| ILR Investments Ltd | Financial services | 2025 |
| Imali Accounting Ltd | Professional & scientific | 2023 |
| Imali Travel Ltd | Administrative & support | 2023 |
| Imani Living Limited | Administrative & support | 2024 |
| Immaculate Conception Printing Ltd | Manufacturing | 2002 |
| Imobert Ltd | Professional & scientific | 2018 |
| Impact Boxing Ltd | Education | 2023 |
| Impact Nation Ltd | Information & communication | 2026 |
| Impaka Limited | Real estate | 2017 |
| Imperial Foods Holdings Limited | Professional & scientific | 1926 |
| Imperial Group Limited | Professional & scientific | 1952 |
| Imperial Seafoods Limited | Professional & scientific | 1929 |
| Imperial Trades Ltd | Construction | 2020 |
| Impetus Management Company Ltd | Households | 2004 |
| Improve Your World Publishers Co Limited | Information & communication | 2018 |
| Impulselogic Limited | Information & communication | 2008 |
| IN Demand Limited | Extraterritorial | 2000 |
| IN the RAY Residents (Maidenhead) Limited | Households | 1978 |
| In-Store Pharmacy Limited | | 1985 |
| Inaadam IT Solution Ltd | Other services | 2023 |
| Inbound Digital Marketing Ltd | Administrative & support | 2009 |
| Incell Build & Design Ltd | Information & communication | 2020 |
| Inceo Group Limited | Professional & scientific | 2025 |
| Include-Ed Limited | Education | 2016 |
| Independent Insight Social Solutions Ltd | Health & social care | 2023 |
| Independent Social Work Expert Assessments Ltd | Health & social care | 2020 |
| Inderpal Bhogal Architects Limited | Construction | 2017 |
| Indgo Ltd | Information & communication | 2018 |
| Indigo Gymnastics Club Limited | Arts & recreation | 2025 |
| Indika Group Ltd | Wholesale & retail | 2023 |
| Indira Logistics Ltd | Transport & logistics | 2024 |
| Indoor Urban Ltd | Administrative & support | 2026 |
| Industrial Electrical Networks Ltd | Information & communication | 2005 |
| Industrial Handling Solutions Limited | Manufacturing | 2004 |
| Industrium Group Limited | Information & communication | 2020 |
| Inex Contractors Ltd | Construction | 2017 |
| Infinite Cycle Ltd | Professional & scientific | 2024 |
| Infinite Soup Limited | Information & communication | 2025 |
| Infinitude Properties Limited | Real estate | 2020 |
| Infinity Cleaning Solutions Ltd | Administrative & support | 2024 |
| Infinity Electrical Innovations Limited | Construction | 2021 |
| Infinity Enterprise Group Limited | Financial services | 2022 |
| Infinity Homes (Berks) Limited | Real estate | 2018 |
| Infinity Ingredients Limited | Wholesale & retail | 2012 |
| Infinity Material Handling Limited | Wholesale & retail | 2026 |
| Infko Ltd | Information & communication | 2013 |
| Influxe Limited | Information & communication | 2013 |
| Information Systems Ltd | Information & communication | 2019 |
| Informed Independent Financial Advisers Ltd | Financial services | 2011 |
| Infosys Data Limited | Real estate | 2007 |
| INFOTECH9 Ltd | Information & communication | 2015 |
| Ingeni Solutions Limited | Professional & scientific | 2015 |
| Ingnity Ltd | Information & communication | 2022 |
| Ingwe Management Services Ltd | Information & communication | 1999 |
| Inkjunkie Ltd | Health & social care | 2018 |
| Innercircle Monster Limited | Financial services | 2021 |
| Innotatio Limited | Information & communication | 2012 |
| Innovarium Ltd | Professional & scientific | 2023 |
| Innovation Projects Ltd | Information & communication | 2011 |
| Innovative Events Ltd | Professional & scientific | 2021 |
| Innowise Consulting Limited | Professional & scientific | 2026 |
| Innside Ltd | Information & communication | 2017 |
| Innzak Limited | Manufacturing | 2026 |
| Inproit Ltd | Information & communication | 2019 |
| Insaneye Ltd | Information & communication | 2012 |
| Insight Buildings Ltd | Real estate | 2023 |
| Insight Certification Limited | Administrative & support | 1990 |
| Insight Professionals Limited | Professional & scientific | 2024 |
| Insightful Financial Solutions Limited | Professional & scientific | 2024 |
| Insource Marketing Limited | Information & communication | 1999 |
| Inspect Data Systems Limited | Information & communication | 2013 |
| Inspirations (Maidenhead) Limited | Wholesale & retail | 2013 |
| Inspire Cricket Coaching Limited | Education | 2025 |
| Inspired Sash Limited | Manufacturing | 2025 |
| Int(X) Ltd | Information & communication | 2018 |
| Intake Experts Ltd | Information & communication | 2026 |
| Integrated Wireless Solutions Ltd | Information & communication | 2014 |
| Integratesoft Ltd | Information & communication | 2023 |
| Integrity HSE Ltd | Construction | 2026 |
| Intekk Ltd | Wholesale & retail | 2024 |
| Inteligate Ltd | Information & communication | 2012 |
| Intelligent Data Collection Limited | Professional & scientific | 2007 |
| Intelligent Land and Property Limited | Real estate | 2016 |
| Intellium Partners Limited | Professional & scientific | 2026 |
| Intelogica Limited | Information & communication | 2002 |
| Interesting Services Limited | Wholesale & retail | 2022 |
| Internal Consulting Group UK Limited | Professional & scientific | 2014 |
| International Air & Shipping Association Limited | Other services | 1997 |
| International Financial Publishing Limited | Information & communication | 2004 |
| Interstage Limited | Arts & recreation | 2024 |
| Intersystem Limited | Wholesale & retail | 1985 |
| Intuita Limited | Information & communication | 2013 |
| Invamed Health Limited | Extraterritorial | 2020 |
| Inventories Inc (Buckinghamshire) Limited | Administrative & support | 2010 |
| Investous Ltd | Financial services | 2020 |
| Invictus ARC Ltd | Professional & scientific | 2022 |
| Invitation Only Escapes Limited | Administrative & support | 2025 |
| Ionactive Consulting Limited | Professional & scientific | 2005 |
| IOT Insights Limited | Information & communication | 2014 |
| Iotlvl Ltd | Arts & recreation | 2020 |