| ICU Optics Limited | Wholesale & retail | 2014 |
| ICU Security Solutions(Uk) Limited | Administrative & support | 2010 |
| ICU Services Group Limited | Administrative & support | 2017 |
| Icybyamon Ltd | Other services | 2021 |
| ID Construction Design Ltd | Construction | 2017 |
| ID Surveys Ltd | Professional & scientific | 2011 |
| ID Ventures Limited | Professional & scientific | 2020 |
| IDA Active Limited | Wholesale & retail | 2024 |
| Idac Interiors Limited | Construction | 2014 |
| IDC Group Ltd | Professional & scientific | 2026 |
| Idea Construction Ltd | Construction | 2023 |
| Ideal Building & Joinery Services Limited | Construction | 2014 |
| Ideal Career Ltd | Information & communication | 2021 |
| Ideal Construction Limited | Construction | 1999 |
| Ideal Distributions Leic Ltd | Wholesale & retail | 2023 |
| Ideal Group of Companies Ltd | Information & communication | 2022 |
| Ideal Heating & GAS Ltd | Construction | 2017 |
| Ideal Infrastructure Ltd | Real estate | 2023 |
| Ideal Laundrette Ltd | Other services | 2025 |
| Ideal Properties (Leicester) Limited | Real estate | 1997 |
| Ideal Solutions Media and Technology Ltd | Information & communication | 2021 |
| Ideal Surgery Limited | Health & social care | 2021 |
| Ideal Trade Ltd | Construction | 2022 |
| Ideas Global Train Control Engineering Ltd | Administrative & support | 2018 |
| Idelegbagbonvictor Limited | Transport & logistics | 2022 |
| Ident Machines Limited | Manufacturing | 1978 |
| Ideo Design Limited | Manufacturing | 2013 |
| Idol Collection Limited | Construction | 2021 |
| Idontloveyouanymore Ltd | Arts & recreation | 2023 |
| Idrys Holdings Ltd | Financial services | 2026 |
| Idyllic Bespoke Joinery Ltd | Construction | 2017 |
| Iegb Limited | Real estate | 2022 |
| IES (Holdings) Limited | Administrative & support | 2010 |
| Ievolve Consultancy Ltd | Professional & scientific | 2026 |
| IF Bakery Ltd | Hospitality | 2024 |
| IF Bathrooms & Kitchens Ltd | Construction | 2014 |
| IF Fashions Ltd | Manufacturing | 2019 |
| IF Lettings Ltd | Real estate | 2024 |
| IF Locums Limited | Health & social care | 2014 |
| IF Logistic Ltd | Wholesale & retail | 2022 |
| IFA Transport Limited | Transport & logistics | 2021 |
| Ifab Services Ltd | Real estate | 2018 |
| Ifabs Global Limited | Education | 2017 |
| IFI Tech Ltd | Information & communication | 2026 |
| Ifisco Ltd | Manufacturing | 2025 |
| Ifix 360 Limited | Other services | 2019 |
| Ifix Roofing Ltd | Construction | 2025 |
| Ifly+ Limited | Administrative & support | 2014 |
| Iform Ltd | Professional & scientific | 2018 |
| Ifuniture Ltd | Wholesale & retail | 2026 |
| IG DPO Limited | Information & communication | 2024 |
| IG Health Limited | Information & communication | 2018 |
| IGD Solutions Ltd | Construction | 2022 |
| IGF Consultancy Ltd | Professional & scientific | 2021 |
| Ignis Engineering Ltd | Professional & scientific | 2023 |
| Ignite & Accelerate Ltd | Professional & scientific | 2018 |
| Ignite Creative Campaigns Ltd | Professional & scientific | 2025 |
| Ignite Curiosity Ltd | Information & communication | 2026 |
| Ignite Digital Limited Liability Partnership | | 2024 |
| Ignite Football Academy Limited | Education | 2025 |
| Ignite Powerhouse Ltd | Manufacturing | 2020 |
| IGS Elite Ltd | Construction | 2023 |
| IGS Solutions Limited | Information & communication | 2008 |
| Iguru Software Limited | Information & communication | 2015 |
| IH Scunthorpe Ltd | Hospitality | 2018 |
| IHD Medical Ltd | Health & social care | 2018 |
| Ihestates Limited | Real estate | 2022 |
| IHS Investments Ltd | Real estate | 2026 |
| IHS Rhomix Ltd | Hospitality | 2025 |
| Ihsan Way | Health & social care | 2024 |
| IHT Limited | Wholesale & retail | 2023 |
| Ihtw Ltd | Information & communication | 2019 |
| IHU Investments Ltd | Real estate | 2022 |
| Ihya AL Uloom | Education | 2021 |
| Iiceo Limited | Wholesale & retail | 2023 |
| IIK Investments Ltd | Real estate | 2025 |
| IIR Services (UK) Limited | Energy | 2014 |
| IIT Ltd | Other services | 2025 |
| IJ Inventories Ltd | Households | 2024 |
| Ijdegreat Ltd | Information & communication | 2021 |
| IJN Apparel Limited | Wholesale & retail | 2026 |
| IJY Measurement Services Ltd | Professional & scientific | 2017 |
| IK Accounts Limited | Wholesale & retail | 2023 |
| IK Assets Limited | Real estate | 2023 |
| IK Clinics Limited | Real estate | 2022 |
| IK Logistics and Trading Ltd | Wholesale & retail | 2026 |
| IKA Property Services Ltd | Construction | 2024 |
| Ikalon U.K. Limited | Administrative & support | 1992 |
| Ikamin Technology Limited | Extraterritorial | 2024 |
| Ikaw Care Ltd | Health & social care | 2024 |
| Ikfa Foods Ltd | Wholesale & retail | 2023 |
| Ikfa Ltd | Wholesale & retail | 2020 |
| IKI Limited | Information & communication | 2013 |
| Iknorant Ltd | Health & social care | 2023 |
| Ikonetu Technology Limited | Information & communication | 2026 |
| IKS Motors PVT Ltd | Wholesale & retail | 2026 |
| Ikstar Bathrooms and Kitchens Limited | Manufacturing | 2022 |
| Ikstar Limited | Wholesale & retail | 2015 |
| ILA Ramaiya Properties Ltd | Real estate | 2023 |
| Ilak Service Ltd | Health & social care | 2025 |