| Illyrian Grooming Studio Ltd | Other services | 2025 |
| Ilsc London Ltd | Professional & scientific | 2014 |
| IM Safeguarding Ltd | Education | 2018 |
| IMA Constructions London Limited | Construction | 2016 |
| Image Ceilings Limited | Construction | 1988 |
| Imagine Tailor Made Travel Ltd | Administrative & support | 2018 |
| Imcd UK Acquisitions Limited | Professional & scientific | 2010 |
| Imcd UK Limited | Wholesale & retail | 1988 |
| Imee Ltd | Construction | 2026 |
| Immersion VR Studios Limited | Arts & recreation | 2025 |
| Imperial Business Services (UK) Limited | Administrative & support | 2014 |
| Imperial Freight Nigeria Limited | Transport & logistics | 1998 |
| Imperial Homecare Limited | Other services | 2014 |
| Imperial Landscapes Limited | Professional & scientific | 2014 |
| Imperial World Ltd | Real estate | 1997 |
| Imperium Secure Services Limited | Administrative & support | 2023 |
| Impersand Ltd | Information & communication | 2014 |
| Implivia Limited | Information & communication | 2026 |
| Impress Recruitment Services Limited | Administrative & support | 2006 |
| Impress Removals & Storage Ltd | Transport & logistics | 2021 |
| Impress Removals Ltd | Transport & logistics | 2022 |
| Imran City 786 Limited | Wholesale & retail | 2020 |
| Imst London Limited | Wholesale & retail | 2018 |
| Imtoled World Global Ventures Limited | Wholesale & retail | 2024 |
| Imuka Ltd. | Education | 2014 |
| IN Digital Entertainment Ltd | Extraterritorial | 2025 |
| IN Fieri Ltd | Professional & scientific | 2026 |
| In-Vent Environmental Services Limited | Construction | 2019 |
| Inamorata Ltd | Information & communication | 2010 |
| Index Match Solutions Ltd | Information & communication | 2025 |
| India Cottage (Surrey) Limited | Hospitality | 2009 |
| India India Whitton Ltd | Hospitality | 2020 |
| Indigo Coulsdon Ltd | Real estate | 2026 |
| Indigo Oxshott Ltd | Real estate | 2025 |
| Indigo Park Trading Company Ltd | Wholesale & retail | 2020 |
| Indigo Ridge Effingham Ltd | Construction | 2022 |
| Indigo Sanderstead Ltd | Real estate | 2026 |
| Indiraaj Business & Management Solutions Ltd | Professional & scientific | 2017 |
| Indivirtus Healthcare Services Limited | Professional & scientific | 2021 |
| Indoor Vapour Limited | Financial services | 2014 |
| Indu Properties Limited | Real estate | 2011 |
| Indus Trader Ltd | Wholesale & retail | 2022 |
| Indus Valley Labs Limited | Information & communication | 2017 |
| Industrial Trucks Training Limited | Education | 2023 |
| Infi UK Limited | Information & communication | 2005 |
| Infinite Furniture Solutions Ltd | Manufacturing | 2018 |
| Infinite Strategy Limited | Professional & scientific | 2022 |
| Infinite Strategy Real Estate Limited | Real estate | 2026 |
| Infinitive Properties Limited | Real estate | 2020 |
| Infinity Eco Build SWC Ltd | Real estate | 2019 |
| Infinity Group Services Co Ltd | Construction | 2026 |
| Infinity Heating Solutions Ltd | Construction | 2021 |
| Infinity Land Wealth Ltd | Education | 2025 |
| Infinity Nails (SM) Limited | Other services | 2019 |
| Infinity Private Limited | Financial services | 2023 |
| Infix Installations Limited | Construction | 2016 |
| Information Mechanics Limited | Information & communication | 2002 |
| Informed Insights Limited | Information & communication | 2025 |
| Informing Decisions Ltd | Professional & scientific | 2021 |
| Infotech Advisory Group Ltd | Information & communication | 2025 |
| Infrastructure Consultancy Services Ltd | Administrative & support | 2006 |
| Infrativity Ltd | Professional & scientific | 2019 |
| Ingenium Global Ltd | Professional & scientific | 2010 |
| Iniko House of Prints Ltd | Manufacturing | 2020 |
| Inko Foods Ltd | Hospitality | 2016 |
| Inkspell Limited | Information & communication | 1996 |
| Inner Thread Ltd | Arts & recreation | 2022 |
| Innomax Company Limited | Professional & scientific | 2022 |
| Innova Software Group Ltd | Information & communication | 2022 |
| Innovate ED Ltd | Education | 2023 |
| Innovix Solutions Ltd | Transport & logistics | 2018 |
| Innspire PUB Company Ltd | Hospitality | 2025 |
| Inpartnership Recruitment Limited | Administrative & support | 2021 |
| INS Building Ltd | Construction | 2022 |
| Inside & Outside Sutton Ltd | Wholesale & retail | 2026 |
| Inspiral Design Ltd | Manufacturing | 2008 |
| Inspiri Limited | Arts & recreation | 2006 |
| Inspiron London Limited | Health & social care | 2018 |
| Institute of Hospitality | Other services | 1949 |
| INSURE2BSURE Ltd | Financial services | 2012 |
| Intec Education Ltd | Education | 2012 |
| Intech Trading Ltd | Real estate | 2013 |
| Intego Services Ltd | Construction | 2026 |
| Integrated Care Services Ltd | Health & social care | 2018 |
| Integrated London Limited | Construction | 2022 |
| Integration Factory Ltd | Information & communication | 2018 |
| Integrity Infotech Limited | Information & communication | 2010 |
| Inteli-Scan Software Solutions Ltd | Information & communication | 2025 |
| Intelligent Systems Limited | Information & communication | 1995 |
| Intellilogix Ltd | Information & communication | 2025 |
| Intelliwitz Limited | Information & communication | 2019 |
| Inteltics Ltd | Information & communication | 2018 |
| Interface Specialist Care Limited | Health & social care | 2011 |
| International Border Management and Technologies Association Ltd | Other services | 2017 |
| Interop Solutions Ltd | Construction | 2015 |
| Intersaga Literary Agency Ltd | Information & communication | 2024 |
| Intersect Solutions Ltd | Information & communication | 2011 |
| Intiqa Ltd | Administrative & support | 2019 |
| Intrepid Security Solutions Limited | Construction | 1993 |
| Intrepid Security UK Ltd | Construction | 2025 |