| OUR Wellbeing Collective CIC | Education | 2026 |
| Ouse Energy (Holdings) Limited | Financial services | 2022 |
| Out-Com-Solutions Limited | Professional & scientific | 2018 |
| Outdoor Woodland Wellness Ltd | Other services | 2021 |
| Outhaus Limited | Wholesale & retail | 2013 |
| Outsource Your Office Ltd | Administrative & support | 2018 |
| Outspark Ltd | Arts & recreation | 2014 |
| OVA Nova Limited | Financial services | 2025 |
| Ovadose Creations Ltd | Professional & scientific | 2019 |
| Ovearo Ltd | Information & communication | 2023 |
| Ovenden Medical Ltd | Health & social care | 2025 |
| Over Extraction Limited | Financial services | 2022 |
| Over the Edge Media Ltd | Information & communication | 2026 |
| Oversite Technology Ltd | Information & communication | 2026 |
| Ovistar Media Entertainment Ltd. | Wholesale & retail | 2015 |
| OW Mead Consulting Limited | Financial services | 2024 |
| Owen Ridgwell Plumbing and Heating Ltd | Construction | 2025 |
| OWL Professional Services Limited | Other services | 2016 |
| OWR Communications Ltd | Professional & scientific | 2025 |
| Oxbury & Company Limited | Professional & scientific | 2003 |
| Oxfordshire Property Development Limited | Construction | 2022 |
| Oxygen Digital Recruitment Limited | Administrative & support | 2017 |
| Oxygen House Wellness Ltd | Other services | 2026 |
| Oyiyo Services Limited | Administrative & support | 2021 |
| Oyster Accountants Ltd | Professional & scientific | 2011 |
| Oysterblink Real Estates and Investments Ltd | Real estate | 2015 |
| Oysterblink UK Ltd | Manufacturing | 2010 |
| Oysterweb Ltd | Manufacturing | 2024 |
| Ozgur Miran Ltd | Wholesale & retail | 2016 |
| Ozzy Holdings Ltd | Construction | 2024 |
| Ozzy Properties Ltd | Real estate | 2026 |
| P & a Fairhurst Limited | Construction | 2008 |
| P & B Furniture Supplies Limited | Manufacturing | 2012 |
| P & J Fairman Group Ltd | Financial services | 2023 |
| P & LA Limited | Real estate | 2020 |
| P B Roofing Services Limited | Construction | 2026 |
| P Butler Plumbing & Heating Ltd | Construction | 2024 |
| P Cassettari Limited | Administrative & support | 2003 |
| P Connolly Construction Limited | Construction | 2012 |
| P F E Electrical Limited | Construction | 2014 |
| P J Education Ltd | Professional & scientific | 2017 |
| P J Lawn and Daughters Limited | Construction | 2019 |
| P J M Building & Maintenance Limited | Other services | 2008 |
| P J Property Ltd | Real estate | 2006 |
| P M C Sports & Leisure Ltd | Wholesale & retail | 2002 |
| P O a Auto Spray Centre Ltd | Manufacturing | 2026 |
| P P Attractions Limited | Administrative & support | 2018 |
| P R Chapman & Sons Limited | Real estate | 2023 |
| P Woulfe & SON Ltd. | Construction | 1993 |
| P&B Associates Ltd | Manufacturing | 2016 |
| P&D Electrical Solutions Ltd | Construction | 2016 |
| P&P Quickfix Ltd | Manufacturing | 2026 |
| P-Czek Services Limited | Information & communication | 2018 |
| P. L. Stevens Limited | Manufacturing | 2002 |
| P.B.Ceilings & Partitions Limited | Construction | 2005 |
| P.G. Philpot & SON (Dollymans) Limited | Real estate | 1945 |
| P.G. Philpot & SON (Farms) Limited | Extraterritorial | 1995 |
| P.G. Philpot & SON (Holdings) Limited | Professional & scientific | 1987 |
| P.J. Accident Repair Centre Limited | Wholesale & retail | 2019 |
| P.J. Weller & SON (Holdings) Limited | Real estate | 1943 |
| P.L.K. Consulting Limited | Information & communication | 2007 |
| P.Mccarthy Project Management Ltd | Construction | 2021 |
| P.P.C. Tiling Limited | Construction | 1996 |
| P.R. Retail Consultants Limited | Administrative & support | 2005 |
| P4M Private Ltd | Information & communication | 2016 |
| PA & IT Solutions Limited | Administrative & support | 2010 |
| Paaa Investments Limited | Real estate | 2023 |
| PACE50 Property Limited | Real estate | 2018 |
| Pack Fulfilment Limited | Transport & logistics | 2018 |
| Pactel Solutions Ltd | Information & communication | 2002 |
| Paddocks Ongar Management Company Limited | Households | 2026 |
| Padelwise Limited | Arts & recreation | 2020 |
| PAE Management Ltd | Administrative & support | 2010 |
| Page Engineering Consultancy Ltd | Construction | 2025 |
| Paget Somers & Morgan Ltd | Professional & scientific | 2023 |
| Paget Somers Financial Services Ltd | Professional & scientific | 2016 |
| PAI & PAI Ltd | Health & social care | 2026 |
| Paint Prestige Limited | Construction | 2022 |
| PAINT2K Limited | Wholesale & retail | 2020 |
| Pakanati and Sons Private Ltd | Wholesale & retail | 2026 |
| Pakwheels Ltd | Wholesale & retail | 2019 |
| Palace Kitchens Ltd | Extraterritorial | 2018 |
| Palace Media Limited | Information & communication | 2014 |
| Palewell Golf & Tennis Limited | Real estate | 1996 |
| Palmer Holdings Limited | Financial services | 2002 |
| Palmer Investment Management Limited | Financial services | 2007 |
| Pals Ltd | Health & social care | 2006 |
| PAM Auto Trading Limited | Wholesale & retail | 2018 |
| PAM Foodservice Ltd | Hospitality | 2020 |
| PAM Prime Ltd | Wholesale & retail | 2024 |
| Pamper Pamper Ltd | Administrative & support | 2009 |
| Panacea Interiors Ltd. | Construction | 2015 |
| Panada Services Ltd | Health & social care | 2021 |
| Pandedomena Limited | Professional & scientific | 2018 |
| Pangea UK Bidco Limited | Financial services | 2024 |
| Pangea UK Holdco Limited | Financial services | 2024 |
| Panibee Ltd | Professional & scientific | 2013 |
| Pankajini Ltd | Information & communication | 2017 |
| Panners Investments Ltd | Real estate | 2013 |
| Pantheon Protect Limited | Financial services | 2023 |