| Hoip Consulting Ltd | Information & communication | 2010 |
| Hoip Telecom Limited | Information & communication | 2009 |
| Hoja Ltd | Manufacturing | 2026 |
| Hold Fast Projects Ltd | Professional & scientific | 2015 |
| Hole Farm Limited | Other services | 2024 |
| Holistic Communications Limited | Information & communication | 2020 |
| Holistic Hideaway Limited | Health & social care | 2015 |
| Hollow Space Creations Ltd | Wholesale & retail | 2021 |
| Holly Services Limited | Professional & scientific | 2022 |
| Holt & Haskell Limited | Transport & logistics | 1946 |
| Holt Court Residents (Romsey) Limited | Real estate | 2012 |
| Holz Design Ltd | Construction | 2015 |
| Holz Development Ltd | Wholesale & retail | 2023 |
| Home Grown Brixton Ltd | Hospitality | 2020 |
| Home Solution Services Limited | Real estate | 2019 |
| Horse Health Wessex Holdings Limited | Administrative & support | 2021 |
| Horsefair (Romsey) Management Limited | Real estate | 2005 |
| Horsefair House Limited | Real estate | 2015 |
| Hound Accounting Ltd | Professional & scientific | 2024 |
| Hound Wood Management Limited | Agriculture & fishing | 1995 |
| House 2 Home (Hampshire) Developements Ltd | Construction | 2017 |
| House of Arvind Limited | Real estate | 2018 |
| Hovell Hall Limited | Wholesale & retail | 2018 |
| HOW to Make Limited | Information & communication | 2017 |
| HOY Surf Ltd | Wholesale & retail | 2020 |
| HR Inc Limited | Administrative & support | 2009 |
| HRG Endeavours Ltd | Administrative & support | 2021 |
| HRG Machinery Hire Ltd | Administrative & support | 2021 |
| HRG Tree Surgeons Partners LLP | | 2019 |
| Hueman Consult Ltd | Information & communication | 2025 |
| Hughes Forty Winks Limited | Health & social care | 2013 |
| Humber Resources Group Limited | Water & waste | 2024 |
| Hunter Fire Safety Limited | Public administration | 2022 |
| Hushed UP Ltd | Information & communication | 2023 |
| Huskins Marketing Ltd | Information & communication | 2018 |
| HW Therapy Services Ltd | Health & social care | 2025 |
| Hythe Group Limited | Financial services | 2013 |
| Hythe Properties Limited | Construction | 2019 |
| Hythe Tender Services Limited | Professional & scientific | 2021 |
| I Boat Valet Ltd | Manufacturing | 2018 |
| I Heat Solutions Ltd | Construction | 2013 |
| I M C a D (UK) Limited | Professional & scientific | 2019 |
| I S Consulting Limited | Information & communication | 1992 |
| I-Windo Ltd | Construction | 2010 |
| IAN Hounsome Design Limited | Information & communication | 2012 |
| ILG Medical Limited | Health & social care | 2019 |
| Ilika PLC | Professional & scientific | 2010 |
| Ilika Technologies Ltd | Professional & scientific | 2004 |
| IMB Orthopaedics Limited | Health & social care | 2020 |
| Imeson & Finch Limited | Professional & scientific | 1928 |
| Immo Grain Limited | Wholesale & retail | 2003 |
| Impact 2 Limited | Professional & scientific | 2003 |
| Impact Call Centre Limited | Administrative & support | 2013 |
| Impact Early Years Ltd | Information & communication | 2024 |
| Impact Films Media Limited | Information & communication | 2023 |
| Impaq Ltd | Information & communication | 2024 |
| Impct Ltd | Information & communication | 2024 |
| Impetus Pharma Ltd | Professional & scientific | 2017 |
| IN the Vortex Limited | Information & communication | 2015 |
| IN4STRUCTURE Limited | Construction | 2018 |
| Independent Carpentry Ltd | Construction | 2017 |
| Index Communications Meeting Services Limited | Administrative & support | 2009 |
| Indomita Limited | Manufacturing | 2023 |
| Ineo Life Ltd | Education | 2012 |
| Inidam Limited | Professional & scientific | 2007 |
| Inlieu Services Limited | Professional & scientific | 2014 |
| Innate Values Ltd | Professional & scientific | 2023 |
| Inncomparison Ltd | Hospitality | 2013 |
| Innovate Electrical Supplies Limited | Wholesale & retail | 2009 |
| Innovent Consultants Events and Education Limited | Education | 2024 |
| Innovent Consultants Limited | Health & social care | 2010 |
| Innovent Healthcare LLP | | 2025 |
| Innovesus Limited | Wholesale & retail | 2020 |
| Innprofit Ltd | Hospitality | 2012 |
| Inspire to Learn Consultancy Limited | Professional & scientific | 2010 |
| Inspired Green Dragon Ltd | Construction | 2013 |
| INTEGR8 IT Limited | Information & communication | 2021 |
| Intelecare Ltd | Information & communication | 2025 |
| Intelligent Solutions in Transport Limited | Professional & scientific | 2009 |
| Intentio Holdings Limited | Financial services | 2025 |
| Interior Decorating Specialists Ltd | Administrative & support | 2017 |
| Interventional Oncologist LLP | | 2022 |
| Invasive Species Ltd | Other services | 2019 |
| Invasive Weeds Ltd | Other services | 2019 |
| Invisible Hand Ltd | Information & communication | 2007 |
| Iosc Ltd | Wholesale & retail | 2003 |
| Iphoum (Management) Ltd | Education | 2008 |
| Irene Paterson Solutions Ltd | Administrative & support | 2008 |
| Iron Bears Limited | Real estate | 2020 |
| Iron Yolk Ltd | Wholesale & retail | 2026 |
| Irongate Marketing Ltd | Professional & scientific | 2020 |
| Isffc Ltd | Other services | 2021 |
| Islim Radiology Ltd | Health & social care | 2022 |
| Isol Properties Limited | Real estate | 2017 |
| ISR Engineering Ltd | Professional & scientific | 2022 |
| Ists Wholesale Ltd | Wholesale & retail | 2019 |
| Isunn Tanning Limited | Other services | 2012 |
| Italian Culinary Services Ltd | Wholesale & retail | 2016 |
| Itchen 2 Train Ltd | Arts & recreation | 2022 |
| Itchen Garage Limited | Other services | 2003 |