Administrative & support | 2014 |
| Jaynae Ltd | Extraterritorial | 2020 |
| Jbear Ltd | Hospitality | 2019 |
| JBM Security Ltd | Administrative & support | 2018 |
| JBS Ventures Ltd | Professional & scientific | 2013 |
| Jc&Ce Wright Consultancy Ltd | Administrative & support | 2021 |
| Jccmi Properties Limited | Professional & scientific | 2012 |
| JDP Installations Ltd | Construction | 2021 |
| Jedna Ltd | Real estate | 2024 |
| Jehovah Mercy Temple C&S Church | Other services | 2013 |
| Jelly Music International Limited | Arts & recreation | 2026 |
| Jennings & Kent Limited | Other services | 1994 |
| Jercare Services Limited | Health & social care | 2019 |
| Jeremy Wynne Ltd | Professional & scientific | 2014 |
| Jerkyn Caribbean Spice Ltd | Hospitality | 2024 |
| Jermaine Johnson-Douglas Limited | Construction | 2018 |
| Jesse Consultancy Ltd | Health & social care | 2022 |
| Jetglo Limited | Hospitality | 2010 |
| JHB Chauffeurs Ltd | Transport & logistics | 2020 |
| Jibzconnect Ltd | Real estate | 2025 |
| JIL Nectar Limited | Transport & logistics | 2014 |
| Jimbee Healthcare Ltd | Health & social care | 2019 |
| Jimit Limited | Other services | 2018 |
| JJJ Export Ltd | Wholesale & retail | 2025 |
| JK Dryling Ltd | Construction | 2022 |
| JK Social Care Limited | Health & social care | 2022 |
| JKB Shine (UK) Limited | Financial services | 2018 |
| JKJ Consultants Limited | Professional & scientific | 2015 |
| Jkse Limited | Real estate | 2026 |
| JLR Cleaning & Maintenance Ltd | Administrative & support | 2025 |
| JM Medical Healthcare Ltd | Health & social care | 2026 |
| JMS Group Properties Ltd | Real estate | 2017 |
| JO Informatics Limited | Information & communication | 2009 |
| Joaatservices Ltd | Health & social care | 2022 |
| Job-Track Employment Solutions Ltd | Administrative & support | 2013 |
| JOE Felix Sports Ltd | Administrative & support | 2013 |
| Joelouise Property Ltd | Real estate | 2025 |
| Joha Jewellery Ltd | Wholesale & retail | 2024 |
| John Patrick Equity Limited | Real estate | 2021 |
| Johnokuns Limited | Health & social care | 2020 |
| Johnsonsmanagement Ltd | Real estate | 2019 |
| Johntosin Limited | Financial services | 2014 |
| Jojovmagnifique Limited | Health & social care | 2019 |
| Jonathanmaccarthy Ltd | Administrative & support | 2020 |
| Jones Brothers and Sons Ltd | Real estate | 2025 |
| Jony UK Limited | Administrative & support | 2018 |
| Jool London Ltd | Wholesale & retail | 2024 |
| Jopnah's Limited | Wholesale & retail | 2023 |
| Jordan Dicks Design Ltd | Professional & scientific | 2020 |
| Josh & Co Properties Ltd | Other services | 2021 |
| Joy Childminder Services Limited | Other services | 2019 |
| Joy of Sound (JOS) | Health & social care | 2007 |
| Joyfest Ventures Limited | Real estate | 2023 |
| JP & RON Ltd | Real estate | 2014 |
| JR Landmark Ltd | Real estate | 2025 |
| JRK Accountancy Services Limited | Professional & scientific | 2008 |
| JS CONSTRUCTION20 Ltd | Construction | 2025 |
| JS International Solution Ltd | Other services | 2025 |
| JSC Property Services Ltd | Construction | 2026 |
| Jsis Limited | Extraterritorial | 2004 |
| JST Entertainment Limited | Administrative & support | 2016 |
| JT Roofing(Kent) Ltd | Construction | 2019 |
| JT Zinc Roofing and Cladding Ltd | Construction | 2022 |
| JTA Consultancy Ltd | Professional & scientific | 2024 |
| JUC Consultancy Ltd | Professional & scientific | 2013 |
| Julian James & Sons Limited | Construction | 2014 |
| Julius Akpoudje Limited | Transport & logistics | 2020 |
| Jung Pumpen Ltd | Manufacturing | 2013 |
| Just Record Limited | Information & communication | 2019 |
| Justin SP Solutions Limited | Information & communication | 2018 |
| Juw-An Limited | Professional & scientific | 2014 |
| Juw-An Services Limited | Financial services | 2015 |
| Jwaao Business Limited | Wholesale & retail | 2025 |
| K a D Facilities Limited | Real estate | 2018 |