| Imperial Midlands Limited | Health & social care | 2006 |
| Imperial National Ltd | Extraterritorial | 2008 |
| Impiger Management Consultants Limited | Professional & scientific | 2024 |
| Impressive Events Limited | Administrative & support | 2012 |
| Imprimeo Ltd | Manufacturing | 2024 |
| IN One Consulting Ltd | Professional & scientific | 2012 |
| IN2TEC Limited | Manufacturing | 2000 |
| Inbox Securities Ltd | Transport & logistics | 2019 |
| Incharge(Uk) Limited | Wholesale & retail | 2020 |
| Incognito Systems Limited | Administrative & support | 2017 |
| Indaba Wealth Management Limited | Financial services | 2021 |
| Indedam Limited | Health & social care | 2021 |
| Independent Battery Group Ltd | Financial services | 2025 |
| Independent Rehabilitation Services Limited | Health & social care | 2007 |
| Indie Sales Ltd | Professional & scientific | 2023 |
| Indori Brothers Ltd | Hospitality | 2025 |
| Indrive Cars Ltd | Transport & logistics | 2026 |
| Inductronics Lamp Column Car Charging Ltd | Professional & scientific | 2014 |
| Inductronics Technology Research & Development Ltd | Professional & scientific | 2007 |
| Indulgence Beauty Limited | Other services | 2017 |
| Indulgence Hairdressing Limited | Other services | 2018 |
| Infinitas Accountants Limited | Professional & scientific | 2020 |
| Infinite Beginnings Limited | Administrative & support | 2024 |
| Infinite Electricity Limited | Professional & scientific | 2023 |
| Infinite Wealth Limited | Construction | 2026 |
| Infiniti Cars Ltd | Transport & logistics | 2026 |
| Infotel Consulting Limited | Information & communication | 2005 |
| Inframe Communications Limited | Professional & scientific | 2026 |
| Ingtrans Logistics Ltd | Transport & logistics | 2015 |
| Initiation Sounds Ltd | Arts & recreation | 2025 |
| Injection Moulding Supplies Limited | Professional & scientific | 2026 |
| Inkwazi Trading Company Limited | Professional & scientific | 2001 |
| Inland & Marine Services Ltd | Construction | 2013 |
| Innisfree Advisory Limited | Professional & scientific | 2025 |
| Innovating Assets Limited | Real estate | 2018 |
| Inovex Systems Limited | Manufacturing | 2000 |
| Inside EYE Ltd | Administrative & support | 2013 |
| Inside OUT Homeworks Limited | Construction | 2026 |
| Insidedata Ltd | Information & communication | 2011 |
| Insight Circle Ltd | Professional & scientific | 2026 |
| Insight Professional Partners Ltd | Professional & scientific | 2026 |
| Insights Ahead Limited | Education | 2018 |
| Insignia Global Group Ltd | Public administration | 2025 |
| Inspirations Kitchens & Bathrooms Ltd | Administrative & support | 2026 |
| Inspire 2B Active Midlands Limited | Arts & recreation | 2026 |
| Inspire ME Events Ltd | Administrative & support | 2018 |
| Intec Foams Limited | Manufacturing | 2024 |
| Integra Asset Finance Limited | Financial services | 2008 |
| Integral Contracts Limited | Construction | 2026 |
| Integrated Services (Northants) Ltd | Other services | 1976 |
| Integritas Learning Limited | Education | 2014 |
| Intelex Group (UK) Ltd | Wholesale & retail | 1995 |
| Intelex Group Holdings (UK) Limited | Financial services | 2021 |
| Intelli-Id Ltd | Information & communication | 2025 |
| Intelligent Firmware Limited | Extraterritorial | 1997 |
| Intelsol Ltd | Professional & scientific | 2019 |
| Interactive Care Solutions Ltd | Health & social care | 2024 |
| Interactive Fleet Management Limited | Administrative & support | 2010 |
| Interconnectsdata Limited | Information & communication | 2015 |
| Intercounty Vehicles Limited | Transport & logistics | 2017 |
| International Leather Products Limited | Wholesale & retail | 2004 |
| International Machine Associates Ltd | Professional & scientific | 2009 |
| International News Ltd | Information & communication | 2020 |
| International Rail Solutions Limited | Professional & scientific | 2024 |
| Interroll (Engineering) Limited | Professional & scientific | 1970 |
| Interroll Limited | Manufacturing | 1981 |
| Intertrade Maintenance Ltd | Other services | 2023 |
| Intib EX Services Ltd | Real estate | 2015 |
| Intogaia Ltd | Wholesale & retail | 2019 |
| Intra Agra Ltd | Professional & scientific | 2007 |
| Invivo Wines UK Ltd | Wholesale & retail | 2018 |
| IP (Harlow) Limited | Real estate | 2026 |
| Iper Film Limited | Professional & scientific | 2022 |
| IPM Catering Limited | Administrative & support | 2007 |
| IQ Cyber Solutions Ltd | Information & communication | 2023 |
| Iraqi Medical Association Uk&Eu Ltd | Health & social care | 2025 |
| Irispoint Strategy Limited | Information & communication | 2026 |
| Iron Life Property Limited | Real estate | 2025 |
| Irons Developments Ltd | Construction | 2024 |
| Ironside Holdings Limited | Financial services | 2004 |
| Ironstone Wellbeing Limited | Arts & recreation | 2019 |
| Irotech Motors Ltd | Transport & logistics | 2019 |
| IRX Limited | Information & communication | 2016 |
| IS Electrical Ltd | Administrative & support | 2017 |
| Isa-Online Limited | Financial services | 1998 |
| Isaac Holdings Ltd | Other services | 2019 |
| Isabella Shedrack Coaching and Consulting Ltd | Health & social care | 2024 |
| ISE Communications Limited | Information & communication | 2006 |
| ISE Lodge News Limited | Wholesale & retail | 2017 |
| ISE Lodge Takeaway Ltd | Hospitality | 2026 |
| ISE Property Investments Ltd | Real estate | 2021 |
| Isebrook Properties Limited | Real estate | 2022 |
| Isham Accounting Services Limited | Professional & scientific | 2020 |
| Isis Legal Ltd | Professional & scientific | 2007 |
| Islip Forestry Limited | Administrative & support | 2023 |
| Ismart Group Limited | Financial services | 2004 |
| Isotirys Ltd | Transport & logistics | 2021 |
| Istina Consulting Limited | Professional & scientific | 2026 |
| Istratex Logistic & Travel Ltd | Transport & logistics | 2019 |
| Itam Worx Limited | Information & communication | 2022 |