| Incendo Digital Ltd | Professional & scientific | 2011 |
| Incito Strategies Consulting Limited | Professional & scientific | 2006 |
| Inclined Publishing Limited | Information & communication | 2015 |
| Indah Ltd | Administrative & support | 2023 |
| Indeed (DBT) Limited | Other services | 2018 |
| Independent Cinema Portsmouth C.I.C. | Arts & recreation | 2012 |
| Independent Enterprise Solutions Ltd | Construction | 2023 |
| Independent Heat Transfer Services Limited | Professional & scientific | 2002 |
| Independent Insight Social Work Consultancy Limited | Health & social care | 2026 |
| Indiair Ltd | Administrative & support | 2010 |
| Indifilmproduction Ltd | Information & communication | 2025 |
| INDIK8A.COM Limited | Wholesale & retail | 2018 |
| Indoor Furniture Group Limited | Wholesale & retail | 2012 |
| Industrial Facades (Southern) Ltd | Construction | 2022 |
| Industrial Roofing, Cladding and Consultancy Ltd | Construction | 2011 |
| Inert Limited | Professional & scientific | 2016 |
| Ineza Group Ltd | Information & communication | 2022 |
| Infinite Envision Limited | Health & social care | 2019 |
| Infinite Events Ltd | Administrative & support | 2024 |
| Infinite Origins Ltd | Transport & logistics | 2021 |
| Infinity Automotive Solutions Limited | Wholesale & retail | 2019 |
| Infinity Drivers Ltd | Administrative & support | 2020 |
| Infinity International Stiches Limited | Manufacturing | 2024 |
| Infinity Leasing Solutions Limited | Administrative & support | 2025 |
| Infinity Property Services Limited | Construction | 2015 |
| Influence Barber Limited | Wholesale & retail | 2025 |
| Infonetmedia Limited | Information & communication | 2010 |
| Infrastructure Consultancy Group Ltd | Professional & scientific | 2022 |
| Ingenica EBT Trustee Limited | Administrative & support | 2019 |
| Ingenica Solutions Limited | Information & communication | 2012 |
| Ingenium Games Ltd | Information & communication | 2015 |
| INK Doctors (Southern) Ltd | Arts & recreation | 2023 |
| INK Ease Limited | Wholesale & retail | 2025 |
| INK N Pixels Ltd | Manufacturing | 2024 |
| Inner Mongolia 79 Ltd | Hospitality | 2022 |
| Innit Delivery Ltd | Transport & logistics | 2026 |
| Innovanti Group Limited | Information & communication | 2016 |
| Innovanti Limited | Information & communication | 2016 |
| Innovative Living Limited | Real estate | 2014 |
| Innovative Procurement Ltd | Professional & scientific | 2012 |
| Inovo Property Group Limited | Real estate | 2022 |
| Insanetrain Ltd | Information & communication | 2024 |
| Inscope 360 Limited | Information & communication | 2026 |
| Inscope Digital Limited | Information & communication | 2026 |
| Inside AUT Ltd | Education | 2022 |
| Inside.Out Surrey Ltd | Construction | 2017 |
| Insignis Consultancy Limited | Information & communication | 2020 |
| Insignis Talent Limited | Extraterritorial | 2013 |
| Insignlanguage Limited | Health & social care | 2017 |
| Inspector Electrical Ltd | Construction | 2025 |
| Inspire Car Sales Limited | Wholesale & retail | 2014 |
| Inspire ME Fit Limited | Arts & recreation | 2016 |
| INSPIRE44 Limited | Information & communication | 2024 |
| Inspired 2 Dance Ltd | Arts & recreation | 2009 |
| Inspirity Auto Ltd | Wholesale & retail | 2025 |
| Install (Mechanical Services) Limited | | 1979 |
| Instanit Ltd | Information & communication | 2025 |
| Instinct Delivery and Taxi Ltd | Transport & logistics | 2025 |
| Instrumental Living Academy Ltd | Education | 2023 |
| Insync Networks Ltd | Construction | 2012 |
| Integrated Interiors Limited | Construction | 2015 |
| Integrated Marine Services GRP Limited | Professional & scientific | 2015 |
| Integrated Marine Services Limited | Transport & logistics | 2000 |
| Integratedx UK Ltd | Hospitality | 2025 |
| Integrity Furniture Solutions Limited | Wholesale & retail | 2021 |
| Intelegal Ltd | Professional & scientific | 2016 |
| Intellectual Properties Limited | Construction | 1999 |
| Intellispear Limited | Professional & scientific | 2018 |
| Intend Technologies Limited | Information & communication | 2001 |
| Inter City Football Club Ltd | Arts & recreation | 2025 |
| Inter City Sports and Social Club Ltd | Hospitality | 2025 |
| Inter Consult Europe Ltd | Extraterritorial | 2017 |
| Interactive Machines LAB Ltd | Professional & scientific | 2018 |
| Intercash Limited | Real estate | 1994 |
| Interion Limited | Wholesale & retail | 2012 |
| Interlinx Consulting Limited | Administrative & support | 2025 |
| Internal Surveys Limited | Mining & quarrying | 2007 |
| International Associates CTS Ltd | Extraterritorial | 2016 |
| International Hair Cosmetics Holdings Limited | Professional & scientific | 2020 |
| International Hair Cosmetics Limited | Wholesale & retail | 1996 |
| International Mechanical Services Ltd | Construction | 2016 |
| Interopen Community Interest Company | Information & communication | 2018 |
| Intescene Ltd | Information & communication | 2026 |
| Intext Automotive Ltd | Professional & scientific | 2026 |
| Intfood Ltd | Wholesale & retail | 2021 |
| Into Training Ltd | Professional & scientific | 2013 |
| Intrepid Hermit Limited | Real estate | 2013 |
| Intyre Building Solutions Ltd | Construction | 2016 |
| Inventorybase Ltd | Professional & scientific | 2016 |
| Invictus Construction Southern Ltd | Construction | 2025 |
| Invictus Mechanical Group Ltd | Construction | 2018 |
| Invictus Professional Training Ltd | Education | 2017 |
| Invigorate Properties Ltd | Real estate | 2013 |
| Invision Services Limited | Health & social care | 2021 |
| Ioai Global Ltd | Education | 2025 |
| IOJ Services Ltd | Transport & logistics | 2021 |
| ION Property Ltd | Extraterritorial | 2024 |
| Ioncology Solutions Ltd | Health & social care | 2024 |
| Ionica Cleaning Services Ltd | Administrative & support | 2019 |
| IOW Padel Club Ltd | Arts & recreation | 2026 |