| OTP Events Ltd | Administrative & support | 2021 |
| Otter Dotter Ltd | Wholesale & retail | 2023 |
| Oualie Botanicals Ltd | Wholesale & retail | 2020 |
| Oura Limited | Education | 2016 |
| Outer Town Festival Ltd | Arts & recreation | 2024 |
| Overstrung Ltd | Information & communication | 2015 |
| Owen Charles Ltd | Other services | 2014 |
| Owlvale Limited | Professional & scientific | 1999 |
| OX. Assisted Reproduction Limited | Information & communication | 2020 |
| OX. General Practice Ltd | Information & communication | 2020 |
| OX. Patient Consent Limited | Information & communication | 2022 |
| OX. Patient Referral Limited | Information & communication | 2022 |
| OX. Pregnancy & Maternity Limited | Information & communication | 2020 |
| OX. Virtual Clinic Limited | Health & social care | 2020 |
| OX. Waiting Room Limited | Information & communication | 2022 |
| Oxacus Ltd | Professional & scientific | 2019 |
| OXC Group Limited | Manufacturing | 2012 |
| Oxdh Limited | Professional & scientific | 2020 |
| Oxford 7 Property Limited | Extraterritorial | 2008 |
| Oxford Accountant Ltd | Professional & scientific | 2011 |
| Oxford Aerials Limited | Construction | 2009 |
| Oxford Algorithmics Ltd. | Information & communication | 2013 |
| Oxford Blue Building Services Ltd | Construction | 2020 |
| Oxford Carp Baits Limited | Wholesale & retail | 2024 |
| Oxford Cognition Limited | Health & social care | 2015 |
| Oxford Geospatial Limited | Construction | 2006 |
| Oxford Micromedical Limited | Manufacturing | 2012 |
| Oxford Plumbing Company Ltd | Construction | 2023 |
| Oxford Scientific Consultants Limited | Professional & scientific | 1987 |
| Oxford Seating Company Limited | Manufacturing | 2015 |
| Oxford Spires Joinery Limited | Manufacturing | 2018 |
| Oxford Summer Programmes Limited | Education | 2017 |
| Oxford Ultimate Cleaning Limited | Administrative & support | 2022 |
| Oxfordshire Associate Services Limited | Health & social care | 2015 |
| Oxfordshire Early Years Ltd | Health & social care | 2026 |
| Oxfordshire Groundworks Ltd | Construction | 2023 |
| P & J Developments Limited | Real estate | 1999 |
| P1VITAL Limited | Professional & scientific | 2004 |
| P1VITAL Products Limited | Professional & scientific | 2010 |
| Paincure UK Limited | Health & social care | 2024 |
| Pallas Software Group Ltd | Administrative & support | 2025 |
| Panam Ltd. | Professional & scientific | 1959 |
| Pandrup SVS Limited | Information & communication | 2014 |
| Papaya House of London Ltd | Wholesale & retail | 2018 |
| Paraxerve Limited | Administrative & support | 2019 |
| Pathfinder Partners Limited | Information & communication | 1999 |
| Pathos Healthcare Research Limited | Extraterritorial | 2021 |
| Pathos Limited | Extraterritorial | 2021 |
| Pathos Research Limited | Extraterritorial | 2021 |
| Paul Clewlow & Co Ltd | Professional & scientific | 2003 |
| Paul Glynn Consulting Ltd | Professional & scientific | 2025 |
| Paul Hicks Limited | Construction | 2009 |
| Paul Richardson Consultancy and Training Services Limited | Professional & scientific | 2012 |
| PC Technicians Limited | Other services | 2003 |
| Pennefather Films Ltd | Information & communication | 2016 |
| Performance Enclosures Limited | Manufacturing | 1991 |
| Period Home Projects Limited | Construction | 2015 |
| Perioservices Limited | Health & social care | 2013 |
| Perkin Properties Limited | Real estate | 2021 |
| Permanent Pothole Solutions Ltd | Construction | 2026 |
| Pest Wizards Limited | Other services | 2023 |
| Petal and Herb Ltd | Manufacturing | 2024 |
| PFP Surveying & Consulting Ltd | Construction | 2021 |
| Pharma Business Solutions Limited | Professional & scientific | 1999 |
| Phyllis Earle Limited | Wholesale & retail | 1921 |
| Pimc Limited | Information & communication | 2000 |
| Pitufo Properties Limited | Real estate | 2013 |
| PJ Emjay Limited | Information & communication | 2023 |
| Planet Land Consultants Limited | Professional & scientific | 2016 |
| Plastic Head Media Limited | Arts & recreation | 2005 |
| Plastic Head Music Distribution Limited | Arts & recreation | 1988 |
| Plian Limited | Professional & scientific | 2007 |
| Polkadot Parsley Ltd | Wholesale & retail | 2026 |
| Pollution Monitors Limited | Manufacturing | 1986 |
| Polypump Limited | Manufacturing | 2003 |
| Portarlington (U.K.) Limited | Real estate | 1996 |
| Portarlington Holdings Limited | Financial services | 2017 |
| Poseidon Heating Engineers Limited | Other services | 2019 |
| Posh Concrete Limited | Construction | 2018 |
| PPM Environmental Limited | Administrative & support | 2016 |
| Praesidium Property and Travel Ltd | Real estate | 2000 |
| Praxis BA Limited | Professional & scientific | 1995 |
| Praxismap Ltd | Professional & scientific | 2025 |
| Pre-School Admin Angels Limited Liability Partnership | | 2006 |
| Precise Solutions Group UK Limited | Manufacturing | 2025 |
| Precision Quality Consulting Limited | Professional & scientific | 2004 |
| Predawn Limited | Financial services | 1986 |
| Premier Animal Housing Limited | Other services | 2012 |
| Presolana Enterprise Ltd | Hospitality | 2024 |
| Prickly Pear Growth Limited | Professional & scientific | 2025 |
| Privy JET Consultancy Limited | Transport & logistics | 2023 |
| Pro-Gen Diagnostics Limited | Health & social care | 2023 |
| PRO4ORM Hcps Ltd | Administrative & support | 2026 |
| Profcomp Productions Limited | Information & communication | 2009 |
| Project Setting OUT Limited | Construction | 2015 |
| PROMANAGE13 Limited | Construction | 2021 |
| Prooven Cleaning Limited | Administrative & support | 2010 |
| Proteacea Digital Solutions Ltd | Information & communication | 2025 |
| Proudfoot Pictures Ltd | Professional & scientific | 2013 |
| Proxima Property Ltd | Households | 2024 |