| Inspire Medical Solutions Limited | Professional & scientific | 2015 |
| Inspire Sales Management & Events Ltd | Hospitality | 2017 |
| Inspire Timber Frame Limited | Construction | 2012 |
| Inspired Clothing & Merchandise Ltd | Wholesale & retail | 2025 |
| Inspired Gaming Lounge Ltd | Arts & recreation | 2022 |
| Inspired Martial Arts Huntingdon Ltd | Arts & recreation | 2025 |
| Inspired Martial Arts Ltd | Arts & recreation | 2011 |
| Inspired Play Limited | Arts & recreation | 2022 |
| Inspired Play Town Ltd | Arts & recreation | 2022 |
| Inspired to Change Ltd | Other services | 2011 |
| Inspired Training and Development Ltd | Education | 2022 |
| Inspiring Solutions Group Limited | Manufacturing | 2016 |
| Insta IT Services UK Ltd | Information & communication | 2018 |
| Installed Limited | Manufacturing | 2014 |
| Instamessage Limited | Information & communication | 2020 |
| Instant Delivery Service Ltd | Transport & logistics | 2019 |
| Instant Engineering Ltd | Professional & scientific | 2024 |
| Institute of Scientific and Technical Communicators(The) | Other services | 1972 |
| Institutional Development and Management Consultants Limited | Professional & scientific | 2019 |
| Instytut of Nano Coatings and Composites Limited | Manufacturing | 2018 |
| Insure Solutions Ltd | Professional & scientific | 2018 |
| Insure Value Ltd | Financial services | 2023 |
| INSURE4SURE Ltd | Financial services | 2010 |
| Insurewise Limited | Financial services | 1993 |
| Insync Games Limited | Manufacturing | 2019 |
| Intacept Management Limited | Administrative & support | 1993 |
| Intacept Security Limited | Extraterritorial | 1991 |
| Integral 2 Limited | Professional & scientific | 2001 |
| Integrating Technologies Limited | Information & communication | 2008 |
| Integrity Education Specialists Ltd | Transport & logistics | 2025 |
| Integrity Engineering Solutions Limited | Professional & scientific | 2024 |
| Integrity Stays Ltd | Real estate | 2025 |
| Integrity Team Limited | Information & communication | 2018 |
| Integrity Workforce Ltd | Construction | 2026 |
| Integrityy Cars Ltd | Wholesale & retail | 2026 |
| Intelecom Limited | Professional & scientific | 1996 |
| Inter Cannary Properties Ltd | Real estate | 2022 |
| Inter Group (Cambs) Ltd | Wholesale & retail | 2026 |
| Inter Novum + UK LLP | | 2025 |
| Inter Novum Ltd | Wholesale & retail | 2025 |
| Inter Novum UK + Ltd | Wholesale & retail | 2026 |
| Interblock Paving Limited | Construction | 2016 |
| Intercarparts Ltd | Wholesale & retail | 2017 |
| Interceptor Security Limited | Administrative & support | 2025 |
| Intercity Nationwide Associates Ltd | Real estate | 2012 |
| Intercontinental Clothing Limited | Wholesale & retail | 2025 |
| Intercounty Limited | Extraterritorial | 1998 |
| Interfer Steel Limited | Wholesale & retail | 2008 |
| Interhire Power Tool Services Limited | Wholesale & retail | 1983 |
| Interior & Exterior Construction Ltd | Construction | 2023 |
| Interiors by MT Design Limited | Professional & scientific | 2019 |
| Interlink Care Services Limited | Health & social care | 2022 |
| Interlink Express Ltd | Transport & logistics | 2026 |
| International Asset Reclaim Ltd | Wholesale & retail | 2025 |
| International Federation for Produce Standards | Other services | 2006 |
| International Food Centre Peterborough Ltd | Wholesale & retail | 2022 |
| International Foods (Boston) Ltd | Wholesale & retail | 2019 |
| International Recycling Industries Limited | Professional & scientific | 1995 |
| International Safety Culture Limited | Professional & scientific | 2026 |
| International School of Nutritional Medicine Ltd | Education | 2025 |
| International Store Limited | Wholesale & retail | 2018 |
| International Store M Ltd | Wholesale & retail | 2026 |
| International Veterinary Solutions Ltd | Professional & scientific | 2022 |
| Internet Empire Ltd | Wholesale & retail | 2015 |
| Internet Sciences Limited | Information & communication | 1997 |
| Internwise Limited | Professional & scientific | 2023 |
| Interovations Group Holding Ltd | Financial services | 2025 |
| Interovations Ltd | Construction | 2025 |
| Intotek Ltd | Information & communication | 2025 |
| Intra-Grated Limited | Wholesale & retail | 2024 |
| Intraquad Ltd | Professional & scientific | 2019 |
| Intrinsic Security (UK) Limited | Information & communication | 2025 |
| Intuitive Standard Limited | Real estate | 2015 |
| Intzom Ltd | Wholesale & retail | 2025 |
| Inventcheck Ltd | Real estate | 2020 |
| Investco Capital Holdings Ltd | Real estate | 2025 |
| Investedd Ltd | Professional & scientific | 2024 |
| Investment Property LAB Ltd | Wholesale & retail | 2020 |
| Investments & Moore Limited | Financial services | 2024 |
| Invicta Recruitment Limited | Administrative & support | 2019 |
| Invictus Virtus Ltd | Financial services | 2025 |
| Ionica Holdings Limited | Real estate | 2018 |
| Ionica Trading Limited | Professional & scientific | 2019 |
| Ionid Ltd | Professional & scientific | 2025 |
| Ionut Badin Limited | Transport & logistics | 2014 |
| Ionut Hercule Ltd | Transport & logistics | 2018 |
| Ionviorel Limited | Transport & logistics | 2017 |
| Iosys Consultancy Ltd. | Information & communication | 2021 |
| Iotica Limited | Information & communication | 2018 |
| Ip&G Ltd | Professional & scientific | 2023 |
| IPC Associates Limited | Professional & scientific | 2017 |
| IPH Engineering Ltd | Professional & scientific | 2015 |
| Ipiphany AI UK Limited | Information & communication | 2019 |
| Iproactive Products Ltd | Wholesale & retail | 2020 |
| Ipsnare Limited | Information & communication | 2026 |
| Ipuk-(Integration Party UK) Ltd | Hospitality | 2022 |
| IQ Berries Services Limited | Administrative & support | 2022 |
| IQ Cleaning Services Ltd | Administrative & support | 2026 |
| IQ Shelter CIC | Real estate | 2022 |
| IQ88 Entreprises Limited | Wholesale & retail | 2005 |