| Ideal Care Services Limited | Health & social care | 2018 |
| Ideal Property Projects Ltd | Financial services | 2015 |
| Idealpoint Limited | Information & communication | 2002 |
| Identity Music Ltd | Information & communication | 2019 |
| Idig Earthworks Limited | Construction | 2019 |
| Ifour Solutions Limited | Information & communication | 2006 |
| Igloo Audio Limited | Wholesale & retail | 2006 |
| IH Carpentry Ltd | Construction | 2019 |
| IHG Solutions Ltd | Information & communication | 2014 |
| Il-Diy Burncraft Limited | Wholesale & retail | 2024 |
| Ilex Consulting Ltd | Real estate | 2005 |
| Illusion Design and Construct Limited | Arts & recreation | 2011 |
| Illusion Storage Limited | Real estate | 2023 |
| IM4U Ltd | Arts & recreation | 2024 |
| Imago Community | Health & social care | 2005 |
| Imakebleeps Ltd | Arts & recreation | 2026 |
| Imco Consultancy Ltd | Administrative & support | 2025 |
| Imijo Ltd | Wholesale & retail | 2009 |
| Impeccable Plumbers Ltd | Construction | 2021 |
| Improve Home Appeal Ltd | Construction | 2025 |
| Improvement Engine Ltd | Professional & scientific | 2024 |
| Imptech Limited | Manufacturing | 2020 |
| Imptech Press Engineering Ltd | Manufacturing | 2009 |
| Imzo Limited | Information & communication | 2016 |
| IN Practice Systems Limited | Information & communication | 1984 |
| IN Tech Jobs Ltd | Information & communication | 2018 |
| IN the White Room Limited | Professional & scientific | 2012 |
| Incide Corporate Consultants Limited | Professional & scientific | 1991 |
| Incide Limited | Professional & scientific | 2003 |
| Inclusion Inc. Ltd | Professional & scientific | 2021 |
| Inclusive.Io Ltd | Information & communication | 2021 |
| Incremental Marketing Limited | Professional & scientific | 2019 |
| Index Living Limited | Real estate | 2026 |
| Index Real Estate Ltd | Real estate | 2024 |
| Indiecomics.Co.Uk Community Interest Company | Arts & recreation | 2023 |
| Indielab Elevate Limited | Information & communication | 2023 |
| Indielab Investor Events Limited | Information & communication | 2022 |
| Indomitable Consultancy Ltd | Information & communication | 2011 |
| Indomitable Property Capital Limited | Real estate | 2025 |
| Indra Advisory Ltd | Professional & scientific | 2025 |
| Indrani Ltd | Hospitality | 2024 |
| Industry-Superstore Limited | Extraterritorial | 2020 |
| Inenel Limited | Real estate | 2024 |
| Inez Ltd | Other services | 2022 |
| Infinity Commercial Limited | Real estate | 2010 |
| Infinity Group Holdings Limited | Financial services | 2021 |
| Infinity Technology Solutions Limited | Information & communication | 2001 |
| Inflexion Group Ltd | Information & communication | 2021 |
| Information Matters Ltd | Administrative & support | 2024 |
| Infotron Solutions Limited | Information & communication | 2014 |
| Infoverve Ltd | Information & communication | 2025 |
| Ingenia Solutions Limited | Manufacturing | 2001 |
| Inhaus International Group LLP | | 2023 |
| Inhaus International Holdings Limited | Wholesale & retail | 2023 |
| Inhouse Support Projects Ltd | Construction | 2018 |
| Iniko Ltd. | Manufacturing | 2006 |
| INK Media a Public Relations Company Ltd | Professional & scientific | 2016 |
| Inkwood Bespoke Limited | Manufacturing | 2026 |
| Inner Balance Counselling Kent Ltd | Health & social care | 2024 |
| Inner Space Counselling Ltd | Health & social care | 2017 |
| Innfrant Ltd | Hospitality | 2019 |
| Innovate Lifts Ltd | Manufacturing | 2016 |
| Innovation Centre Europe Limited | Professional & scientific | 1978 |
| Innovations by Design Limited | Information & communication | 2000 |
| Innovative Brands Limited | Wholesale & retail | 2023 |
| Innovative Statistical Analysis and Publications Ltd | Professional & scientific | 2019 |
| Innovord Solutions Ltd | Information & communication | 2015 |
| Inoma Consulting Ltd | Professional & scientific | 2023 |
| Inovni UK Ltd | Information & communication | 2016 |
| INQ Holdings Ltd | Financial services | 2017 |
| Insafe International Limited | Manufacturing | 1984 |
| Insafe Limited | Administrative & support | 2001 |
| Insafe Management Ltd | Professional & scientific | 2013 |
| Insafe Manufacturing Limited | Manufacturing | 2004 |
| Insafe Security Limited | Manufacturing | 1937 |
| Inside & OUT Limited | Construction | 1995 |
| Inside NET Zero Ltd | Information & communication | 2024 |
| Insight Accounts Ltd | Professional & scientific | 2021 |
| Insight Information Ltd | Professional & scientific | 2020 |
| Insite Data Systems Limited | Information & communication | 2011 |
| Instrumental Media Rights Limited | Information & communication | 2015 |
| Insurance Compliance Services Limited | Financial services | 2002 |
| Integritas Financial Solutions Limited | Financial services | 2012 |
| Inteligans Ltd | Information & communication | 2021 |
| Intellectual Apps UK Ltd | Information & communication | 2022 |
| Intellectual Property Ventures Limited | Professional & scientific | 2016 |
| Intelligent HQ Limited | Information & communication | 2019 |
| Intelligent Real Estate DUE Diligence Limited | Financial services | 2010 |
| Intelligent Salon Software Ltd | Information & communication | 2012 |
| Interior Design Geek Limited | Professional & scientific | 2017 |
| International Care Services Limited | Professional & scientific | 1999 |
| International Centre for Eelam Tamil's Rights - UK | Other services | 2019 |
| International Copiers UK Limited | Other services | 1994 |
| International Volunteer Solutions Limited | Health & social care | 2014 |
| Interp-Ability Limited | Education | 2013 |
| Interpreters-On-Call Ltd | Information & communication | 2006 |
| Intramast (UK) Limited | Transport & logistics | 1996 |
| Intrepid BEE Limited | Financial services | 2008 |
| Intrepid Property Limited | Real estate | 2015 |
| Intuity Edge Limited | Administrative & support | 2016 |