| Impactfield Limited | Professional & scientific | 2024 |
| Impactprizes.Com Limited | Other services | 2024 |
| Imperial Consultancy Services Ltd | Professional & scientific | 2024 |
| Imperial Engineering Group Limited | Financial services | 2021 |
| IN and OUT Rigging Ltd | Construction | 2025 |
| IN Motion Consulting Ltd | Professional & scientific | 2022 |
| Incloud Digital & Data Ltd | Information & communication | 2014 |
| Incompass IP Europe Limited | Administrative & support | 2007 |
| IND Contractors Ltd | Administrative & support | 2019 |
| Indchem Ltd | Wholesale & retail | 2024 |
| Independent Hrit Solutions Ltd | Wholesale & retail | 2017 |
| Indigo Design and Build London Ltd | Construction | 2023 |
| Industrial Tool Supplies (London) Limited | Wholesale & retail | 1979 |
| Industrial Tool Supplies Group Limited | Wholesale & retail | 2023 |
| Inedia Limited | Construction | 2016 |
| Inese Weymouth Ltd | Other services | 2016 |
| Infinite Heating & Plumbing Ltd | Construction | 2022 |
| Infinity Building Contractors (London) Limited | Construction | 2017 |
| Infinity Pharmaceuticals Limited | Wholesale & retail | 2003 |
| Influensa Solutions Marketing Ltd | Information & communication | 2026 |
| Info Creative Building Services Ltd | Manufacturing | 2026 |
| Infoda ERP & Software Ltd | Information & communication | 2025 |
| Informed Finance Limited | Wholesale & retail | 2013 |
| Infradep IT Consulting Ltd | Information & communication | 2025 |
| Infront Supply Limited | Administrative & support | 2004 |
| Infynix Limited | Information & communication | 2025 |
| Inga VIP Cleaning Ltd | Construction | 2025 |
| Ingenious IT Professionals Ltd | Information & communication | 2023 |
| Ingram Building Ltd | Construction | 2025 |
| Ingrebourne Harmondsworth Limited | Real estate | 2023 |
| Ingrebourne Kemps Limited | Real estate | 2020 |
| Ingrebourne PFA Ltd | Mining & quarrying | 2016 |
| Ingrebourne Valley Holdings Ltd | Financial services | 2012 |
| Inheritance Ltd | Administrative & support | 2003 |
| Inioluwa Healthcare Services Ltd | Health & social care | 2023 |
| Injection Specialist Ltd | Manufacturing | 2019 |
| Injector Sale Ltd | Wholesale & retail | 2021 |
| Inme Organics Ltd | Wholesale & retail | 2024 |
| Innerflow Method Limited | Professional & scientific | 2018 |
| Inno Autos Ltd | Wholesale & retail | 2025 |
| Innova Art Limited | Manufacturing | 2003 |
| Innova Brands Limited | Wholesale & retail | 2016 |
| Innovate Property Group Ltd | Real estate | 2023 |
| Innovation Brickwork Limited | Construction | 2019 |
| Innovation Management Solutions Limited | Information & communication | 2012 |
| Innovation Technology Coatings Limited | Manufacturing | 2013 |
| Inns Cleaning Services Limited | Other services | 2013 |
| Innsight Cleaning Services Ltd | Administrative & support | 2026 |
| Innyorey Limited | Professional & scientific | 2013 |
| Inotrans Limited | Transport & logistics | 2017 |
| Insideecommerce Ltd | Wholesale & retail | 2024 |
| Insight Tech Ltd | Information & communication | 2014 |
| Insightleverage Limited | Information & communication | 2023 |
| Insights International Ltd | Wholesale & retail | 2025 |
| Insights Mint Solutions Ltd | Wholesale & retail | 2026 |
| Inspire Apparel Ltd | Wholesale & retail | 2023 |
| Inspire Growth and Development Initiative Ltd | Education | 2021 |
| Inspired Health Global Ltd | Professional & scientific | 2023 |
| Instant Locum Ltd | Health & social care | 2022 |
| Instarepairuk Ltd | Wholesale & retail | 2020 |
| Institute of Videography | Other services | 1991 |
| Integrated Professionals Limited | Wholesale & retail | 2019 |
| Integration Support Limited | Education | 2007 |
| Integrity Healthcare Group Limited | Health & social care | 2024 |
| Intel Mechanics Ltd | Wholesale & retail | 2025 |
| Intellijsosa Consulting Limited | Information & communication | 2019 |
| Intent Group Ltd | Administrative & support | 2016 |
| Intenttech Limited | Information & communication | 2019 |
| Interdecima Consulting Ltd | Information & communication | 2022 |
| Interga London Ltd | Wholesale & retail | 2023 |
| Interior Plantings Limited | Administrative & support | 2006 |
| Interlock Ltd | Administrative & support | 2015 |
| Interlogistics Ltd | Transport & logistics | 2026 |
| International Centre of Contemporary Research in Islamic Sciences Ltd | Education | 2022 |
| International Management Leasing Development Ltd | Information & communication | 2026 |
| Interstyle Group Limited | Construction | 2000 |
| Intrinsic Fire Protection Limited | Construction | 2016 |
| Inuzi Medicare Limited | Health & social care | 2020 |
| Invester UK Ltd | Health & social care | 2012 |
| Investevolve Limited | Professional & scientific | 2008 |
| Investment Assets Ltd | Real estate | 2023 |
| Invictus Digital Limited | Information & communication | 2024 |
| Inviziderm Limited | Other services | 2022 |
| Inwoodink Limited | Other services | 2011 |
| Ioel Limited | Professional & scientific | 2026 |
| IOF Properties Ltd | Real estate | 2024 |
| Iona Francis Ltd | Administrative & support | 2022 |
| Ioreh Ltd | Other services | 2022 |
| IP Trans UK Ltd | Transport & logistics | 2017 |
| Ipexa Limited | Administrative & support | 2006 |
| Iplan Office Relocations Ltd | Transport & logistics | 2021 |
| IQ Solutions Limited | Professional & scientific | 2019 |
| Iquest Ltd | Construction | 2017 |
| Ireibus Ltd | Construction | 2021 |
| Ireloju Limited | Health & social care | 2025 |
| Iremicare Limited | Health & social care | 2023 |
| Iris Medicals Limited | Health & social care | 2024 |
| Iron Works (Cambridge) Management Company Limited | Households | 2019 |
| Ironclad Assets Ltd | Extraterritorial | 2026 |
| Irongate Services Ltd | Water & waste | 2026 |