| Inspiring Through Arts CIC | Information & communication | 2025 |
| Install Electrical Limited | Extraterritorial | 2012 |
| Install Mechanical Limited | Extraterritorial | 2015 |
| Install Plumbing and Heating Limited | Extraterritorial | 2014 |
| Install Plumbing Limited | Extraterritorial | 2014 |
| Install Projects Limited | Construction | 2011 |
| Installation Contract Engineers Limited | Energy | 1998 |
| Instar Coaching C.I.C. | Education | 2017 |
| Instarred Limited | Transport & logistics | 2023 |
| Instone Ventures Ltd | Professional & scientific | 2023 |
| Instore Solutions Ltd | Construction | 2010 |
| Instructor Portal Limited | Administrative & support | 2022 |
| Instruments and Laboratory Supplies Limited | Other services | 2017 |
| Insula Vecta Limited | Financial services | 2025 |
| Insync Support Services Ltd | Administrative & support | 2021 |
| Intai Limited | Information & communication | 2025 |
| Intandem Systems Limited | Construction | 1997 |
| INTEGR8 Dance Limited | Arts & recreation | 2011 |
| INTEGR8 Franchise Limited | Arts & recreation | 2018 |
| Integra Tax Limited | Professional & scientific | 2008 |
| Integral Building Solutions South Ltd | Construction | 2024 |
| Integral Hire Limited | Administrative & support | 1988 |
| Integral Structures Limited | Construction | 1988 |
| Integrate Resources Limited | Professional & scientific | 2022 |
| Integrate Security Limited | Administrative & support | 2024 |
| Integrated Dynamic Analysis Limited | Construction | 2008 |
| Integritas Financial Advisers Limited | Financial services | 2015 |
| Integrity Data Limited | Information & communication | 2017 |
| Integrity Finance Limited | Financial services | 2003 |
| Integrity Indesign Ltd. | Professional & scientific | 1999 |
| Integrity Universal Products Ltd | Other services | 2019 |
| Inteliports Limited | Manufacturing | 2021 |
| Intelletech Limited | Information & communication | 2005 |
| Intelliforge Digital Ltd | Wholesale & retail | 2026 |
| Intelligent British Cooperation Ltd | Real estate | 2020 |
| Intelligent Instruments Ltd | Wholesale & retail | 2019 |
| Intelligent Refresh Ltd | Information & communication | 2025 |
| Intelligent Support Limited | Information & communication | 1999 |
| Intellugo Group Limited | Professional & scientific | 2026 |
| Intensale Limited | Wholesale & retail | 2019 |
| Interact UK Limited | Health & social care | 2007 |
| Interactive Code Ltd | Information & communication | 2019 |
| Intercept Ltd | Manufacturing | 2023 |
| Intercontinental Wines Limited | Wholesale & retail | 2011 |
| Interfruit Limited | Professional & scientific | 1963 |
| Intergalactic Party Co Limited | Arts & recreation | 2023 |
| Interglobal Electrics Limited | Wholesale & retail | 2015 |
| Interglobal Trade Group Ltd | Wholesale & retail | 2019 |
| Intergrain Limited | Professional & scientific | 2005 |
| Interior Construction & Installations Limited | Construction | 2006 |
| Interior Craft Studio Ltd | Education | 2025 |
| Interior Estates Limited | Construction | 2021 |
| Interiyours Ltd | Professional & scientific | 2022 |
| Interlock Locksmiths Ltd | Administrative & support | 2013 |
| Intermarine Enterprises Limited | Construction | 2013 |
| Intermarine GB Limited | Extraterritorial | 1996 |
| Intermarine Limited | Construction | 1996 |
| Internal Audit Forum Ltd | Other services | 2022 |
| International Association for Safety and Survival Training | Professional & scientific | 2010 |
| International Association of Maritime Institutions | Education | 2013 |
| International Barbers Ltd | Other services | 2022 |
| International Ecommerce Accountants Ltd | Professional & scientific | 2024 |
| International Food & Halal Meat Centre Limited | Wholesale & retail | 1999 |
| International Growth Partners Limited | Professional & scientific | 2022 |
| International Manufacturers Direct Sales Limited | Professional & scientific | 2001 |
| International Maritime Protection Group Limited | Administrative & support | 2017 |
| International NDT Ltd | Manufacturing | 2019 |
| Internetish Ltd | Information & communication | 2023 |
| Interpet Limited | Manufacturing | 2004 |
| Interphone Limited | Administrative & support | 1961 |
| Interrupt Media Ltd | Extraterritorial | 2023 |
| Interstellar Music Services Ltd | Arts & recreation | 2021 |
| Interstyle Bedrooms and Fitted Furniture Ltd | Manufacturing | 2020 |
| Intertouch UK Limited | Wholesale & retail | 2019 |
| Intertransservice Ltd | Wholesale & retail | 2020 |
| Interway Solutions Ltd | Information & communication | 2024 |
| Intext Solutions Ltd | Construction | 2024 |
| Intl Consult & Goods Trade Ltd | Administrative & support | 2008 |
| Into the Blue Charters Limited | Hospitality | 2026 |
| Into the PAN Limited | Extraterritorial | 2022 |
| Intrepid Turtle Limited | Information & communication | 2017 |
| Intu Floors Ltd | Construction | 2019 |
| Inven One Ltd | Administrative & support | 2026 |
| Inventiv Limited | Information & communication | 2023 |
| Inventive Air Corporate Limited | Extraterritorial | 2009 |
| Inveritas Property Inventories Limited | Administrative & support | 2014 |
| Inverness Moving & Storage Limited | Professional & scientific | 2011 |
| Invest Property Ltd | Real estate | 2019 |
| Investigative Solutions Ltd | Administrative & support | 2023 |
| Investments S.N.A Limited | Real estate | 2022 |
| Invicta London Jewellery Limited | Wholesale & retail | 2023 |
| Invictus Complex Care Ltd | Public administration | 2020 |
| Invictus Investment Corp LLP | | 2020 |
| Invictus Marine Ltd | Manufacturing | 2017 |
| Invincium Limited | Real estate | 2007 |
| Invisible Group Limited | Construction | 2019 |
| Invisifold Limited | Manufacturing | 2014 |
| Involve & Evolve Limited | Professional & scientific | 2013 |
| Iona Trans Limited | Transport & logistics | 2023 |
| Ionut&Lorena Limited | Construction | 2025 |