| IP Experts Ltd | Information & communication | 2007 |
| Iprint and Design Ltd | Manufacturing | 2011 |
| Isabelle Fielding Ltd | Professional & scientific | 2019 |
| ISB Consultancy Ltd | Information & communication | 2006 |
| Isolio Ltd | Information & communication | 2024 |
| Isolio Solutions Ltd | Information & communication | 2026 |
| Isopelle Limited | Information & communication | 2011 |
| Issy Bissy Ltd | Wholesale & retail | 2025 |
| IT Instructor Limited | Information & communication | 2026 |
| IT REC Limited | Professional & scientific | 2005 |
| Italia Family Limited | Administrative & support | 2020 |
| Itchy Wings Ltd | Transport & logistics | 2025 |
| Itsyourplace Lettings Ltd | Real estate | 2023 |
| Itsyourplace Limited | Households | 2006 |
| IVS Europe Limited | Wholesale & retail | 2014 |
| IX Systems Ltd | Professional & scientific | 2007 |
| Iyna Ltd | Information & communication | 2010 |
| J P Feltham Associates Ltd | Professional & scientific | 2016 |
| J Parkhouse Ltd | Financial services | 2019 |
| J&C Webster Group Limited | Real estate | 2025 |
| J&J Convenience Store Ltd | Wholesale & retail | 2022 |
| J&S Prestige Cars Ltd | Wholesale & retail | 2019 |
| J. a Campling Accounting Services Limited | Professional & scientific | 2012 |
| J.M.L. Henderson Limited | Wholesale & retail | 1973 |
| J4A Development Ltd | Administrative & support | 2003 |
| J4ZZ Consulting Limited | Information & communication | 2006 |
| J9CONSULTING (Management Services) Ltd | Professional & scientific | 2009 |
| JA Project Consulting Limited | Administrative & support | 2015 |
| Jackson Homestyle Developments Ltd | Real estate | 2015 |
| Jade Drive Ltd | Education | 2025 |
| Jamalo Limited | Professional & scientific | 2007 |
| JAY Shanti Care Limited | Health & social care | 2024 |
| Jaydd Limited | Education | 2016 |
| Jayweb Ltd | Information & communication | 2009 |
| JB8 Football Coaching Ltd | Education | 2025 |
| JC Bartlett Enterprises Ltd | Financial services | 2026 |
| JCC Consulting Services Limited | Administrative & support | 2016 |
| Jcpharma Ltd | Professional & scientific | 2024 |
| JD Horns Limited | Real estate | 2015 |
| JDR Hospitality Recruitment Limited | Administrative & support | 2012 |
| Jebson Consulting Ltd | Professional & scientific | 2018 |
| Jennett's Park (H18/H19) - Phase 2 Management Company Limited | Households | 2011 |
| Jennett's Park (H18/H19) Management Company Limited | Households | 2011 |
| Jennett's Park (H7) Management Company Limited | Households | 2008 |
| Jennetts Park H11 Management Company (Bracknell) Limited | Households | 2010 |
| Jennings Sound & Vision Ltd. | Wholesale & retail | 1996 |
| Jeremy Bates Consulting Ltd | Professional & scientific | 2019 |
| Jessett Consulting Limited | Information & communication | 2008 |
| JFB Fine Art Ltd | Arts & recreation | 2020 |
| JFK Plumbing and Heating Limited | Construction | 2002 |
| JFP Management Limited | Administrative & support | 2018 |
| JG FB Group Ltd | Wholesale & retail | 2021 |
| JGS Pizza Limited | Hospitality | 2008 |
| Jiminy Snippit Ltd | Other services | 2024 |
| JJW11 Ltd | Professional & scientific | 2023 |
| Jkab Accountancy Ltd | Professional & scientific | 2014 |
| JKL3 Limited | Construction | 2000 |
| Jlat Support Services Limited | Administrative & support | 2017 |
| JLC Fleet Limited | Real estate | 2016 |
| JLF Electrical Services Limited | Construction | 2002 |
| Jlilyfilms Ltd | Information & communication | 2024 |
| JMP Property Lettings Ltd | Real estate | 2024 |
| JMP Property Services Limited | Construction | 2015 |
| Jo's Neuro Coffee Ltd | Hospitality | 2026 |
| JOE Ralls Football Academy Ltd | Education | 2024 |
| John Kershaw Surveying Limited | Administrative & support | 2013 |
| John Russell Close Management Limited | Households | 2003 |
| John Russell Transport Planning Ltd | Professional & scientific | 2025 |
| Johnson House (Farnborough) RTM Company Ltd | Households | 2017 |
| Johnson Wealth Solutions Ltd | Financial services | 2025 |
| Jonnysvaletx Limited | Other services | 2025 |
| Jordan Brothers Bespoke Spaces Limited | Construction | 2022 |
| Joshmia Ltd | Real estate | 2017 |
| JP Fitness Limited | Arts & recreation | 2025 |
| Jpinto Holdings Limited | Financial services | 2024 |
| JR Corporation Ltd | Construction | 2023 |
| JR Digital Ltd | Wholesale & retail | 2011 |
| JRD Telecoms Consulting Ltd | Information & communication | 2021 |
| JRL Composites Ltd | Professional & scientific | 2024 |
| JS Mechanical Engineering Consultancy Limited | Professional & scientific | 2004 |
| JSC Electrical Contractors Ltd | Construction | 2017 |
| Jscr Holdings Limited | Financial services | 2025 |
| JSJ Executive Cars Ltd | Transport & logistics | 2024 |
| Juliet Liberda Physiotherapy Ltd | Health & social care | 2017 |
| Juliet Robson Design Ltd | Wholesale & retail | 2021 |
| Junglemania Adventure Golf Ltd | Arts & recreation | 2018 |
| Junior Self Defence Ltd | Arts & recreation | 2015 |
| Just Cars 4U Ltd | Wholesale & retail | 2019 |
| Just Flat Whites Ltd | Hospitality | 2026 |
| Justice Sector Consulting Limited | Public administration | 2017 |
| JV & Sons Limited | Wholesale & retail | 2016 |
| JV Trend Services Ltd | Information & communication | 2025 |
| JWL Consultants Limited | Professional & scientific | 2017 |
| Jwlh Enterprises Limited | Wholesale & retail | 2025 |
| JWS FOX Ltd | Extraterritorial | 2024 |
| K J Building Services Limited | Construction | 1997 |
| KAM3 Limited | Professional & scientific | 2018 |
| KAN Consulting Ltd | Professional & scientific | 2022 |
| Kanehr Limited | Administrative & support | 2024 |
| Karrabee Limited | Professional & scientific | 2015 |