| Island Harbour Hammerhead Company Limited | Households | 2009 |
| Island Photo Centre (IW) Limited | Wholesale & retail | 2001 |
| Island Ribs Limited | Manufacturing | 2014 |
| Island Styles Designs Ltd | Wholesale & retail | 2023 |
| Isle Forty One Advisors Limited | Professional & scientific | 2018 |
| Isle Forty One Legal Advisors Limited | Professional & scientific | 2020 |
| Isle of Wight Specsavers Hearcare Limited | Wholesale & retail | 2012 |
| Islington Specsavers Limited | Wholesale & retail | 2007 |
| Islington Visionplus Limited | Wholesale & retail | 2007 |
| Isobelles Care Limited | Health & social care | 2019 |
| Isotools Limited | Wholesale & retail | 1999 |
| Isprayit East Ltd | Construction | 2025 |
| Isprayit West Ltd | Construction | 2025 |
| IT Pump Services Limited | Manufacturing | 2025 |
| Italiwalls Ltd | Construction | 2020 |
| Itchen Electrical Services Limited | Construction | 2003 |
| ITD Consultants Limited | Professional & scientific | 2011 |
| Itel Systems UK Ltd | Information & communication | 2018 |
| Itelligentsia Global Limited | Information & communication | 2010 |
| Item Software Limited | Information & communication | 2011 |
| Itgl Limited | Information & communication | 2025 |
| Itlocker Limited | Information & communication | 2021 |
| Itsm Support Limited | Information & communication | 2018 |
| Ittess Ltd | Real estate | 2023 |
| IVF Laboratory Solutions Ltd | Health & social care | 2017 |
| Ivida Ltd | Professional & scientific | 2022 |
| Ivory and INK Fine Art Ltd | Wholesale & retail | 2026 |
| Ivory Catering & Events Management (Icem) Limited | Hospitality | 2017 |
| Iwantabox Ltd | Wholesale & retail | 2014 |
| IWS (Holdings) Limited | Professional & scientific | 2008 |
| IWS Trustees Limited | Professional & scientific | 2023 |
| IYI Logistics Ltd | Transport & logistics | 2018 |
| J & a Finishing Services Limited | Manufacturing | 2007 |
| J & B Education Limited | Education | 2023 |
| J & B Hopkins Limited | Construction | 1978 |
| J & G Environmental Limited | Water & waste | 1998 |
| J & M Nutrition International Ltd | Wholesale & retail | 2023 |
| J & N Aluminium Systems Ltd | Manufacturing | 2015 |
| J a Rees Limited | Construction | 2018 |
| J C Carr Limited | Construction | 2010 |
| J Campbell Joinery Limited | Construction | 2026 |
| J Chopra Screeding Limited | Construction | 2016 |
| J Clohessy Ltd | Information & communication | 2017 |
| J D S Jointing Ltd | Construction | 2015 |
| J E Building Contractors Ltd | Construction | 2016 |
| J F Heating & Plumbing Solutions Limited | Construction | 2023 |
| J Henderson Roofing Services Limited | Construction | 2014 |
| J Humphry Consulting Ltd | Professional & scientific | 2012 |
| J Iacobucci Ltd | Construction | 2023 |
| J M Harzz Ltd | Wholesale & retail | 2023 |
| J N Tree Care Ltd | Administrative & support | 2019 |
| J Saunders Transport Ltd | Transport & logistics | 2025 |
| J Squared Carpentry Ltd | Manufacturing | 2023 |
| J W European Limited | Wholesale & retail | 1994 |
| J W Mobility Services Ltd | Manufacturing | 2018 |
| J Wagner Ltd | Construction | 2013 |
| J Waugh Consultancy Ltd | Information & communication | 2005 |
| J White Electrical Solutions Ltd | Professional & scientific | 2025 |
| J Wraithmell Ltd | Financial services | 2024 |
| J&B Targett Brickwork Ltd | Construction | 2021 |
| J&H Humphrey Ltd | Professional & scientific | 2024 |
| J&O IT Solutions Limited | Information & communication | 2010 |
| J'S Janitors Ltd | Administrative & support | 2021 |
| J. Anderson Holdings Limited | Financial services | 2025 |
| J. Clubb & SON Limited | Mining & quarrying | 1956 |
| J. Humphry Associates Limited | Professional & scientific | 1979 |
| J. Robbins and SON Limited | Construction | 2004 |
| J.B Groundworks Southern Ltd | Construction | 2023 |
| J.Stan. Engineering Ltd | Manufacturing | 2012 |
| J.Storey Construction Ltd | Construction | 2024 |
| J10 Consultancy Limited | Information & communication | 2025 |
| J2S Consulting Limited | Information & communication | 2011 |
| JA Management Services Ltd | Professional & scientific | 2007 |
| Jaape Ltd | Construction | 2011 |
| Jack Dear Solutions Ltd | Professional & scientific | 2026 |
| Jack Hutchinson - Medium Ltd | Other services | 2025 |
| Jack Priestley Cafes Ltd | Hospitality | 2024 |
| Jackson & Collings Holdings Limited | Financial services | 2022 |
| Jacobs Foreman Developments Ltd | Construction | 2002 |
| Jacobs House Ltd | Real estate | 2015 |
| Jacobsbits Ltd | Wholesale & retail | 2025 |
| Jade Mendes Hairline Ltd | Arts & recreation | 2023 |
| Jade Network Services Ltd | Information & communication | 2019 |
| Jade Swimming T/A Swimtime South Coast LLP | | 2024 |
| Jade Telecom Ltd | Wholesale & retail | 2018 |
| Jaffer UK Investments Ltd | Financial services | 2024 |
| Jaguar Engineering Group Limited | Construction | 2010 |
| Jaguar Enterprises Ltd | Households | 2025 |
| Jakes Flakes South Ltd | Hospitality | 2026 |
| Jakk Properties Hampshire Ltd | Real estate | 2019 |
| James Beckwith Electrical Limited | Construction | 2004 |
| James Carlisle Associates Limited | Professional & scientific | 2024 |
| James Hunt Installations Limited | Administrative & support | 2024 |
| James Morton-Haworth Limited | Administrative & support | 2012 |
| James Warren Recycling Ltd | Water & waste | 2019 |
| Jamie Leggett Builders Ltd | Construction | 2019 |
| Jamiesons Services Ltd | Manufacturing | 2020 |
| JAN Nanak Limited | Real estate | 2018 |
| Janascaul Investments Limited | Real estate | 1988 |
| Jancon Ltd | Information & communication | 2024 |