| Inclusion Revolution Ltd | Education | 2022 |
| Incream Ltd | Manufacturing | 2026 |
| Incredible Roofing Ltd | Construction | 2025 |
| Indalohr Limited | Administrative & support | 2016 |
| Independent Car Sales & Servicing Limited | Wholesale & retail | 2005 |
| Independent Installations UK Limited | Construction | 2006 |
| Independent Practice Management Ltd | Administrative & support | 2012 |
| Indes Aviation Limited | Manufacturing | 2007 |
| Indian Grape Charmer Ltd | Wholesale & retail | 2021 |
| Indian Kitchen Foods Ltd | Hospitality | 2025 |
| Industrial Acoustics Company Limited | Manufacturing | 2016 |
| Industrial Cleaning Contractors Ltd | Administrative & support | 2023 |
| Industrial Door Repairs Ltd | Extraterritorial | 2023 |
| Industrial Sewn Products (Hampshire) Ltd | Construction | 2014 |
| Inert Landfill & Restoration Management Limited | Water & waste | 2020 |
| Inert Recycling (Sussex) Limited | Water & waste | 2024 |
| Inert Recycling (UK) Limited | Water & waste | 1999 |
| Inert Surveying & Design Limited | Professional & scientific | 2021 |
| Inert Tyre Support Limited | Wholesale & retail | 2020 |
| Infineo Solutions Ltd | Information & communication | 2013 |
| Infinity Kave Ltd | Wholesale & retail | 2024 |
| Influx Measurements Limited | Manufacturing | 1998 |
| Inform Scaffolding Services Ltd | Construction | 2013 |
| Informatic IT Systems Limited | Information & communication | 2011 |
| Information Services Consulting Limited | Information & communication | 2014 |
| Infused Consulting Limited | Professional & scientific | 2016 |
| Infused Solutions Limited | Administrative & support | 2021 |
| Inked Film Limited | Information & communication | 2025 |
| Inktronics Limited | Professional & scientific | 2013 |
| Innovation Markets Ltd | Professional & scientific | 2020 |
| Innovative Hygiene Supplies Ltd | Administrative & support | 2019 |
| Innspiration Pubs and Bars Ltd | Hospitality | 2023 |
| Inox Distribution Ltd | Wholesale & retail | 2023 |
| Inset OUT Limited | Information & communication | 2025 |
| Insight Home Improvements Ltd | Construction | 2025 |
| INSIGHT966 Ltd | Professional & scientific | 2019 |
| Insightful Designs Limited | Professional & scientific | 2023 |
| Insomniac Design Limited | Information & communication | 2014 |
| Inspiration AI Ltd | Information & communication | 2023 |
| Inspire Analytics Ltd | Information & communication | 2019 |
| Inspired Building Solutions Limited | Professional & scientific | 2012 |
| Inspired Construction Southern Limited | Construction | 2012 |
| Inspired Interiors & Property Maintenance Ltd | Construction | 2013 |
| Inspired Minds Learning Ltd | Education | 2026 |
| Insulate Hampshire Limited | Real estate | 2012 |
| Intamet Limited | Wholesale & retail | 1998 |
| INTEGR8 Sports Coaching Limited | Arts & recreation | 2017 |
| Integral Building Supplies Limited | Wholesale & retail | 2020 |
| Integral Cleaners Limited | Administrative & support | 2025 |
| Integral Resourcing Limited | Administrative & support | 2017 |
| Integral Services Limited | Wholesale & retail | 1988 |
| Integral Technology Systems Limited | Information & communication | 2016 |
| Integrated Backplane Solutions Limited | Manufacturing | 2001 |
| Integrated Case Management Ltd | Health & social care | 2019 |
| Integrated Technology & Control Limited | Manufacturing | 2011 |
| Integrity Network Consultants Ltd | Construction | 2023 |
| Intellivision Services Limited | Information & communication | 2024 |
| Inter County Office Supplies Limited | Information & communication | 1997 |
| Intercole Sub-Contract Services Limited | Manufacturing | 1994 |
| Intercole Systems Limited | Manufacturing | 1966 |
| Interior Building Products Limited | Wholesale & retail | 2004 |
| International Broadcast Communications Limited | Information & communication | 1996 |
| Interplay Development Limited | Professional & scientific | 1996 |
| Intetrost Global Services Limited | Construction | 2025 |
| Inversium Labs Ltd | Information & communication | 2025 |
| Invest Sea Ltd | Financial services | 2024 |
| Invictus 2000 Ltd | Information & communication | 2018 |
| Invincible Drain Care Holdings Limited | Financial services | 2025 |
| Invincible Drain Care Limited | Administrative & support | 2003 |
| Invincible Services Limited | Financial services | 2009 |
| Invol Education Ltd | Education | 2025 |
| Ionoptika Limited | Manufacturing | 1993 |
| Ipitome Ltd | Information & communication | 2024 |
| Iqur Diagnostics Limited | Professional & scientific | 2025 |
| Irao Ltd | Wholesale & retail | 2025 |
| IRH Electrical Services Ltd | Construction | 2011 |
| Iridium German Car Specialists Limited | Wholesale & retail | 2019 |
| Irix Technology Limited | Information & communication | 2022 |
| Iron Gate Tech Ltd | Information & communication | 2025 |
| Ironfire Furniture Limited | Professional & scientific | 2017 |
| Ironsight Games Ltd | Hospitality | 2019 |
| Iruk (Waste Planning & Consultancy) Limited | Professional & scientific | 2019 |
| Isalie Properties Ltd | Real estate | 2024 |
| ISH Clothing Ltd | Wholesale & retail | 2025 |
| Isla Clyde Limited | Real estate | 2019 |
| Island Building Contractors Ltd | Construction | 2018 |
| Island View Sennen Cove Limited | Real estate | 2012 |
| Isouk Limited | Information & communication | 2017 |
| Istanbul Grill Since 1988 Ltd | Hospitality | 2026 |
| Istanbul H S Ltd | Other services | 2022 |
| ISU Consult Limited | Information & communication | 2024 |
| IT & Business Consulting Limited | Information & communication | 2011 |
| IT Hardware Direct Limited | Information & communication | 2007 |
| IT Outcomes Ltd | Information & communication | 2017 |
| IT2 UK Services Limited | Information & communication | 2023 |
| Itchen Valley Holdings Ltd | Financial services | 2021 |
| Itchen Valley Joiners Limited | Manufacturing | 2002 |
| Itchen Valley Structures Limited | Construction | 2012 |
| Itooth Holding Limited | Financial services | 2022 |
| Itooth Limited | Health & social care | 2009 |