| Innovspace Ltd | Information & communication | 2024 |
| Inocat Solutions Ltd | Professional & scientific | 2025 |
| Inreporting Ltd | Health & social care | 2023 |
| Inresin Limited | Information & communication | 2021 |
| Inrev Limited | Professional & scientific | 2025 |
| Insignia Hotels Limited | Professional & scientific | 2018 |
| Inspire Chiropractic Limited | Health & social care | 2008 |
| Inspire Education (UK) Limited | Education | 2013 |
| Inspire Events Ltd | Other services | 2020 |
| Inspire Executive Solutions Limited | Professional & scientific | 2005 |
| Inspire Oxford Summer School Ltd | Education | 2024 |
| Inspired Creation Limited | Real estate | 2010 |
| Inspired Luxury Life Ltd | Wholesale & retail | 2021 |
| Inspired Restorations Oxford Limited | Construction | 2013 |
| Inspired Transformation Consultancy Ltd | Information & communication | 2020 |
| Inspires Community Provision CIC | Education | 2026 |
| Inspires Tuition Ltd | Education | 2025 |
| Inspiring Action Ltd | Professional & scientific | 2014 |
| Inspiware Limited | Information & communication | 2018 |
| Instance Ltd | Information & communication | 2026 |
| Instil Design Limited | Other services | 2012 |
| Instill Education Limited | Education | 1977 |
| Institute for Food, Brain and Behaviour | Professional & scientific | 1984 |
| Institute for Health Economics and Outcomes Research Limited | Education | 2014 |
| Institute of Animal Technology(The) | Education | 1965 |
| Instruct Ltd | Professional & scientific | 2014 |
| Instrumentel Limited | Manufacturing | 2001 |
| Insure Africa Ltd | Information & communication | 2026 |
| Integrate Community CIC | Education | 2026 |
| Integrated Assessors Ltd | Health & social care | 2026 |
| Integrated Limited | Administrative & support | 2016 |
| Integritec (UK) Limited | Information & communication | 2008 |
| Integro Solutions Ltd | Health & social care | 2010 |
| Intelactsoft UK Ltd | Information & communication | 2017 |
| Intellekt Limited | Administrative & support | 2002 |
| Intelligene Diagnostics Ltd | Professional & scientific | 2025 |
| Intelligent Connections Limited | Administrative & support | 2019 |
| Inter G Construction Limited | Manufacturing | 2022 |
| Inter Proposal Services Ltd | Administrative & support | 2014 |
| INTER.NATIONAL69 Ltd | Manufacturing | 2025 |
| Interactive Pharma Solutions Limited | Professional & scientific | 2014 |
| Interface Publications Limited | Manufacturing | 2006 |
| Interference Works Limited | Professional & scientific | 2025 |
| Interior Ease Construction Ltd | Construction | 2024 |
| Interior Spectrum Limited | Other services | 2007 |
| Interlink (UK) Ltd. | Professional & scientific | 2013 |
| International Active Group Limited | Financial services | 2022 |
| International Association of Animal Therapists Limited | Other services | 2021 |
| International Certificate of Christian Education Limited | Education | 2009 |
| International Conference Network Limited | Professional & scientific | 1989 |
| International Fellowship of Evangelical Students | Other services | 1966 |
| International Innovation Services (Internacia Novigo Servoj) Ltd | Professional & scientific | 2016 |
| International Network for Advancing Science and Policy Ltd | Professional & scientific | 2003 |
| International Non-Governmental Organisation Training and Research Centre ("Intrac") | Professional & scientific | 1991 |
| International Pole and Line Foundation | Health & social care | 2011 |
| International Proposals Academy Ltd | Administrative & support | 2011 |
| International Roofing Ltd | Construction | 2026 |
| International Tree Foundation | Other services | 2004 |
| Internet Tickets Limited | Information & communication | 2002 |
| Intersection M&A Ltd. | Professional & scientific | 2016 |
| Intrepid ANT Limited | Information & communication | 2013 |
| Intrepid Consulting Engineers Limited | Professional & scientific | 2010 |
| Intrinity Food and Beverage Limited | Wholesale & retail | 2021 |
| Intxco Ltd | Wholesale & retail | 2024 |
| INVEST2RE.COM Ltd | Financial services | 2021 |
| Investec Group (UK) Limited | Professional & scientific | 1988 |
| Investment Product Research Limited | Information & communication | 2013 |
| Investment-Hands on Business Solutions Limited | Other services | 2016 |
| Investocity Ltd | Financial services | 2021 |
| Inviscid Ltd | Professional & scientific | 2019 |
| Invisible East 2036 C.I.C. | Professional & scientific | 2026 |
| Invivusbio Limited | Professional & scientific | 2012 |
| Invoke Technology Limited | Information & communication | 2002 |
| Inyo Energy Ltd | Construction | 2018 |
| Iolabs-Uk Limited | Professional & scientific | 2021 |
| Ionsight Analytics Ltd | Professional & scientific | 2024 |
| IP Asset Group Limited | Financial services | 2024 |
| IP Elements Ltd | Manufacturing | 2020 |
| IPM Oxford Ltd | Construction | 2024 |
| IQ Homecare Ltd | Health & social care | 2018 |
| IQ Properties Management Ltd | Households | 2020 |
| Iquira Energy Innovation Limited | Professional & scientific | 2021 |
| Iranian Community Network Ltd | Health & social care | 2022 |
| Iraqi Women Art and WAR CIC | Administrative & support | 2024 |
| IRE Cleaning Services Limited | Administrative & support | 2025 |
| Irene Holidays Ltd | Administrative & support | 2022 |
| Iris Ideas Ltd | Professional & scientific | 2025 |
| IRL Press Limited | Information & communication | 1974 |
| IRL Ventures Ltd | Arts & recreation | 2025 |
| Iron Cars Ltd | Transport & logistics | 2026 |
| Iron Works Investments Limited | Construction | 2005 |
| Ironclad AI Limited | Information & communication | 2025 |
| Irongate Systems Ltd Limited | Information & communication | 2025 |
| Irrelevant Ltd | Wholesale & retail | 2026 |
| Iruvis Limited | Professional & scientific | 2004 |
| Irving Gallery Limited | Wholesale & retail | 2023 |
| Isabella Millay Limited | Other services | 2006 |
| Isgw Property Limited | Real estate | 2025 |
| Isis Audio Visuals Limited | Information & communication | 2008 |
| Isis Financial Planners Limited | Financial services | 2001 |