| Issarcoaches Limited | Transport & logistics | 2015 |
| IT Service Consultancy Ltd | Information & communication | 2019 |
| Itbt Limited | Wholesale & retail | 2020 |
| ITC Global (UK) Limited | Information & communication | 2014 |
| ITE Delivery Ltd | Information & communication | 2023 |
| Iterroni Cafe Limited | Hospitality | 2025 |
| Itswho Limited | Information & communication | 2014 |
| J & G Transport Services Limited | Manufacturing | 2025 |
| J Brock Solution Ltd | Information & communication | 2022 |
| J C Buchanan Building Services Ltd | Construction | 2008 |
| J Corp Limited | Information & communication | 2009 |
| J L Norman Ltd | Real estate | 2013 |
| J R Binkowski Ltd | Transport & logistics | 2018 |
| J R D (UK) Limited | Wholesale & retail | 2004 |
| J T Properties Limited | Real estate | 2012 |
| J Wenman Services Ltd | Construction | 2025 |
| J, S & J Meares Limited | Households | 2022 |
| J-Eco Ltd | Administrative & support | 2024 |
| J. & J. Topgrade Limited | Administrative & support | 1984 |
| J. Wallis Consulting Limited | Other services | 2007 |
| J.R GAS Works Ltd | Professional & scientific | 2025 |
| J2AO Developments Ltd | Construction | 2024 |
| Jacey and Aruna Limited | Financial services | 2021 |
| Jacinth Ventures (UK) Limited | Construction | 2013 |
| Jaco Fish and Chips Ltd | Hospitality | 2024 |
| Jafland Ltd | Wholesale & retail | 2026 |
| JAG Gill Consultants (UK) Limited | Wholesale & retail | 2016 |
| JAI Bhagwati Technologies Ltd | Information & communication | 2022 |
| Jalmeza Houses Ltd | Real estate | 2022 |
| James Hannah Limited | Information & communication | 2014 |
| Jamm Ventures Ltd | Agriculture & fishing | 2025 |
| Janvas Limited | Information & communication | 2025 |
| Japanese Imports Limited | Wholesale & retail | 2025 |
| Jasem Ltd | Construction | 2025 |
| Jash Infra Ltd | Real estate | 2019 |
| Jaskaran Singh Ltd | Construction | 2023 |
| Jasna Properties Ltd | Real estate | 2025 |
| Jasper Services Limited | Professional & scientific | 2019 |
| Jawcoecom Ltd | Information & communication | 2025 |
| Jaycee Electrical Ltd | Construction | 2022 |
| Jays Removals Ltd | Transport & logistics | 2018 |
| JB Jointing Solutions Limited | Construction | 2024 |
| JB Leisure Consultancy Limited | Administrative & support | 2020 |
| JB Sales & Promotions Limited | Other services | 2018 |
| JBW Productions Ltd | Professional & scientific | 2022 |
| JCL DG Training Ltd | Administrative & support | 2021 |
| Jcmd Property Management Ltd | Real estate | 2020 |
| JCW Property Group Ltd | Real estate | 2023 |
| JD Contractors and Construction Services Limited | Construction | 2024 |
| JDL Environmental Engineering Offshore Ltd | Professional & scientific | 2020 |
| Jdls Interiors LLP | | 2019 |
| Jdpw Investments Ltd | Real estate | 2019 |
| Jdtfl Consultants Limited | Professional & scientific | 2014 |
| Jenko.Cc Limited | Wholesale & retail | 2021 |
| JET Star Carriers Ltd | Transport & logistics | 2013 |
| Jetline Aviator Ltd | Administrative & support | 2026 |
| JFD Associates Ltd | Construction | 2005 |
| JG Services (P) Ltd | Real estate | 2025 |
| JJE Enterprises Ltd | Wholesale & retail | 2009 |
| JJG Estates Ltd | Households | 2019 |
| Jjigs Trading Limited | Wholesale & retail | 2017 |
| Jkny Limited | Real estate | 2022 |
| JKS Thames Ltd | Real estate | 2023 |
| JM Horticulture Limited | Professional & scientific | 2019 |
| JMC Hydraulics Ltd | Professional & scientific | 2009 |
| JMS Used Cars Ltd | Wholesale & retail | 2022 |
| Jnkm Property Ltd | Real estate | 2024 |
| JNY Storage Limited | Transport & logistics | 2020 |
| JOE Bench Props Ltd | Professional & scientific | 2023 |
| John&Jessy Limited | Real estate | 2022 |
| Johnlee Pharmaceuticals Ltd | Wholesale & retail | 2025 |
| Johnson Smith & Co Ltd | Professional & scientific | 2000 |
| Jointedge Property Limited | Real estate | 2026 |
| Jolik Services Ltd | Information & communication | 2025 |
| Jolu Ltd | Arts & recreation | 2019 |
| Jomar Mechanical Services Limited | Construction | 2021 |
| Jonathan Darnell Engineering Limited | Professional & scientific | 2020 |
| Jones Tiling Limited | Construction | 2019 |
| Joppa Financial Services Limited | Financial services | 2020 |
| JP Regal Assets Ltd | Real estate | 2026 |
| Jp's Handy Services Ltd | Construction | 2025 |
| JP70 Limited | Transport & logistics | 2023 |
| JPE Services Ltd | Information & communication | 2026 |
| JR Square Transport Ltd | Construction | 2023 |
| JRG Developments Limited | Real estate | 2018 |
| JRM Haulage Ltd | Transport & logistics | 2021 |
| JSJ Flooring Commercial Limited | Construction | 2026 |
| Jslg Ltd | Wholesale & retail | 2023 |
| Jsnc Limited | Construction | 2019 |
| JSS Carpentry and Construction Ltd | Construction | 2025 |
| JSW Creations Ltd | Wholesale & retail | 2023 |
| Judo Learning Pathways Ltd | Arts & recreation | 2026 |
| Jukawa Ltd | Extraterritorial | 2023 |
| Julia Hughes Limited | Health & social care | 2007 |
| Julia K Brownlie Accounting Services Limited | Professional & scientific | 2016 |
| Juniper Solutions Limited | Wholesale & retail | 2024 |
| Just EGG (Chilled Foods) Limited | Manufacturing | 2002 |
| Just Toys Limited | Wholesale & retail | 2024 |
| K & Co Accountants Ltd | Professional & scientific | 2026 |
| K & J Staines Ltd | Wholesale & retail | 2016 |