| Intuitive AI Ltd | Professional & scientific | 2020 |
| Intuitive Leadership Limited | Administrative & support | 2010 |
| Intuitive Thinking Limited | Information & communication | 2016 |
| Invictus Finance Limited | Financial services | 2014 |
| Invictus Investments Limited | Financial services | 2014 |
| Invictus Trustees Limited | Financial services | 2014 |
| Ionfibre Limited | Information & communication | 2022 |
| Ioptosystems Limited | Professional & scientific | 2015 |
| IR Sussex Ltd | Financial services | 2016 |
| Irbid Ltd | Hospitality | 2025 |
| Iris Bistro Ltd | Hospitality | 2024 |
| Iriy Limited | Professional & scientific | 2007 |
| Ironwood International Ltd | Wholesale & retail | 2026 |
| Ironwood Property Investments Limited | Real estate | 2026 |
| Ironwood Property Limited | Real estate | 2021 |
| Irradiate Ltd | Arts & recreation | 2024 |
| Iruma Limited | Hospitality | 2024 |
| ISA Media Ltd | Extraterritorial | 2004 |
| Isaac Incisors Limited | Health & social care | 2026 |
| Isaayajewellery UK Ltd | Wholesale & retail | 2026 |
| ISE Brighton Ltd | Education | 2023 |
| ISE Language Limited | Education | 2006 |
| Iseek Limited | Wholesale & retail | 2010 |
| ISF8118 Ltd | Administrative & support | 2020 |
| Isle of Wight Grange Limited | Energy | 2013 |
| Ismas Limited | Wholesale & retail | 2001 |
| Isotropic Technology Limited | Information & communication | 2018 |
| Istefanous Limited | Real estate | 2022 |
| IT Document Solutions Ltd | Information & communication | 2014 |
| It's a Disgrace Ltd | Real estate | 2009 |
| Italia 24 Limited | Hospitality | 2015 |
| Italian Cottage Limited | Hospitality | 2021 |
| Italianrestaurantbtn Ltd | Hospitality | 2024 |
| Itbn Ltd | Arts & recreation | 2022 |
| Itds Mailroom Solutions Limited | Information & communication | 2017 |
| Itds Managed Services Limited | Information & communication | 2020 |
| Itec UK International Students Limited | Education | 2022 |
| ITP Management Ltd | Professional & scientific | 2002 |
| ITS OUR Planet TOO Limited | Wholesale & retail | 2020 |
| Itsm R US Ltd | Information & communication | 2017 |
| IV Marketing AI Limited | Information & communication | 2024 |
| IVA Troj Ltd | Professional & scientific | 2022 |
| Ivor Place Investments Limited | Administrative & support | 1958 |
| IVY Corporate Finance Limited | Professional & scientific | 2010 |
| IVY Union Limited | Hospitality | 2011 |
| Iyris Technology Ltd | Professional & scientific | 2018 |
| Izzy Burton Ltd | Arts & recreation | 2020 |
| J & a Consultancy 2021 Limited | Professional & scientific | 2020 |
| J & a Lloyd Commercial Limited | Real estate | 2021 |
| J & a Lloyd Property Services Limited | Real estate | 2016 |
| J & B Reinforcement Specialists Ltd | Real estate | 2003 |
| J & S Structured Solutions Limited | Professional & scientific | 2016 |
| J a Consultancy Services Ltd | Administrative & support | 2021 |
| J a Productivity Limited | Hospitality | 2025 |
| J B Wood Accountancy Services Limited | Professional & scientific | 2003 |
| J Cook Properties Ltd | Real estate | 2021 |
| J Davies Building Limited | Construction | 1996 |
| J Holder-Spriggs Services Limited | Administrative & support | 2015 |
| J J J T Holdings Ltd | Real estate | 2025 |
| J J Roberts Plastering & Building Services Limited | Construction | 2003 |
| J J Services (Brighton) Ltd | Construction | 2009 |
| J M Construction Systems Limited | Construction | 2008 |
| J R S Industrial Services Limited | Professional & scientific | 1998 |
| J S Developments (Southern) Limited | Construction | 2013 |
| J T Services (South East) Limited | Information & communication | 2013 |
| J Turnbull Limited | Construction | 2005 |
| J W Mechanical Ltd | Construction | 2019 |
| J&G Dental Limited | Health & social care | 2025 |
| J&J Fine Dining Limited | Hospitality | 2016 |
| J&N Smart Property Solutions Ltd | Real estate | 2026 |
| J. Barker (London) Limited | Transport & logistics | 1951 |
| J.A. Cobbett P & H Limited | Construction | 2003 |
| J.F. Robey & Co. Limited | Real estate | 1950 |
| J.G.P.C Consulting Ltd. | Information & communication | 2015 |
| J.T.Pugh Construction & Renovation Ltd | Construction | 2016 |
| J.W.C Liquid & GAS Services Limited | Construction | 2015 |
| J.W.C Mechanical Services Limited | Construction | 2019 |
| JA Orchard Limited | Real estate | 2024 |
| Jack Hanrahan Fitness Limited | Health & social care | 2017 |
| Jackson Auto Ltd | Wholesale & retail | 2018 |
| Jackson Plumbing & Heating (Contractors) Limited | Construction | 1997 |
| Jackson Waste Group Ltd | Water & waste | 2022 |
| Jacobi Properties Ltd | Real estate | 2019 |
| Jacopan LLP | | 2016 |
| Jacqueline Fowler Limited | Information & communication | 2014 |
| Jacs Property LLP | | 2021 |
| Jade Kitchen House Limited | Hospitality | 2025 |
| Jade Leisure Limited | Real estate | 2012 |
| Jade Leisure Properties Limited | Real estate | 2024 |
| Jade Stanley Limited | Financial services | 1998 |
| Jades Three Angels Limited | Wholesale & retail | 2015 |
| JAF Inns Ltd | Hospitality | 2011 |
| JAH Company Services Limited | Administrative & support | 2015 |
| Jahed Iqbal Limited | Hospitality | 2013 |
| Jain Orthodontics Ltd | Health & social care | 2022 |
| Jalna Contract Hire Limited | Transport & logistics | 2003 |
| James Albert Burton Limited | Financial services | 2020 |
| James Burbidge Design Ltd | Professional & scientific | 2017 |
| James Chase Group Limited | Financial services | 2019 |
| James Christie-Miller Limited | Information & communication | 2016 |