| Innovation On-Site Limited | Construction | 2007 |
| Innovation Scaffolding Ltd | Administrative & support | 2017 |
| Innovative Endeavours Limited | Information & communication | 2021 |
| Innovative Medical Solutions Limited | Health & social care | 2024 |
| Innsdependent Housing Limited | Real estate | 2019 |
| INS and Outs Finance Ltd | Professional & scientific | 2026 |
| INS Football Ltd | Professional & scientific | 2026 |
| INS Group Holdings Limited | Financial services | 2023 |
| INS Management Ltd | Administrative & support | 2017 |
| INS Management Womens Sport Ltd | Professional & scientific | 2024 |
| INS Portugal Limited | Professional & scientific | 2023 |
| Inscape Estates Ltd | Real estate | 2024 |
| Inseal Electrical Limited | Construction | 2022 |
| Insentra Limited | Administrative & support | 1999 |
| Insight Connected Limited | Other services | 2025 |
| Insight Facades (Service & Maintenance) Limited | Construction | 2016 |
| Insight Facades Direct Limited | Construction | 2018 |
| Insight Facades Limited | Construction | 2013 |
| Insight IT Simplified Ltd | Information & communication | 2020 |
| Insight Management Solutions Limited | Professional & scientific | 2002 |
| Insofti Mart Ltd | Wholesale & retail | 2023 |
| Insound Music Ltd | Information & communication | 2026 |
| Inspira Furniture Ltd | Manufacturing | 2020 |
| Inspira Group Ltd | Manufacturing | 2017 |
| Inspira Homes Ltd | Construction | 2020 |
| Inspira IB Ltd | Manufacturing | 2022 |
| Inspira VM Ltd | Manufacturing | 2023 |
| Inspirati Limited | Professional & scientific | 2011 |
| Inspire Supported Living Limited | Administrative & support | 2019 |
| Inspired Creations by ZOE Limited | Wholesale & retail | 2025 |
| Inspired Life Community Interest Company | Administrative & support | 2010 |
| Inspired Refits Ltd | Construction | 2024 |
| Inspiring Blues Ltd | Other services | 2020 |
| Inspiring Futures Social Care Consultancy Ltd | Other services | 2025 |
| Instagrab Limited | Transport & logistics | 2020 |
| Install Direct London Limited | Construction | 2013 |
| Instant Assist Ltd | Other services | 2021 |
| Institute of Data Privacy Practitioners | Extraterritorial | 2005 |
| Institution of Agricultural Engineers(The) | Other services | 1960 |
| Insulation Kits Limited | Wholesale & retail | 2023 |
| Insure Your Trip Limited | Extraterritorial | 2009 |
| Insync Lettings Ltd | Real estate | 2019 |
| Integra Property UK Limited | Real estate | 2006 |
| Integrated Homes Limited | Professional & scientific | 1997 |
| Integrated Power Group Ltd | Professional & scientific | 2026 |
| Integrated Radio Systems Ltd | Information & communication | 2005 |
| Integritest Limited | Construction | 2020 |
| INTEGRITY2INSIGHT Ltd | Professional & scientific | 2010 |
| Integrum Build Ltd | Construction | 2024 |
| Integrum Ventures Ltd | Real estate | 2024 |
| Intellectual Collaboration Ltd | Information & communication | 2020 |
| Intelligencia Training Limited | Education | 2013 |
| Intelligent Business Consulting Services Ltd | Information & communication | 2016 |
| Intelligent Property Sourcing Ltd | Real estate | 2025 |
| Intelligent Supply Systems Limited | Information & communication | 2015 |
| Intellimpact Limited | Education | 2024 |
| Inter PAT Testing Ltd | Manufacturing | 2020 |
| Interact Training Solutions Limited | Professional & scientific | 2005 |
| Interamp Ltd | Professional & scientific | 2010 |
| Interfoam Group Limited | Manufacturing | 2023 |
| Interfoam Limited | Manufacturing | 1992 |
| Interior Base Limited | Wholesale & retail | 2018 |
| Interior Fitters Limited | Construction | 2022 |
| Interior Mechanica Ltd | Extraterritorial | 2024 |
| Interiorexterior Limited | Other services | 2018 |
| Interiors by George Short Limited | Wholesale & retail | 2013 |
| Interlink Security Services UK Limited | | 2009 |
| Intermedia Global Group Limited | Financial services | 2024 |
| Intermedia Global Limited | Professional & scientific | 2021 |
| Intermedia Global Marketing Limited | Administrative & support | 2019 |
| International Aerospace Engineering Limited | Manufacturing | 2003 |
| International House of Prayer Limited | Other services | 2007 |
| International Law Connection Ltd | Professional & scientific | 2011 |
| International Mini Market Ltd | Wholesale & retail | 2020 |
| International Quality Imports and Exports Ltd | Wholesale & retail | 2020 |
| International Standardized Testing Organization Limited | Other services | 2019 |
| Internazionale Engineering Ltd | Professional & scientific | 2019 |
| Interphase Interiors Ltd | Administrative & support | 2007 |
| Intersectionality Womens Programmes CIC | Education | 2023 |
| Intexture Design Home & Office Ltd | Construction | 2024 |
| Intexture Homes Ltd | Health & social care | 2025 |
| Intoku Ltd | Arts & recreation | 2018 |
| Intqual-Pro Limited | Professional & scientific | 2014 |
| Intricate IT Limited | Other services | 2020 |
| Intrinsic Robotics Limited | Professional & scientific | 2025 |
| Intuition Legacy Limited | Arts & recreation | 2024 |
| Inusisi Ltd | Wholesale & retail | 2024 |
| Investcope Ltd | Professional & scientific | 2009 |
| Investdune Limited | Professional & scientific | 1997 |
| Invicta House Properties Ltd | Real estate | 2021 |
| Invictus Sports Gym Ltd | Arts & recreation | 2025 |
| Invictus Supply Limited | Wholesale & retail | 2025 |
| Invincible Sounds Ltd | Arts & recreation | 2025 |
| Iofee Limited | Administrative & support | 2025 |
| IOG Capital Partners Ltd | Real estate | 2024 |
| ION Bridge Limited | Real estate | 2019 |
| Iona Shore Limited | Real estate | 1955 |
| Ionic Consultant Ltd | Information & communication | 2022 |
| Ionutroman Construction Ltd | Construction | 2019 |
| Ioptex Ltd | Health & social care | 2025 |