| Invictus Energy (UK) Limited | Wholesale & retail | 2014 |
| Invistel Technology Solutions UK Limited | Information & communication | 2013 |
| Iouva Ltd | Information & communication | 2026 |
| Irepair Tech Limited | Wholesale & retail | 2025 |
| Iris Construction Ltd | Construction | 2019 |
| Iris Environmental Installations Ltd | Construction | 2022 |
| Irongate Management (Surbiton) Limited | Real estate | 2009 |
| Irvin Financial Services Limited | Financial services | 2013 |
| Isabella Nancy Limited | Wholesale & retail | 2023 |
| Isco Worldwide Limited | Professional & scientific | 2024 |
| Ishe E Limited | Health & social care | 2025 |
| Isla MAE Ltd | Public administration | 2024 |
| Island Coaches Limited | Transport & logistics | 2011 |
| Island Health Trust | Health & social care | 2008 |
| Island Leisure Products Limited | Manufacturing | 1999 |
| Isle of Bourne Cooling Ltd | Construction | 2025 |
| Isol Renatto Limited | Construction | 2019 |
| IT Star Tech Limited | Wholesale & retail | 2025 |
| Itechworx Limited | Administrative & support | 2023 |
| Itonlinelearning Ltd | Education | 2007 |
| IVY Cottage Farm Management Company Limited | Households | 1994 |
| Iwade Grill Ltd | Hospitality | 2026 |
| Iwade Mezze Grill Ltd | Hospitality | 2025 |
| Iwade Stores Ltd | Wholesale & retail | 2023 |
| Ixworth Consultancy Limited | Construction | 2013 |
| Izavé London Limited | Wholesale & retail | 2026 |
| Izra Cuisine Ltd | Hospitality | 2022 |
| IZU Logistics Ltd | Transport & logistics | 2024 |
| J & C Builders (South East) Ltd | Construction | 2005 |
| J & H Lettings Ltd | Real estate | 2016 |
| J & M Kapoor Properties Limited | Real estate | 2018 |
| J & O Soundbytes Ltd | Information & communication | 2011 |
| J & S Accountancy Ltd | Professional & scientific | 2012 |
| J Baker Developments Limited | Construction | 2004 |
| J Gomm Limited | Other services | 2007 |
| J Harvey Offshore Services Ltd | Mining & quarrying | 2018 |
| J J LEE Transport Limited | Transport & logistics | 2017 |
| J K Baxters Ltd | Construction | 2025 |
| J Mcgee Construction Ltd | Professional & scientific | 2013 |
| J N P Logistics Ltd | Transport & logistics | 2023 |
| J P Goodger Building Ltd | Construction | 2017 |
| J S C Property Developers Ltd | Real estate | 2023 |
| J Stewart Inspection Ltd | Professional & scientific | 2013 |
| J&C Events Group Ltd | Arts & recreation | 2022 |
| J&D Freight Services Ltd. | Transport & logistics | 2024 |
| J&H Roofing Limited | Construction | 2018 |
| J&K Property Investments Limited | Real estate | 2023 |
| J. a. M. Flooring Ltd | Construction | 2006 |
| J. Huang Limited | Administrative & support | 1997 |
| J.A.L. Decorators Limited | Construction | 2013 |
| J.Green Drylining Consultancy Limited | Construction | 2017 |
| J.M Jointing Ltd | Construction | 2023 |
| JAB Plumbing & Heating Ltd | Construction | 2015 |
| Jabeen's Kitchen Limited | Hospitality | 2018 |
| Jack Frost Creative Limited | Professional & scientific | 2012 |
| Jacobs Lodge Limited | Households | 2020 |
| Jacqueline Baldock Limited | Education | 2012 |
| Jade House NS Limited | Hospitality | 2026 |
| Jades Aesthetics Ltd | Other services | 2025 |
| Jadyrose Limited | Wholesale & retail | 2024 |
| Jaffri Ltd | Transport & logistics | 2021 |
| Jagged Barbers Ltd | Wholesale & retail | 2013 |
| Jaguar & Aston Specialists Limited | Wholesale & retail | 2007 |
| JAI Amba Mata 08 Limited | Wholesale & retail | 2026 |
| JAI MAA Shakti Limited | Professional & scientific | 2024 |
| JAI Shiv Holdings Ltd | Financial services | 2025 |
| Jaisvi Tech Ltd | Wholesale & retail | 2026 |
| JAM Partners Ltd | Wholesale & retail | 2026 |
| Jamber Construction Limited | Construction | 2020 |
| Jamber Managment Limited | Construction | 2018 |
| James Ainsworth Limited | Information & communication | 2016 |
| James Drake Catering Services Limited | Hospitality | 2023 |
| James Stevenson Heating and Plumbing Limited | Construction | 2016 |
| James W Bunce & Co Ltd | Professional & scientific | 2018 |
| Jamjar Housing Limited | Real estate | 2023 |
| Jane Okumu Limited | Health & social care | 2015 |
| Janp Traffic Management Limited | Construction | 2024 |
| JAR ENG Consultancy Limited | Professional & scientific | 2008 |
| Jarrett's Court Management Company Limited | Households | 1987 |
| Jarvis & Evans Brickwork Ltd | Construction | 2022 |
| Jarvis Residential Limited | Information & communication | 2022 |
| Jasnic Ltd | Other services | 2021 |
| Jason Burton Consulting Ltd | Professional & scientific | 2014 |
| Jasper Conrad Group Ltd. | Administrative & support | 2017 |
| Jaxsonbelle Group Ltd | Financial services | 2025 |
| JAY MAA Ltd | Other services | 2024 |
| Jaycrest Coaches Limited | Transport & logistics | 2014 |
| Jaymech Food Machines Limited | Manufacturing | 2015 |
| Jayspearl UK Ltd | Professional & scientific | 2014 |
| Jazz Pharmaceuticals Operations UK Limited | Manufacturing | 1999 |
| Jazz Pharmaceuticals Research UK Limited | Professional & scientific | 1995 |
| JB Landscape & Property Maintenance Ltd | Administrative & support | 2014 |
| JBS Commercial Vehicle Parts Limited | Wholesale & retail | 2023 |
| JBS Commercial Workshop Limited | Wholesale & retail | 2020 |
| JBS Haulage (Contractors) Limited | Transport & logistics | 2007 |
| JCC Mester Limited | Extraterritorial | 2011 |
| Jccm Solution Centre | Education | 2014 |
| JCR IT Services Ltd | Information & communication | 2016 |
| JD Facilities Solutions Ltd | Construction | 2026 |
| Jean Patrique Cookware Limited | Wholesale & retail | 2017 |