| Inglis Inglis Limited | Professional & scientific | 2015 |
| Inicio SIX Limited | Wholesale & retail | 2022 |
| Inimas Limited | Wholesale & retail | 2024 |
| Inkleya Ltd | Construction | 2025 |
| Inks of Essex Limited | Arts & recreation | 2023 |
| Inner Journey Counselling Services Ltd | Health & social care | 2024 |
| Innovation Consultancy Services Limited | Real estate | 2023 |
| Innovation Engineering Ltd | Manufacturing | 2022 |
| Innovative Carpentry Solutions Limited | Construction | 2023 |
| Innovative Logical Solutions Ltd | Information & communication | 2010 |
| Inovatixai Ltd | Information & communication | 2025 |
| Inox Construction Ltd | Construction | 2011 |
| Inpsychful Ltd | Health & social care | 2019 |
| Insco Limited | Administrative & support | 2000 |
| Inside & OUT Building and Maintenance Ltd | Construction | 2025 |
| Inside OUT Effect Limited | Administrative & support | 2019 |
| Insideout Coaching and Consulting Ltd | Administrative & support | 2025 |
| Insight Support Group Ltd | Health & social care | 2021 |
| Insighta Connect Limited | Real estate | 2024 |
| Insika Ltd | Professional & scientific | 2025 |
| Inspiration Youth Call Limited | Education | 2008 |
| Inspired Hope Events Limited | Extraterritorial | 2010 |
| Inspired People Development Limited | Professional & scientific | 2024 |
| Inspiring Social Work Ltd | Health & social care | 2021 |
| Installation Machinery Services Ltd | Manufacturing | 2024 |
| Installing UN Limited | Construction | 2016 |
| Instant Breaks Limited | Administrative & support | 2018 |
| Institute of Community Safety | Information & communication | 2002 |
| Insulated - Vent Ltd | Manufacturing | 2020 |
| Insytz Ltd | Administrative & support | 2025 |
| Intaflo Plumbing & Mechanical Services Limited | Construction | 2023 |
| Integral Cloud Limited | Information & communication | 2020 |
| Integridad Ltd | Wholesale & retail | 2007 |
| Integrity Drylining Limited | Construction | 2017 |
| Intelligent Construction Services Ltd | Construction | 2022 |
| Intelligent Properties Group Ltd | Real estate | 2022 |
| Intellirend Ltd | Construction | 2022 |
| Intercounty Farmers Limited | Transport & logistics | 1983 |
| Interesting Automation Solutions Limited | Professional & scientific | 2020 |
| Interior Construction Projects Limited | Construction | 2021 |
| International Brands Group UK Ltd | Manufacturing | 2021 |
| International OPS Limited | Administrative & support | 2018 |
| International Software Trade Ltd | Information & communication | 2021 |
| Interscope Limited | Professional & scientific | 2024 |
| Intertrans (Cargo Services) Limited | Transport & logistics | 1978 |
| Intexal Ltd | Wholesale & retail | 2012 |
| Intricate Creations Ltd | Manufacturing | 2010 |
| Intu Services Ltd | Other services | 2017 |
| Intumescent Coating Solutions Ltd | Administrative & support | 2018 |
| Invence Limited | Construction | 2019 |
| Inventive Patents Limited | Wholesale & retail | 2011 |
| Invicta Project Support Limited | Professional & scientific | 2026 |
| Invonext Ltd | Extraterritorial | 2015 |
| Ioana Ltd | Transport & logistics | 2021 |
| ION Bogdan Ltd | Construction | 2026 |
| Iordering Ltd | Wholesale & retail | 2021 |
| IP Services Essex Limited | Other services | 2013 |
| Ipercom Limited | Information & communication | 2008 |
| IPI Services 2017 Ltd. | Transport & logistics | 2017 |
| IPL22 Ltd | Construction | 2022 |
| IPP Analytics Limited | Health & social care | 2014 |
| Iqcomms Ltd | Information & communication | 2021 |
| IR Raza Spice Fusion Ltd | Hospitality | 2022 |
| Irma's Limited | Hospitality | 2004 |
| Ironmongerydirect Limited | Wholesale & retail | 1995 |
| IS Install Ltd | Construction | 2024 |
| Isabel the House of Jewels Ltd | Wholesale & retail | 2025 |
| ISD Mechanical Ltd | Construction | 2024 |
| Iseal Ltd | Construction | 2021 |
| Isee Services Limited | Other services | 2025 |
| Island Building & Landscaping Limited | Construction | 2021 |
| Islay Finance Limited | Financial services | 2020 |
| Ismael Construction Ltd | Construction | 2021 |
| Ismay Asbestos Services Ltd | Water & waste | 2021 |
| Isocialcircle Limited | Other services | 2017 |
| Ison Ltd | Transport & logistics | 2025 |
| Ispat Limited | Real estate | 2021 |
| Ispir Kebab Ltd | Hospitality | 2025 |
| IT Support Greater London Limited | Information & communication | 2014 |
| It's Overproof Ltd | Wholesale & retail | 2022 |
| ITC Services Limited | Administrative & support | 2004 |
| ITD Fire and Security Ltd | Administrative & support | 2023 |
| Itnationals Limited | Information & communication | 2025 |
| ITQ Salesforce Consulting Ltd | Information & communication | 2024 |
| Itrust Ltd | Administrative & support | 2017 |
| Itsa Limited | Information & communication | 1992 |
| Itype IT Limited | Information & communication | 2025 |
| Iustin 2010 Ltd | Transport & logistics | 2018 |
| IV Construction Ltd | Construction | 2025 |
| Ivanel Limited | Transport & logistics | 2022 |
| Iveco Holdings Limited | Financial services | 1967 |
| Iveco Limited | Wholesale & retail | 1986 |
| Iveco Pension Fund for Senior Staff Trustee Limited | Other services | 2007 |
| Iveco Pension Trustee Limited | Financial services | 1994 |
| Iveco Retail Limited | Wholesale & retail | 2013 |
| Ivell Motorsports Limited | Other services | 2023 |
| IVY Gate Court Management Company Limited | Other services | 2004 |
| IVY Jewellers Ltd | Manufacturing | 2016 |
| IW Hosking Investments Limited | Real estate | 2018 |
| Iwork Recruitment Limited | Administrative & support | 2020 |