| Natura Cocktails Limited | Wholesale & retail | 2025 |
| Natural Landscapes Holdings Ltd | Extraterritorial | 2010 |
| Natural Landscapes Limited | Other services | 1990 |
| Navigate Audio Visual Limited | Administrative & support | 2026 |
| Navigate Success Ltd | Education | 2024 |
| Nayles Barn Quarry Limited | Mining & quarrying | 2021 |
| Neon Nation Limited | Information & communication | 2024 |
| Neptune Environmental Limited | Professional & scientific | 1999 |
| Neptune Oceanographics Limited | Professional & scientific | 1999 |
| New Chef Cottage Takeaway Ltd | Hospitality | 2022 |
| Next Level Spray Shop Ltd | Construction | 2024 |
| Nicholas John Haynes Limited | Extraterritorial | 2022 |
| Nicksas Holdings Limited | Financial services | 2014 |
| Nimrod Sound Limited | Information & communication | 2015 |
| NJC Landscaping Ltd | Administrative & support | 2025 |
| NO.11 Sheep Street Management Limited | Households | 2024 |
| Nobletech Limited | Manufacturing | 2000 |
| Noemi Rita Varia Ltd | Other services | 2017 |
| North East Cotswold Farmer Cluster CIC | Agriculture & fishing | 2021 |
| North South Land Limited | Mining & quarrying | 2025 |
| Norton Driving Services Limited | Other services | 2013 |
| Notting Hill Group Limited | Extraterritorial | 2024 |
| Noventrex Ltd | Information & communication | 2026 |
| NOW Marine Limited | Manufacturing | 2020 |
| Nuform Carpentry and Joinery Limited | Manufacturing | 2016 |
| O.G.P. Trading Ltd | Hospitality | 2020 |
| Oak ST Ltd | Professional & scientific | 2020 |
| Oak Windows & Doors Limited | Manufacturing | 2012 |
| Oaklea Management Ltd | Real estate | 2019 |
| Oakview Business Investments Ltd | Professional & scientific | 2013 |
| Oakwood Property Management Limited | Real estate | 1996 |
| Oathill Quarry Limited | Extraterritorial | 2015 |
| Obfx.Net Ltd | Administrative & support | 2011 |
| OIL Fuel Poverty Solutions Limited | Administrative & support | 2013 |
| OK10 Brick Stone&Block Work Ltd | Construction | 2018 |
| Oliveri Barbers Ltd | Other services | 2024 |
| Onboard Consulting Limited | Information & communication | 2002 |
| One Day I'Ll BE Able to Live OFF My Artistic Ventures Ltd | Arts & recreation | 2011 |
| One Hundred Ways Limited | Professional & scientific | 2022 |
| Opalstone Group Limited | Administrative & support | 2020 |
| Oppercom Ltd | Professional & scientific | 2025 |
| Opumo Limited | Wholesale & retail | 2011 |
| Orava Capital Ltd | Real estate | 2026 |
| Ordinal Research Limited | Professional & scientific | 2026 |
| Oriental and Western Limited | Wholesale & retail | 2011 |
| Overdale Equestrian Limited | Education | 2024 |
| Owen Mumford Holdings Limited | Financial services | 1955 |
| Owen Mumford Limited | Manufacturing | 1976 |
| Owen Mumford Technology Limited | Extraterritorial | 2016 |
| OX Cars Limited | Wholesale & retail | 2023 |
| Oxford Bearings Holdings (2000) Limited | Extraterritorial | 1999 |
| Oxford Bearings Limited | Wholesale & retail | 1994 |
| Oxford Bearings Properties Limited | Real estate | 2008 |
| Oxford Civil Engineering Company Limited | Construction | 2004 |
| Oxford DRY Stone Academy Ltd | Other services | 2020 |
| Oxford DRY Stone Walling Ltd | Administrative & support | 2018 |
| Oxford Infant Clinic Limited | Health & social care | 2020 |
| Oxford Interdec Limited | Construction | 2022 |
| Oxford International Associates Limited | Professional & scientific | 1988 |
| Oxford International Finance Limited | Financial services | 2017 |
| Oxford Medical Recruitment Services Ltd | Administrative & support | 2015 |
| Oxford Organics Limited | Wholesale & retail | 2011 |
| Oxford Planters Limited | Manufacturing | 2004 |
| Oxford Plastic Systems (Holdings) Limited | Extraterritorial | 2013 |
| Oxford Plastic Systems International Limited | Financial services | 2017 |
| Oxford Plastic Systems Limited | Manufacturing | 1985 |
| Oxford Publishing Ventures Ltd | Information & communication | 2012 |
| Oxford Spanish Ltd | Education | 2022 |
| Oxford Specialist Coachbuilders Limited | Administrative & support | 2012 |
| Oxford Technology & Media Limited | Administrative & support | 2014 |
| Oxford Technology Development Ltd | Professional & scientific | 2014 |
| Oxford Vacuum Science Limited | Manufacturing | 2004 |
| Oxford Walking Tours Limited | Administrative & support | 2015 |
| Oxford Wheels Ltd | Wholesale & retail | 2024 |
| Oxfordshire Building Safety Association Limited | Extraterritorial | 1985 |
| Oxfordshire Quarry Group Limited | Real estate | 1997 |
| Oxgarth Limited | Professional & scientific | 2015 |
| Oxie Holdings Ltd | Education | 2025 |
| P D Clarke Building Contractors Limited | Construction | 2019 |
| P.Peros Property Management Limited | Real estate | 1994 |
| Panoramic Journeys Limited | Administrative & support | 2003 |
| Papacat Limited | Hospitality | 2015 |
| Park Fair Great TEW Ltd | Administrative & support | 2022 |
| Parsonage Farm Holdings (Salford) Limited | Agriculture & fishing | 2022 |
| Party in Your Mouth Ltd | Hospitality | 2023 |
| Pathwys Ltd | Information & communication | 2026 |
| Paul Farrell Plumbing & Heating Ltd | Construction | 2014 |
| Paul Holberton Publishing Ltd | Information & communication | 2004 |
| Paul Selway Ltd | Construction | 2012 |
| Pawsonal Treasures Limited | Wholesale & retail | 2025 |
| PBM Endeavours Ltd | Professional & scientific | 2016 |
| Pbsp Limited | Information & communication | 2016 |
| PD TB Limited | Professional & scientific | 2023 |
| Peach Consulting Limited | Professional & scientific | 2019 |
| Peak Performance Therapies Ltd | Health & social care | 2008 |
| Pease & Associates Ltd | Professional & scientific | 2019 |
| Pease Consultants Limited | Professional & scientific | 2000 |
| Pease Holding Limited | Professional & scientific | 2020 |
| Pebble Ultrasound Ltd | Health & social care | 2025 |
| Pegasus Technical Solutions Ltd | Professional & scientific | 2013 |