| I-Onasia (UK) Limited | Professional & scientific | 2022 |
| I.G. Developments (Southern) Limited | Construction | 2007 |
| IAN R Glew Limited | Construction | 2003 |
| IAN Upstone Graphic Design Ltd | Administrative & support | 2012 |
| ICA Property Ltd | Real estate | 2023 |
| Icare 7/24 Limited | Health & social care | 2019 |
| Icelink Group Ltd | Transport & logistics | 2020 |
| Icelink Transport Ltd | Transport & logistics | 2011 |
| Iceman Holdings Ltd | Information & communication | 2021 |
| IDB Construction Ltd | Construction | 2024 |
| Ideas Alliance CIC | Information & communication | 2016 |
| IDT Southern Limited | Transport & logistics | 2016 |
| IES Electrical Ltd | Construction | 2007 |
| Ignite Service Limited | Construction | 2012 |
| Igt-Pa Ltd | Information & communication | 2024 |
| Ikhlaq&Co Ltd | Wholesale & retail | 2022 |
| Iksana Vipani Ltd | Professional & scientific | 2023 |
| Ilex Content Strategies Limited | Professional & scientific | 2012 |
| IMG DO IT 4 U Ltd | Administrative & support | 2025 |
| Imi-Teak Limited | Manufacturing | 2010 |
| Immanuel Church, Chichester | Other services | 2010 |
| Impact Digital Marketing Services Ltd | Information & communication | 2021 |
| Impact Point Films Ltd | Arts & recreation | 2025 |
| Impactadvise Ltd | Professional & scientific | 2023 |
| Imperial (W.Sx) Ltd | Construction | 2019 |
| Imperico Ltd | Education | 2018 |
| Imperium Strength Fitness Centre Ltd. | Arts & recreation | 2025 |
| Imprint Ecology Limited | Professional & scientific | 2023 |
| IN Equilibrium Ltd | Professional & scientific | 2025 |
| IN Living Colour Ltd | Wholesale & retail | 2017 |
| IN the Country Ltd | Information & communication | 2017 |
| IN8 Living Limited | Health & social care | 2025 |
| Inavika Limited | Manufacturing | 2018 |
| Inbetween Days Photography Ltd | Professional & scientific | 2018 |
| Incodia Ltd | Other services | 2013 |
| Independent Examiners Ltd. | Professional & scientific | 1996 |
| Independent Fire and Safety Training Limited | Administrative & support | 2000 |
| Independent Search Partnership LLP | | 2010 |
| Independent Service Company Limited | Professional & scientific | 1996 |
| Indigo Leaf Ltd. | Information & communication | 2017 |
| Industrial Ceramic Catalysts Limited | Manufacturing | 2024 |
| Infigo Software Limited | Information & communication | 2010 |
| Infinity Lighting Solutions Ltd | Wholesale & retail | 2024 |
| Infinity Shopfitting Limited | Construction | 2013 |
| Initiis Property Services Limited | Real estate | 2024 |
| Inkpact Marketing Ltd | Other services | 2013 |
| Inksmiths Apparel Ltd | Wholesale & retail | 2024 |
| Innovate Electrics Ltd | Construction | 2018 |
| Innovation in Engineering Ltd | Professional & scientific | 2019 |
| Innovative Options Ltd | Professional & scientific | 2015 |
| Inside OUT Lifestyle Developments Limited | Construction | 2018 |
| Inside OUT Lifestyle Ltd | Construction | 2010 |
| Inside OUT Wellness Cafe Ltd | Hospitality | 2026 |
| Inside Outside Design Ltd | Information & communication | 2006 |
| Inside Performance Consulting Limited | Professional & scientific | 2009 |
| Insight (Rswc) Limited | Administrative & support | 2019 |
| Insightx Coaching Limited | Professional & scientific | 2026 |
| Inspired Business Coaching Limited | Professional & scientific | 2002 |
| Inspired Design Studio Limited | Information & communication | 2007 |
| Inspiring Media Ltd | Information & communication | 2011 |
| Instinct Landscapes Ltd | Construction | 2024 |
| Integrated Security Engineering Limited | Administrative & support | 2010 |
| Intelipack Limited | Administrative & support | 2018 |
| Intellectual Property Management Limited | Professional & scientific | 1997 |
| Intelligent Management Solutions Limited | Professional & scientific | 2019 |
| Inter Products Limited | Construction | 2000 |
| Intercare Orthopaedic Services Ltd | Health & social care | 2001 |
| Intercole Management Services Ltd | Professional & scientific | 2025 |
| Intercontinental UK Limited | Wholesale & retail | 2004 |
| Intergalactic Group Limited | Arts & recreation | 2012 |
| Interior Systems (Midlands) Ltd | Construction | 2009 |
| Interior Worx Ltd | Wholesale & retail | 2026 |
| International Animal Relief Limited | Professional & scientific | 2017 |
| International Christian Consulate | Other services | 2016 |
| International Education Network Limited | Education | 2024 |
| International Feng Shui Academy Limited | Education | 2025 |
| International Harbour Masters' Association | Other services | 2026 |
| International Superyacht Management Limited | Professional & scientific | 2018 |
| Internet Direct (Chichester) Limited | Information & communication | 2000 |
| Intersas Limited | Professional & scientific | 2016 |
| Inthemix Mixology Ltd | Other services | 2024 |
| Inventory Management Associates (UK) Limited | Information & communication | 1997 |
| Inverse Communications Limited | Professional & scientific | 2000 |
| Inwood House Management Co. Limited | Households | 2012 |
| Ioannides-Hoey Limited | Professional & scientific | 2024 |
| IP Quest Limited | Professional & scientific | 2013 |
| Iris Sales Ltd | Other services | 2019 |
| Iron Edge Machinery Ltd | Manufacturing | 2025 |
| Ironhorse Recruitment Ltd | Administrative & support | 2025 |
| IS IT Art Limited | Wholesale & retail | 1995 |
| Isaap Ltd | Wholesale & retail | 2023 |
| Isabel Neighbour Refined Homes Limited | Construction | 2020 |
| ISC A-List Airline Limited | Transport & logistics | 2008 |
| ISC Air Freight First Limited | Transport & logistics | 2008 |
| ISC Airline Group Limited | Professional & scientific | 2008 |
| ISC Best Practice Consultancy Limited | Manufacturing | 2005 |
| ISC Mini-Telecom Limited | Information & communication | 2007 |
| ISG Electrical Ltd | Construction | 2022 |
| Isis Integration Limited | Administrative & support | 1998 |
| ISO Concepts Limited | Professional & scientific | 2015 |