| Orchard Gate (Beaconsfield) Management Company Limited | Households | 1992 |
| Orchard Parade Limited | Real estate | 2017 |
| Orchard Way Community Group Ltd | Real estate | 2021 |
| Orchard West Limited | Real estate | 2025 |
| ORCHESTR8 Limited | Professional & scientific | 2002 |
| Orchid House Limited | Construction | 1989 |
| Origami Risk Ltd | Information & communication | 2015 |
| Orin Fine Ltd | Manufacturing | 2026 |
| Ormonde Residents Association Limited | Households | 1980 |
| Orran Consulting Limited | Professional & scientific | 2023 |
| Orsus Project Surveyors Ltd | Professional & scientific | 2020 |
| Oryx Fuel Systems Ltd | Professional & scientific | 2025 |
| OSI Ltd | Professional & scientific | 2016 |
| Ostylish Ltd | Other services | 2026 |
| OTB Concrete Limited | Construction | 2008 |
| Othee Group Ltd | Construction | 2017 |
| Ototo Limited | Information & communication | 2025 |
| OUT of Home Capital Limited | Professional & scientific | 2020 |
| Outdoor Media Advisory Limited | Professional & scientific | 2008 |
| Outside Voice Media Ltd | Information & communication | 2025 |
| Owen Ventures Limited | Financial services | 2015 |
| Owncontrol Property Management Limited | Households | 1994 |
| OX Capital Investments Limited | Financial services | 2017 |
| Oxbridge Global Tutors Ltd | Education | 2013 |
| Oxbridge Mind Ltd | Education | 2023 |
| Oxcyber CIC | Other services | 2023 |
| Oxford Building Maintenance Limited | Construction | 2020 |
| Oxford Clinical Neuropsychology Services Limited | Health & social care | 2013 |
| Oxford Oak Garages Ltd | Construction | 2021 |
| Oxhack Limited | Administrative & support | 2026 |
| Oyster Shell Properties Limited | Real estate | 2023 |
| P & N Property Estates Ltd | Real estate | 2023 |
| P. E. Mead & Sons Holdings Limited | Financial services | 2026 |
| P. E. Mead & Sons Limited | Agriculture & fishing | 2015 |
| P. Wellfair (Holdings) Limited | | 1964 |
| P2 Investment Properties Limited | Real estate | 2020 |
| Pabs Audio Limited | Information & communication | 2014 |
| Paccship (UK) Limited | Transport & logistics | 2001 |
| PAD Surfaces Limited | Manufacturing | 2021 |
| Paige Europe Limited | Financial services | 2018 |
| Paint by Numbers Limited | Information & communication | 2016 |
| Palatine (Ledborough Gate) Limited | Households | 2024 |
| Palatine Homes Ltd | Construction | 2013 |
| Palatine Johnson Drive Ltd | Households | 2024 |
| Palida Ltd | Professional & scientific | 2021 |
| PAM Technology Limited | Information & communication | 2023 |
| Panache Building Management Limited | Real estate | 2017 |
| Panache Design & Developments Limited | Real estate | 2017 |
| Panache Group Limited | Financial services | 2019 |
| Panazee Ltd | Professional & scientific | 2024 |
| PANDA88 Investments Ltd | Real estate | 2021 |
| Paramount Audio Visual LLP | | 2023 |
| Paramount Management Company Limited | Administrative & support | 1997 |
| Parc Education Limited | Professional & scientific | 2021 |
| Park Mews Bushey Management Company Limited | Households | 2015 |
| Park Secretarial Services Limited | Professional & scientific | 1987 |
| Park View Realty Ltd | Real estate | 2023 |
| Park-Exeter Ltd | Real estate | 2002 |
| Parklife Group Limited | Real estate | 2016 |
| Parklife Silverstone Limited | Real estate | 2023 |
| Parkstone Vehicle Services Limited | Administrative & support | 2020 |
| Parnells Holdings Ltd | Wholesale & retail | 2007 |
| Parrot & Palm Ltd | Administrative & support | 2021 |
| Parsonage Place Management Company (NO. 2) Limited | Real estate | 2010 |
| Patchwork Gates Ltd | Real estate | 2020 |
| Patek Philippe Salon Limited | Administrative & support | 2005 |
| Pathway Biosolutions Ltd | Professional & scientific | 2023 |
| Patsy Blunt Interiors Limited | Professional & scientific | 2010 |
| Paul Donnelly Services Limited | Arts & recreation | 2021 |
| Paul Gardam TV Ltd | Information & communication | 2017 |
| Paul Moran Productions Ltd | Arts & recreation | 2013 |
| Paul Slais Limited | Administrative & support | 2021 |
| PB4 Ltd | Information & communication | 2023 |
| PBU Investments Limited | Professional & scientific | 2026 |
| PDP Consultancy Services Ltd | Professional & scientific | 2015 |
| Peaar Limited | Professional & scientific | 2020 |
| Peacock Inc. Limited | Administrative & support | 2015 |
| Peak Gateway Properties Limited | Construction | 2021 |
| Peake Property Holdings Ltd | Construction | 2025 |
| Pearson Douglas Ltd | Professional & scientific | 2014 |
| Peblor Limited | Information & communication | 2026 |
| Peckham Spring Limited | Extraterritorial | 2025 |
| Pegasus I LLP | | 2022 |
| Pendleton Associates LLP | | 2002 |
| Penn Assured Property Ltd | Real estate | 2019 |
| Penn House Residents Limited | Households | 1989 |
| Penn Leisure Limited | Hospitality | 1994 |
| Pennington Support Limited | Education | 2021 |
| Pennview Investment Company | Professional & scientific | 2025 |
| Pennyworth Place (Beaconsfield) Management Company Limited | Households | 2020 |
| Penryn Developments Limited | Real estate | 2009 |
| Pension Savings Investment Annuity Mortgage LLP | | 2012 |
| Pentacle Limited | Professional & scientific | 1993 |
| Pentacle Works Limited | Extraterritorial | 1999 |
| Pentagon Global Alliance Limited | Financial services | 2022 |
| Pentagon Property Partnerships Limited | Other services | 2017 |
| Pentagon Technical Holdings Limited | Financial services | 2024 |
| Pentagon Technical Services Ltd | Professional & scientific | 2021 |
| Pentheus Holdings Limited | Professional & scientific | 2023 |
| Peony Scarlett Ltd | Wholesale & retail | 2017 |