| House of ABI Ltd | Other services | 2023 |
| House of Chadwick Ltd | Arts & recreation | 2025 |
| House of Dalrymple Ltd | Administrative & support | 2025 |
| House of Peggy Ltd | Real estate | 2025 |
| House of Yaqub Properties Ltd | Real estate | 2024 |
| House Party Flowers Ltd | Wholesale & retail | 2020 |
| Household Readiness Limited | Information & communication | 2026 |
| Houston Investments Limited | Real estate | 1997 |
| HOW to Heal Limited | Health & social care | 2023 |
| Howse and O'Reilly (Witney) Limited | Construction | 1976 |
| HPC GAS Ltd | Other services | 2019 |
| HSW (Milton Keynes) Limited | Wholesale & retail | 2014 |
| HTU Life Ltd | Manufacturing | 2021 |
| Hughes Films Limited | Arts & recreation | 2023 |
| Humanitarian Data Solutions Limited | Professional & scientific | 2018 |
| Humberstone-Garley Limited | Extraterritorial | 2006 |
| Humble Priory Limited | Information & communication | 2022 |
| Hunker Down Limited | Real estate | 2020 |
| Hunters Farm Ltd | Agriculture & fishing | 2022 |
| Huxley Consulting Ltd | Information & communication | 2024 |
| Hyatt Enterprises Limited | Financial services | 2025 |
| Hydes Pipes Ltd | Wholesale & retail | 2020 |
| Hydro JET Washing Ltd | Administrative & support | 2019 |
| Hyperformance Supplements Ltd | Wholesale & retail | 2025 |
| I & H Plastering Limited | Construction | 2015 |
| I&T Witney Ltd | Hospitality | 2022 |
| I. D. Godden & Co Limited | Construction | 2004 |
| I2 Security Limited | Administrative & support | 2006 |
| I2 Technology Holdings Limited | Financial services | 2022 |
| IAA Investment Limited | Real estate | 2019 |
| IAN Mclennan Ltd | Extraterritorial | 2024 |
| IAN Nolan Events Ltd | Other services | 2011 |
| Ibis Innovation Limited | Professional & scientific | 2023 |
| IC Windows Doors & Conservatories Ltd | Construction | 2026 |
| Icad Solutions Ltd | Extraterritorial | 2015 |
| Ice Hairdressing Oxford Ltd | Other services | 2013 |
| Iceoxford Limited | Manufacturing | 2004 |
| Icomply Solutions Ltd | Professional & scientific | 2024 |
| Icrack Witney Ltd | Wholesale & retail | 2024 |
| Icsss Limited | Manufacturing | 2015 |
| ID Developments (UK) Limited | Real estate | 2013 |
| Idlewild Hairdressing Ltd | Other services | 2009 |
| Idyoo U.K. Limited | Information & communication | 2016 |
| IFA Consultancy Services Limited | Professional & scientific | 2025 |
| Ifaa Capital Ltd | Financial services | 2026 |
| Ifaa Group Limited | Real estate | 2022 |
| IFS Property Investment Ltd | Real estate | 2018 |
| Iglory Limited | Professional & scientific | 2008 |
| Iizzat Capital Ltd | Financial services | 2026 |
| Immedio Ltd | Information & communication | 2011 |
| Impact Pumps Limited | Manufacturing | 2020 |
| Impact.Ai Limited | Information & communication | 2017 |
| Imperial Holiday Rentals Ltd | Real estate | 2017 |
| Imperial Meat Co. Limited | Manufacturing | 1969 |
| Impulse Energy Solutions (Wellingborough) Limited | Energy | 2017 |
| Impulse Energy Solutions Limited | Energy | 2013 |
| IN Friendship Ltd | Health & social care | 2023 |
| Incentives Events and Meetings Ltd. | Administrative & support | 2013 |
| Income Tax Ltd | Information & communication | 2018 |
| Incorporation Works Ltd | Professional & scientific | 2014 |
| Indigo Fade Production Ltd | Information & communication | 2014 |
| Indigo Wellness Ltd | Health & social care | 2025 |
| Inferential Limited | Information & communication | 2023 |
| Infinito Consulting Limited | Information & communication | 2019 |
| Infinity Landscapes and Design Ltd | Administrative & support | 2023 |
| Infrastruct CS (Oxford) Limited | Professional & scientific | 2020 |
| Infrastruct CS Limited | Professional & scientific | 2011 |
| Ingersoll Engineers UK LLP | | 2013 |
| Inhaling Infinity Ltd | Health & social care | 2024 |
| Inks & More Limited | Wholesale & retail | 2006 |
| Inktec Europe Limited | Wholesale & retail | 2003 |
| Inner Vision Therapies Ltd | Administrative & support | 2025 |
| Innovate NP Ltd | Information & communication | 2022 |
| Innovatinghr Ltd | Professional & scientific | 2014 |
| Innovox Limited | Information & communication | 2024 |
| Insight Appointments Limited | Administrative & support | 2003 |
| Insight Care Ltd | Health & social care | 2020 |
| Insight MW Limited | Professional & scientific | 2017 |
| Insight Planning & Design Ltd | Construction | 2025 |
| Insight PMI Ltd | Real estate | 2018 |
| Insight to Design Ltd | Wholesale & retail | 2021 |
| Insights Into Business Limited | Information & communication | 2016 |
| Insink UK Group Limited | Construction | 2025 |
| Insink UK Ltd | Construction | 2024 |
| Inspire Medilaw Experts Limited | Other services | 2024 |
| Inspire Medilaw Limited | Education | 2022 |
| Inspire Studio Oxford Ltd | Education | 2024 |
| INSPIRE2 Ltd | Education | 2025 |
| Inspired Construction Oxford Limited | Construction | 2014 |
| Inspired Health Outcomes Limited | Professional & scientific | 2022 |
| Inspiromics Limited | Professional & scientific | 2019 |
| Install Oxford Limited | Construction | 2023 |
| Instawow Ltd | Professional & scientific | 2020 |
| INTEGR8UK Ltd | Professional & scientific | 2024 |
| Integrec Limited | Administrative & support | 2017 |
| Integrity Investigations Ltd | Administrative & support | 2015 |
| Inter Pares Limited | Administrative & support | 2018 |
| Interlinguae Ltd | Professional & scientific | 2009 |
| Intermode Research Ltd | Professional & scientific | 2021 |
| International Humanist Publications Ltd | Information & communication | 2018 |