| IAN Wilson Plant Training and Testing Ltd | Education | 2026 |
| IBC Property Limited | Real estate | 2023 |
| Ibiz Consulting Limited | Information & communication | 2017 |
| Ibizify.Net Ltd | Information & communication | 2012 |
| Icknield Archaeology Ltd | Professional & scientific | 2014 |
| ICL Proguard Ltd | Administrative & support | 2023 |
| Iconic Consulting Services Ltd | Professional & scientific | 2023 |
| Ideal UK Solutions Limited | Professional & scientific | 2016 |
| Idiris Limited | Administrative & support | 1998 |
| IDM Electrical Ltd | Construction | 2023 |
| IDS Motorsport Ltd | Professional & scientific | 2024 |
| IE Project Management Ltd | Professional & scientific | 2025 |
| Iemillar Ltd | Real estate | 2024 |
| Iengineer Solutions Limited | Information & communication | 2023 |
| IH Living Ltd | Real estate | 2025 |
| IHJ Management Limited | Professional & scientific | 2015 |
| IHJ Properties 1 Limited | Real estate | 2023 |
| IHJ Securities Ltd | Real estate | 2019 |
| Ihos Holdings Limited | Financial services | 2023 |
| Iintra Limited | Wholesale & retail | 2020 |
| IL Divino Doors & Windows Oxford Ltd | Construction | 2025 |
| Illumin-Nation Limited | Wholesale & retail | 2006 |
| Iluminessence Ltd | Arts & recreation | 2023 |
| Image First Solutions Limited | Wholesale & retail | 2008 |
| Imagex Bicester Limited | Wholesale & retail | 2017 |
| Imagine (Apartments) Management Company Limited | Households | 2014 |
| Imagine AI Group Ltd | Information & communication | 2026 |
| Imagine and Dream Limited | Administrative & support | 2008 |
| Imc&T Ltd | Professional & scientific | 2013 |
| Imets Europe Ltd | Wholesale & retail | 2012 |
| Immortal Training Ltd | Health & social care | 2018 |
| Imperial Media Ltd | Administrative & support | 2017 |
| IMS (1959) Consultancy Limited | Information & communication | 2019 |
| IMS Independent Mortgage Solutions Ltd | Financial services | 2008 |
| IMS Lettings Solutions Limited | Real estate | 2015 |
| IMS Property Group Limited | Administrative & support | 2015 |
| IMS Property Investment Limited | Real estate | 2018 |
| IMS Property Solutions Limited | Other services | 2015 |
| Indies Treasure Ltd | Wholesale & retail | 2024 |
| Induced Energy Limited | Manufacturing | 1992 |
| Infinite PIE Ltd | Education | 2007 |
| Infinite YOU Limited | Professional & scientific | 2007 |
| Infinity JIN Limited | Wholesale & retail | 2025 |
| Informatics Matters Limited | Information & communication | 2003 |
| Information AGE Resources Ltd | Information & communication | 2024 |
| Informed Leisure Limited | Extraterritorial | 2000 |
| Ingles Medical Limited | Health & social care | 2013 |
| Ingram Hill Limited | Professional & scientific | 2015 |
| Inkcho Designs Ltd | Professional & scientific | 2025 |
| Innerzone Ltd | Education | 2025 |
| Innovate Mulligan Investments Ltd | Real estate | 2023 |
| Innovation for Growth Limited | Professional & scientific | 2010 |
| Innside Property Ltd | Administrative & support | 2025 |
| Inprotech Limited | Information & communication | 2021 |
| Inrigo Ltd | Real estate | 2023 |
| Inside OUT Bathrooms Limited | Real estate | 1999 |
| Inside OUT Developments Limited | Construction | 1991 |
| Inside OUT Electrical Limited | Professional & scientific | 2001 |
| Inside OUT Estates Limited | Real estate | 2001 |
| Inside OUT Group Limited | Financial services | 2021 |
| Inside OUT Holdings Limited | Construction | 1999 |
| Inside OUT Kitchens Limited | Extraterritorial | 1996 |
| Inside OUT Paint Supplies Limited | Wholesale & retail | 2000 |
| Inside OUT Showrooms Limited | Manufacturing | 1993 |
| Inside OUT Tile Supplies Limited | Professional & scientific | 2001 |
| Insight (Oxford) Ltd | Professional & scientific | 1998 |
| Insight 2000 Limited | Professional & scientific | 1990 |
| Insightful Applications Limited | Administrative & support | 2015 |
| Insights AI Ltd | Real estate | 2025 |
| Inspired Living Oxfordshire Ltd | Real estate | 2022 |
| Integral Operations Ltd | Professional & scientific | 2023 |
| Intelligent Business Change Limited | Professional & scientific | 2021 |
| Intelligent MTD Limited | Professional & scientific | 2018 |
| Interalpha Financial Planning Limited | Financial services | 2017 |
| Interduct UK Limited | Administrative & support | 2005 |
| Interim Assistance Limited | Professional & scientific | 2002 |
| Interim GC Limited | Administrative & support | 2024 |
| Interior Project Services Limited | Administrative & support | 2002 |
| International Coaching & Development Limited | Professional & scientific | 2010 |
| International Motor Sports Limited | Professional & scientific | 1994 |
| International Travel & Business Investments Limited | Administrative & support | 1998 |
| Interplan Electrics Limited | Construction | 1997 |
| Intreqa Limited | Wholesale & retail | 2026 |
| Intrim Ltd | Wholesale & retail | 2019 |
| Investfront (Oxon) Limited | Construction | 2007 |
| Investment Properties Management Limited | Real estate | 2023 |
| Invictus Strategic Solutions Ltd | Professional & scientific | 2022 |
| Inway Scaffolding Ltd | Construction | 2021 |
| Ioas Investment Ltd | Real estate | 2021 |
| ION Packaging Ltd | Administrative & support | 2023 |
| IOT Wireless Ltd | Administrative & support | 2017 |
| Ioto Homes Ltd | Real estate | 2021 |
| Ireson-Bailey Construction Ltd | Construction | 2017 |
| Ireson-Bailey Ltd | Administrative & support | 2016 |
| IRL Enterprise Limited | Administrative & support | 2025 |
| Ishanvi Estates Ltd | Real estate | 2022 |
| Itemtracker Software Ltd. | Information & communication | 2009 |
| Itineris UN Limited | Administrative & support | 2023 |
| Itoxel Ltd | Information & communication | 2025 |
| ITS Quai Ltd | Professional & scientific | 2023 |