| Infrastructure Asset Ownership Company Limited | Professional & scientific | 2012 |
| Ingleby (1977) Limited | Administrative & support | 2015 |
| Ingo Consulting Limited | Professional & scientific | 2017 |
| Inklein Consulting Limited | Information & communication | 2004 |
| Inner Ambition Ltd | Other services | 2017 |
| Innis ELM | | 2011 |
| Innosight Consultancy Limited | Information & communication | 2024 |
| Innovate Digital Limited | Information & communication | 2021 |
| Innovate Services Limited | Hospitality | 2007 |
| Innovation and Consulting Ltd | Information & communication | 2025 |
| Innovative Energy Systems Ltd | Construction | 2020 |
| Innovo Management Limited | Real estate | 2016 |
| Inova Group Ltd | Information & communication | 2020 |
| Inphtech Limited | Information & communication | 2010 |
| Inshallah Limited | Information & communication | 2010 |
| Inside OUT Consulting Limited | Administrative & support | 2006 |
| Insider Travel Services Limited | Administrative & support | 2017 |
| Insight Assured Ltd | Other services | 2004 |
| Insight FM Limited | Administrative & support | 2019 |
| Insightology.Ai Ltd | Information & communication | 2025 |
| Inspire 4 Design Limited | Construction | 2017 |
| Inspire Coaching and Performance Ltd | Education | 2024 |
| Inspire Kitchens Ltd | Wholesale & retail | 2018 |
| Inspire Upholstery Limited | Manufacturing | 2015 |
| Inspiring Destinations Ltd | Professional & scientific | 2015 |
| Inspiring Mexico Ltd | Professional & scientific | 2024 |
| Inspo Inno Ventures Ltd | Real estate | 2025 |
| Inspo Innovations Limited | Wholesale & retail | 2023 |
| Instant Surveys Ltd | Real estate | 2024 |
| Institute for Medicine Development Ltd | Administrative & support | 2014 |
| Instow Management Limited | Extraterritorial | 1996 |
| Insura Limited | Financial services | 2025 |
| Insure NED Search Ltd | Administrative & support | 2025 |
| INT Export Ltd | Real estate | 2020 |
| Integer Partners Ltd | Real estate | 2023 |
| Integra Independent Financial Planning Limited | Financial services | 1994 |
| Integra Law Ltd | Professional & scientific | 2017 |
| Integration SR Limited | Professional & scientific | 2026 |
| Integrative Geoscience Limited | Mining & quarrying | 2012 |
| Intelligent Air Conditioning Ltd | Energy | 2010 |
| Intelligent Computing Ltd | Information & communication | 2023 |
| Intelligrow Agriculture Ltd | Agriculture & fishing | 2021 |
| Inter-Active Gaming Ltd | Wholesale & retail | 2022 |
| Interests Media Ltd | Information & communication | 2014 |
| Intergenerational Music Making CIC | Health & social care | 2018 |
| Interim Marketing Solutions Limited | Administrative & support | 2010 |
| Interim Resource Solutions Ltd | Professional & scientific | 2009 |
| Interiorlux Ltd | Construction | 2013 |
| Interiors Idea Ltd | Construction | 2012 |
| International Centre of Children, Adolescents and Adults Psychology Ltd | Professional & scientific | 2019 |
| International Children's Care (UK) | Administrative & support | 2002 |
| International Clay Target Shooting Council Limited | Arts & recreation | 2005 |
| International Eco LC Limited | Education | 2023 |
| International Holdings Group Limited | Financial services | 2025 |
| International Hospitality Service Ltd. | Other services | 2017 |
| International HR Consulting Ltd | Administrative & support | 2013 |
| International James Jets Limited | Information & communication | 2023 |
| International Security & Safety Academy Ltd | Administrative & support | 2019 |
| Internet Business London Limited | Information & communication | 2021 |
| Interstock Ltd | Wholesale & retail | 2025 |
| Intra Private Finance 2 Limited | Financial services | 2019 |
| Intra Private Finance Ltd | Professional & scientific | 2018 |
| Invertone Limited | Professional & scientific | 2016 |
| Investash Limited | Construction | 2020 |
| Investment Wealth Ltd | Real estate | 2024 |
| Ioana Cares Ltd | Health & social care | 2025 |
| IP (LC) Limited | Professional & scientific | 2025 |
| IP Smart Mortgage Solutions Ltd | Financial services | 2025 |
| Iplan Ltd | Construction | 2023 |
| IQ Orthodontics Limited | Health & social care | 2010 |
| Iredan Ltd | Construction | 2025 |
| Iridium Corporation Limited | Information & communication | 2007 |
| Iris ( International Risk Intelligence System) Limited | Information & communication | 2025 |
| IRM Homes Ltd | Construction | 2020 |
| Irwin Consulting Engineers Ltd | Construction | 2022 |
| Isayit Ltd | Wholesale & retail | 2017 |
| Iskandi Ltd | Wholesale & retail | 2020 |
| Isla VER Limited | Administrative & support | 2020 |
| Islands on the Air (Iota) Ltd | Arts & recreation | 2016 |
| Isolee Ltd | Hospitality | 2023 |
| Ison Management Limited | Professional & scientific | 2013 |
| Ison Services Limited | Information & communication | 2025 |
| Ison Travel Limited | Administrative & support | 2006 |
| Isquare Trading Ltd | Wholesale & retail | 2020 |
| Issa Designs Ltd | Professional & scientific | 2024 |
| Issee Limited | Education | 2000 |
| Istanbul Turkish Haircut Ltd | Other services | 2022 |
| Istvan Transport Ltd | Transport & logistics | 2021 |
| Istylists Limited | Wholesale & retail | 2010 |
| IT Leadz Ltd | Wholesale & retail | 2024 |
| IT Repair Services Ltd | Information & communication | 2026 |
| IT Training & Consultancy Limited | Professional & scientific | 2001 |
| It's a Dog's Dinner Limited | Manufacturing | 2020 |
| IT24BY7 Limited | Information & communication | 2024 |
| ITA Properties Ltd | Real estate | 2004 |
| Italia Conti Arts Centre Limited | Education | 2001 |
| Italia Conti Virtual Limited | Education | 2024 |
| Italian Inspiration Limited | Other services | 2013 |
| Italo Bay Ltd | Wholesale & retail | 2025 |
| Italtaste Limited | Hospitality | 2010 |