| Nexgen Football Academy Ltd | Education | 2025 |
| Next Step Dental Limited | Health & social care | 2026 |
| NH Digital Ltd | Information & communication | 2018 |
| NH Partnerships Ltd | Financial services | 2023 |
| Nice Tree Films Ltd | Information & communication | 2014 |
| Nicholas Dominic Osipczak Limited | Extraterritorial | 2025 |
| Nick Fathers Ltd | Professional & scientific | 2021 |
| Nick Scholfield Racing Limited | Arts & recreation | 2011 |
| Nicola Riley Consulting Ltd | Professional & scientific | 2024 |
| Nida Developments Limited | Real estate | 2020 |
| NIK Garden Limited | Administrative & support | 2022 |
| Nikki's Commercial Cleaning Services Ltd | Administrative & support | 2022 |
| Nina Raine Ltd | Arts & recreation | 2018 |
| NN Photos Ltd | Professional & scientific | 2020 |
| Nntechnn Ltd. | Financial services | 1999 |
| Noah Brothers Ltd | Wholesale & retail | 2019 |
| Noel Fehily Racing Limited | Arts & recreation | 2004 |
| Noel Fehily Racing Syndicates Limited | Arts & recreation | 2019 |
| Noisegate Limited | Arts & recreation | 2016 |
| NOPE23 Limited | Arts & recreation | 2019 |
| North East Distillery Co Ltd | Manufacturing | 2020 |
| Northampton IC Limited | Education | 2014 |
| Northbridge Ortho Limited | Health & social care | 2017 |
| Northcourt Residents Association Limited | Households | 1982 |
| Northeast Retreats Limited | Real estate | 2023 |
| Northquay Residents Association Limited | Households | 1996 |
| Northstar Keep Ltd | Information & communication | 2026 |
| Notora MED Ltd | Information & communication | 2026 |
| Noughts and Nibbles Limited | Hospitality | 2025 |
| Nova Air Services Limited | Transport & logistics | 2022 |
| Nova Bionics Ltd | Professional & scientific | 2026 |
| Nova Hair Studios Ltd | Other services | 2023 |
| Novaquest Computing Limited | Information & communication | 2015 |
| Nowhere Talent Limited | Arts & recreation | 2019 |
| NR Works Ltd | Other services | 2026 |
| NRG Live Limited | Arts & recreation | 2024 |
| NS Global Sports Limited | Financial services | 2026 |
| NSC Properties (Oxford) Ltd | Real estate | 2025 |
| Nuclear Matters Limited | Information & communication | 2015 |
| Nucleos Consulting Limited | Information & communication | 2022 |
| Numerical Edge Limited | Professional & scientific | 2014 |
| Nutrilab Pro Ltd | Professional & scientific | 2023 |
| Nuvelis Digital Ltd | Professional & scientific | 2025 |
| O'Leary Caravans Limited | Wholesale & retail | 2014 |
| OAC Holdings Limited | Financial services | 2019 |
| Oakfield Homes Limited | Construction | 2023 |
| Oakhurst Cleaning Limited | Administrative & support | 2023 |
| Oakley Park Management Limited | Households | 1971 |
| OAP Limited | Professional & scientific | 2018 |
| Oasis Oxford Ltd | Wholesale & retail | 2021 |
| Obvion Global Ltd | Transport & logistics | 2025 |
| OC Fitness Ltd | Arts & recreation | 2010 |
| Ocaid Wellbeing Limited | Information & communication | 1998 |
| OCK Environmental Limited | Extraterritorial | 2024 |
| OCK Hire (Abingdon) Limited | Transport & logistics | 1998 |
| OCK Hire Limited | Transport & logistics | 1976 |
| OCK House Management Limited | Households | 1986 |
| OCK Street Limited | Health & social care | 2008 |
| Octopus Publishing CIC | Information & communication | 2019 |
| Ocwaas Limited | Water & waste | 2025 |
| Ocwen 2016 Limited | Administrative & support | 2016 |
| Oddie's Pension Limited | Extraterritorial | 2015 |
| OG Hosting Ltd | Wholesale & retail | 2025 |
| OGI Tech Ltd | Wholesale & retail | 2025 |
| OHB Properties 2 Limited | Real estate | 2021 |
| OHB Properties Limited | Real estate | 2016 |
| OHB PROPERTIES3 Limited | Real estate | 2021 |
| OHS Supplies Limited | Wholesale & retail | 2018 |
| Oishi Abingdon Ltd | Hospitality | 2026 |
| Oishi Oxford Limited | Hospitality | 2024 |
| Oisin Murphy Racing Limited | Arts & recreation | 2015 |
| OKA Direct Limited | Wholesale & retail | 1999 |
| Okan Engineering Ltd | Professional & scientific | 2021 |
| Old Black Dog Holdings Limited | Financial services | 2018 |
| Old Station Yard Management Limited | Households | 2012 |
| Olenian Ltd | Professional & scientific | 2015 |
| Olex Films UK Ltd | Wholesale & retail | 2025 |
| Olof Consulting Ltd | Financial services | 2022 |
| Omfic Limited | Administrative & support | 2019 |
| ON Point Technical Ltd | Construction | 2024 |
| ON the Ground Coffee Ltd | Wholesale & retail | 2025 |
| ON the Sixth Day of January Ltd | Other services | 2015 |
| One Love Jamaican Street Food Ltd | Hospitality | 2023 |
| One Motion Limited | Administrative & support | 2011 |
| One Must Have Limited | Wholesale & retail | 2023 |
| One Planet Abingdon CEC Ltd | Information & communication | 2021 |
| Online Legal Services Limited | Professional & scientific | 2000 |
| Onlinevision Education Limited | Information & communication | 2020 |
| Only US Nobody Else Limited | Arts & recreation | 2020 |
| Oop.Me Limited | Professional & scientific | 2019 |
| Opcare Limited | Health & social care | 1994 |
| Open Questions Ltd | Information & communication | 2026 |
| Opiote Ltd | Financial services | 2025 |
| Optelma Lighting (UK) Limited | Construction | 1987 |
| Oracle Pool and Snooker Limited | Arts & recreation | 2015 |
| Orange Sparrow Limited | Transport & logistics | 2022 |
| Orano Limited | Professional & scientific | 1977 |
| Orbital RIG Systems Limited | Professional & scientific | 2025 |
| ORCESTR8 Ltd | Information & communication | 2026 |
| Orchard Construction Oxford Ltd | Construction | 2017 |