| Iskay Partners Ltd | Real estate | 2025 |
| Isleoak Consultants Limited | Information & communication | 2001 |
| Islogical Ltd | Information & communication | 2019 |
| Istanbul Barbers (Lancaster) Ltd | Other services | 2024 |
| It's a Kind of Magic Dance Events Limited | Arts & recreation | 2024 |
| Itwiser Comms Ltd | Information & communication | 2014 |
| Itwiser LLP | | 2007 |
| Ivar Properties Limited | Real estate | 2024 |
| Iway Design and Development Ltd | Information & communication | 2018 |
| IWS Consulting Ltd | Information & communication | 2020 |
| Iyngarans Ltd | Hospitality | 2022 |
| J & M Leisure Parks Limited | Hospitality | 2017 |
| J & M Sheet Metal Limited | Manufacturing | 2003 |
| J & P Care Services Limited | Extraterritorial | 2013 |
| J Basi DO Limited | Professional & scientific | 2024 |
| J Burr Contracting Limited | Agriculture & fishing | 2020 |
| J Burrow Electrical Limited | Construction | 2025 |
| J C Organic Services Ltd | Professional & scientific | 2025 |
| J D Gallagher Estate Agents Limited | Real estate | 2000 |
| J Earl Limited | Construction | 2023 |
| J G S Cladding and Roofing Limited | Construction | 2023 |
| J Greenwood Limited | Agriculture & fishing | 2008 |
| J H Lowson & Company Limited | Financial services | 2012 |
| J J Mcqueen Limited | Construction | 2002 |
| J Kelly Investments Limited | Real estate | 2024 |
| J L Lofthouse & SON Limited | Construction | 2011 |
| J M T & N Ltd | Real estate | 2017 |
| J P Kummer Holdings Limited | Professional & scientific | 2013 |
| J P Rigby Limited | Construction | 2024 |
| J P Wright & Sons Ltd | Construction | 2019 |
| J R G Mason | Agriculture & fishing | 2020 |
| J Recruitment Ltd | Administrative & support | 2022 |
| J S Close Holdings Limited | Financial services | 2017 |
| J W Asbestos & Demolition Limited | Construction | 2015 |
| J Williams Consultancy Ltd | Administrative & support | 2017 |
| J&A Herd Limited | Wholesale & retail | 2013 |
| J&G Hospitality Ltd | Hospitality | 2025 |
| J&Son Park Ltd | Hospitality | 2024 |
| J. Atkinson & Co. (Lancaster) Limited | Wholesale & retail | 2005 |
| J. Parkinson & Sons (Contracting) Limited | Wholesale & retail | 1980 |
| J.A. Mount Limited | Construction | 2003 |
| J.D.S. Interiors Limited | Construction | 2000 |
| J.S Close Limited | Manufacturing | 1985 |
| J.S. Andrews & Co. Ltd | Professional & scientific | 1999 |
| J2L Business Solutions Ltd | Professional & scientific | 2021 |
| J2M Limited | Professional & scientific | 2008 |
| JA Hester Limited | Wholesale & retail | 2005 |
| JAB Lettings Ltd | Real estate | 2025 |
| Jack Senior Limited | Administrative & support | 2019 |
| Jack-A-Bite Limited | Hospitality | 2024 |
| Jackrose Consulting Limited | Financial services | 2022 |
| JAM Property Co Ltd | Real estate | 2021 |
| James Brockbank Ltd | Information & communication | 2014 |
| James Cogan Solutions Limited | Wholesale & retail | 2020 |
| James Croker Ltd | Transport & logistics | 2026 |
| James Hospitality Ltd | Hospitality | 2024 |
| James Parker Construction Ltd | Administrative & support | 2024 |
| James Woodhouse Ltd | Information & communication | 2023 |
| JAN Bell Property Limited | Real estate | 2025 |
| JAN Kent Hair Limited | Other services | 2013 |
| Jane Samson Ltd | Professional & scientific | 2024 |
| JAR Architecture Ltd | Professional & scientific | 2008 |
| Jarrod Bridges Limited | Administrative & support | 2002 |
| Jasmine House Consultancy Limited | Professional & scientific | 2007 |
| Jason Ramasami Limited | Arts & recreation | 2000 |
| Jawid Travels Ltd | Transport & logistics | 2022 |
| Jaykays Dance Company Limited | Arts & recreation | 2023 |
| Jaysdevelopmentconsultancy Ltd | Professional & scientific | 2022 |
| Jayyes Construction Ltd | Construction | 2017 |
| Jc.Organics Ltd | Hospitality | 2018 |
| Jcco 387 Limited | Financial services | 2015 |
| JCP Trading Ltd | Wholesale & retail | 2004 |
| JD Hospitality Ltd | Hospitality | 2023 |
| JDA Group Ltd | Information & communication | 2025 |
| JDW Couriers Ltd | Transport & logistics | 2025 |
| Jeff Heskine Limited | Professional & scientific | 2013 |
| Jelli Tots Nursery Limited | Health & social care | 2005 |
| Jellybean Technologies Ltd | Information & communication | 2019 |
| Jennings Estate Agents Ltd | Real estate | 2019 |
| JEO Finance Ltd | Professional & scientific | 2025 |
| JF Parks Limited | Hospitality | 2020 |
| JF Performing Arts Royston Limited | Arts & recreation | 2026 |
| JF Performing Arts Welwyn-Hatfield Limited | Arts & recreation | 2026 |
| Jg's Recycling Service Ltd | Wholesale & retail | 2022 |
| JGG International Transport Ltd | Transport & logistics | 2018 |
| JH Skin Clinic Ltd | Health & social care | 2019 |
| Jhalley Limited | Wholesale & retail | 2003 |
| JIG and a Swig Limited | Arts & recreation | 2024 |
| Jigsaw Accountants Limited | Professional & scientific | 2010 |
| JIM Mann Consulting Ltd | Information & communication | 2012 |
| Jimms (UK) Ltd | Administrative & support | 2013 |
| JIN Group Ltd | Wholesale & retail | 2023 |
| Jingyue Property Limited | Real estate | 2024 |
| Jingyue’S Paradise Limited | Hospitality | 2019 |
| JK and BJ Birkett and SON Limited | Agriculture & fishing | 2015 |
| JK Ballet Limited | Arts & recreation | 2026 |
| JKB Consultancy Services Limited | Professional & scientific | 2020 |
| Jkpropertyportfoliogroup Ltd | Real estate | 2025 |
| JLW Vehicle Sales Ltd | Wholesale & retail | 2024 |
| JM School of Dance Limited | Arts & recreation | 2023 |