| IP Dwellings Ltd | Real estate | 2022 |
| IP Plastering Ltd | Construction | 2023 |
| IP Services Hampshire Ltd | Administrative & support | 2024 |
| Iqbal SUB Limited | Wholesale & retail | 2026 |
| IQH Consulting Limited | Other services | 2011 |
| Irasyaimase Ltd | Professional & scientific | 2023 |
| Irbk Limited | Construction | 2024 |
| Irgb Technical Services Limited | Health & social care | 2013 |
| Ironshield Secure Services Limited | Wholesale & retail | 2024 |
| Iroofing Ltd | Construction | 2019 |
| Irving & Co. Brewers Limited | Manufacturing | 2007 |
| Isbilling Ltd | Information & communication | 2015 |
| Isfs Consultancy Limited | Professional & scientific | 2024 |
| Isherwood & Hutchinson Limited | | 1968 |
| Island City Cafe Ltd | Hospitality | 2026 |
| Island Laboratories IW Limited | Health & social care | 2026 |
| Island Linen Ltd | Other services | 2026 |
| Island Wide Refuse Limited | Water & waste | 2026 |
| Isobel Jackson Ltd | Manufacturing | 2020 |
| Istan Grill Ltd | Hospitality | 2022 |
| IT Drive Limited | Transport & logistics | 2023 |
| IT EL Duende Ltd | Professional & scientific | 2015 |
| IT Group Portsmouth Ltd | Construction | 2019 |
| IT Support Consultancy Ltd | Information & communication | 2019 |
| Ital Group Limited | Information & communication | 2003 |
| Italia&Sapori Ltd | Hospitality | 2025 |
| Italk Group Limited | Professional & scientific | 2026 |
| Itchen Domain Management Ltd | Administrative & support | 2013 |
| Itchen Grange Management Company Limited | Households | 1989 |
| Itechfirst Limited | Other services | 2018 |
| Itechfirst Plus Ltd | Other services | 2023 |
| IU Design Ltd | Professional & scientific | 2025 |
| Iungureanu Ltd | Transport & logistics | 2025 |
| Ivo-S Enterprise Ltd | Transport & logistics | 2016 |
| IVY Healthcare Recruitment Ltd | Health & social care | 2023 |
| IVY Homecare Limited | Public administration | 2020 |
| IVY Mill Lane Properties Limited | Construction | 2025 |
| Ixl.It.Com Ltd | Extraterritorial | 2014 |
| Izah Investments Limited | Real estate | 2019 |
| Izzy Trans Ltd | Transport & logistics | 2019 |
| J & a Fascia, Soffit & Guttering Limited | Construction | 2025 |
| J & C Mega Extreme Rides Limited | Arts & recreation | 2012 |
| J & N HR and H&S Advisors LLP | | 2022 |
| J & P Dairy Ltd | Wholesale & retail | 2013 |
| J & S Band Limited | Professional & scientific | 2010 |
| J & V Pharma Limited | Wholesale & retail | 2020 |
| J 2 S Training Limited | Health & social care | 2011 |
| J a Build and Develop Ltd | Construction | 2026 |
| J and L Waste Solutions Ltd | Water & waste | 2025 |
| J B Travel Limited | Administrative & support | 2014 |
| J C L (U.K.) Developments Limited | Real estate | 2018 |
| J C L (U.K.) Investments Limited | Real estate | 2018 |
| J C L (U.K.) Ltd | Wholesale & retail | 1996 |
| J C L (UK) Holdings Limited | Real estate | 2014 |
| J C L Cobham and N S Limited | Wholesale & retail | 2019 |
| J C L Properties Limited | Real estate | 2014 |
| J Create Ltd. | Wholesale & retail | 2022 |
| J Crowe Contracting Ltd | Construction | 2026 |
| J D S Installations Limited | Construction | 2003 |
| J D Window Solutions Ltd | Construction | 2022 |
| J Dagostino (Portsmouth) Limited | Wholesale & retail | 1946 |
| J Glazing Ltd | Construction | 2020 |
| J H Ventilation Services Ltd | Construction | 2011 |
| J Howard Roofing Ltd | Construction | 2012 |
| J K B Home Improvements Limited | Construction | 2025 |
| J K Woodworks Limited | Manufacturing | 2007 |
| J L Curtis Limited | Construction | 2025 |
| J L Glass Limited | Professional & scientific | 2005 |
| J Logan Electrical Ltd | Construction | 2018 |
| J Luck Consulting Ltd | Information & communication | 2023 |
| J M Automatics Limited | Manufacturing | 1995 |
| J M Bespoke Carpentry Ltd | Construction | 2025 |
| J M Property Management (Southsea) Limited | Health & social care | 2005 |
| J Martin Construction and Building Limited | Construction | 2025 |
| J Mayo Engineering Ltd | Administrative & support | 2020 |
| J Morgan Holdings Limited | Financial services | 2024 |
| J N G Properties LLP | | 2018 |
| J Newell Holdings Ltd | Financial services | 2026 |
| J P Capes Ltd | Construction | 2014 |
| J P S Holdings Limited | Wholesale & retail | 2015 |
| J P West Plumbing & Heating Ltd | Construction | 2019 |
| J R Construction Management Ltd | Construction | 2014 |
| J R Irvin Catering Ltd | Hospitality | 2021 |
| J S H Couriers Ltd | Transport & logistics | 2025 |
| J&A Investment Group Ltd | Real estate | 2025 |
| J&B Cash and Carry Ltd | Hospitality | 2024 |
| J&E Woodward Property Managment Ltd | Real estate | 2025 |
| J&F Car Sales Ltd | Wholesale & retail | 2026 |
| J&K Enterprises Ltd | Health & social care | 2013 |
| J&L Industrial Supplies Ltd | Other services | 2026 |
| J&P Property Services Ltd | Real estate | 2025 |
| J&R Roofing Ltd | Construction | 2019 |
| J&T Contracting Ltd | Construction | 2025 |
| J&V Home Care and Support Limited | Health & social care | 2025 |
| J. Ashwell Services Limited | Professional & scientific | 1984 |
| J. Edwards & SON (Funeral Directors) Limited | Professional & scientific | 1976 |
| J. Warton Carpentry Limited | Manufacturing | 2020 |
| J.A.Smith(Waterlooville)Limited | Construction | 1960 |
| J.Butcher & Sons Limited | Real estate | 1961 |
| J.E.M Ecommerce Limited | Wholesale & retail | 2025 |