| IN Queer Company Limited | Wholesale & retail | 2025 |
| Inbroider Ltd | Wholesale & retail | 2021 |
| Incredible Bharat Ltd | Hospitality | 2019 |
| Indeep Vision Limited | Health & social care | 2024 |
| Indegu Ltd | Information & communication | 2018 |
| Indentec Hardness Testing Machines Limited | Manufacturing | 1976 |
| Independent Diving Equipment Services and Training Ltd. | Education | 2011 |
| Independent Social Work & Immigration Consultancy Ltd | Health & social care | 2026 |
| Indigo Mortgages Ltd | Professional & scientific | 2020 |
| Individual Tailoring Limited | Wholesale & retail | 1965 |
| Indoor and Outdoor Catering Ltd | Hospitality | 2023 |
| Industeel UK Limited | Manufacturing | 1989 |
| Industrial Phycology Limited | Water & waste | 2012 |
| Industrial Pipework and Heating Enterprises Limited | | 1967 |
| Industrial Trading Company Limited | Wholesale & retail | 1958 |
| Industry Aggregates Limited | Construction | 2017 |
| Inference Chain Limited | Information & communication | 2026 |
| Inference Group Ltd | Information & communication | 2024 |
| Inflowstructure Limited | Information & communication | 2025 |
| Infor Limited | Professional & scientific | 1994 |
| Infrastructure Advisory UK Limited | Professional & scientific | 2015 |
| Ingenious Group Holdings Limited | Professional & scientific | 2004 |
| Ingenious Locks & Hardware Limited | Wholesale & retail | 2014 |
| Ingenium CNC Specialists and Solutions Limited | Professional & scientific | 2024 |
| Ingot-Green Ltd | Information & communication | 2023 |
| Inhaus Design Ltd | Construction | 2004 |
| Inia AI Ltd | Information & communication | 2024 |
| Inkalab Ltd | Professional & scientific | 2024 |
| Inkberrow Physiotherapy & Acupuncture Ltd | Other services | 2020 |
| Inkberrow Services Limited | Administrative & support | 2015 |
| Inkcore Limited | Wholesale & retail | 2025 |
| INNOVATED4.0 Ltd | Professional & scientific | 2024 |
| Innovative Packaging Ltd | Extraterritorial | 2023 |
| Innovative Psychiatric Services Ltd | Health & social care | 2025 |
| INOV8 Build & Design Ltd | Construction | 2016 |
| Inrelation Limited | Extraterritorial | 2026 |
| Inrsc Limited | Professional & scientific | 2019 |
| Insert Audio Limited | Administrative & support | 2006 |
| Insertech Ltd | Professional & scientific | 2025 |
| Insight Quantum Expert Services Limited | Professional & scientific | 2026 |
| Insight Works Coaching Ltd | Administrative & support | 2020 |
| Inspirational Care CIC | Health & social care | 2025 |
| Inspirational Kids Ltd | Arts & recreation | 2011 |
| Inspire Education Learning Ltd | Education | 2015 |
| Inspired Ideas Design Co. Ltd | Information & communication | 2023 |
| Inspired Personal Training Limited | Arts & recreation | 2005 |
| Inspiring Accessories Ltd | Wholesale & retail | 2011 |
| Inspiring Group Holdings Limited | Professional & scientific | 2019 |
| Inspiring Group Limited | Professional & scientific | 2025 |
| Inspiring People Limited | Education | 2000 |
| Inspirit Productions Ltd | Information & communication | 2017 |
| Instant Scenery Ltd | Administrative & support | 2018 |
| Integrated Business Travel Limited | Administrative & support | 1992 |
| Integrated Engineering Services Limited | Professional & scientific | 2004 |
| Integrated Industries Limited | Information & communication | 2023 |
| Intelecomm (UK) Limited | Information & communication | 2002 |
| Intelligence Stack Limited | Information & communication | 2026 |
| Intelligent Abodes Ltd | Construction | 2026 |
| Intellitect Water Limited | Other services | 2005 |
| Inter-Fix Interiors UK Ltd | Construction | 2006 |
| Interim Finance Solutions Limited | Professional & scientific | 2012 |
| Interim Operations Leadership Ltd | Professional & scientific | 2020 |
| Interlay Driveways & Patios Ltd | Construction | 2024 |
| Interlay Driveways Ltd | Construction | 2014 |
| Interlay Roofing Services Ltd | Construction | 2023 |
| Interlink Engineering Solutions (IES) Limited | Professional & scientific | 2026 |
| Intermedia Film Distribution 2004 Limited | Arts & recreation | 2004 |
| International Red Flare Limited | Professional & scientific | 2011 |
| International UK Store Limited | Wholesale & retail | 2026 |
| International Wireless Ltd | Information & communication | 2012 |
| Internet Nominees Limited | Professional & scientific | 2018 |
| Introsmart Ltd | Administrative & support | 2011 |
| Intrusion Festival Ltd | Arts & recreation | 2025 |
| Intuitive Plus Limited | Professional & scientific | 2005 |
| Investaste Limited | Manufacturing | 2024 |
| Investments AA UK Ltd | Manufacturing | 2020 |
| Ionracas Limited | Other services | 2023 |
| Ionut Puscasu Services Limited | Transport & logistics | 2019 |
| IP Express Logistics Ltd | Transport & logistics | 2022 |
| IP Usergroup International Limited | Professional & scientific | 2018 |
| IP3 Limited | Information & communication | 2009 |
| Ipak Integrated Packaging Solutions Limited | Transport & logistics | 2008 |
| Ipcds Ltd | Transport & logistics | 2015 |
| Iperium Consulting Holdings Limited | Professional & scientific | 2013 |
| Iperium Consulting Limited | Administrative & support | 2006 |
| Iperium Property Limited | Real estate | 2021 |
| IQL UK Limited | Education | 1999 |
| Iren Construction Limited | Construction | 2026 |
| Iris Print Limited | Information & communication | 2015 |
| Iron Fight Club Ltd | Arts & recreation | 2018 |
| Iron Throne Limited | Hospitality | 2018 |
| Ironbridge Railway Trust | Transport & logistics | 2007 |
| Ironshare Ltd | Information & communication | 2016 |
| IRR Simulators Ltd | Wholesale & retail | 2020 |
| Isabella George Capital Ltd | Real estate | 2024 |
| Isaia Clean 28 Ltd | Administrative & support | 2025 |
| Isambard Digital Media Ltd | Information & communication | 2007 |
| Iskomed UK Limited | Wholesale & retail | 2024 |
| Isla Components Limited | Manufacturing | 1993 |
| Isle of Wight Whisky Limited | Manufacturing | 2023 |