| Ossium Health Ltd | Health & social care | 2026 |
| Ostadmart Ltd | Information & communication | 2023 |
| Oswald Mews Limited | Extraterritorial | 2011 |
| OT by the Sea Ltd | Extraterritorial | 2022 |
| OTA Media Limited | Information & communication | 2025 |
| Othniel Properties Ltd | Households | 2025 |
| OTT Fitness Ltd | Arts & recreation | 2025 |
| Otway Capital Limited | Hospitality | 2020 |
| Otway Hotels Limited | Hospitality | 2020 |
| OUD and Co Limited | Wholesale & retail | 2025 |
| OUR Place to Make CIC | Education | 2026 |
| OUR Special Friends | Other services | 2013 |
| Oura Scent Ltd | Wholesale & retail | 2026 |
| OUT & OUT Safety Ltd | Administrative & support | 2023 |
| OUT of Mexico Limited | Wholesale & retail | 2003 |
| OUT There Orders Ltd | Wholesale & retail | 2026 |
| Out-Space C.I.C. | Education | 2024 |
| Outback Kamper Ltd | Manufacturing | 2022 |
| Outbackautos Ltd | Wholesale & retail | 2024 |
| Outdoor Quest Ltd. | Arts & recreation | 2023 |
| Outdoorbeanbag.Com Limited | Manufacturing | 2008 |
| Outer Commission Limited | Professional & scientific | 2020 |
| Outerlink AI Limited | Information & communication | 2024 |
| Outfit Connect Ltd | Wholesale & retail | 2020 |
| Outfitvibe Ltd | Wholesale & retail | 2026 |
| Outlet Designer Ltd | Wholesale & retail | 2025 |
| Outmotive Ltd | Information & communication | 2025 |
| Outofhours IT Support Ltd | Information & communication | 2026 |
| Outram Investments Limited | Real estate | 2012 |
| Outside the Blocks Ltd | Manufacturing | 2024 |
| Outstanding.Global Ltd | Administrative & support | 2019 |
| Ovachopp Ltd | Hospitality | 2025 |
| Ovayolu Limited | Professional & scientific | 2015 |
| Oven & Whisk Ltd | Manufacturing | 2025 |
| Overgrown Hospitality Ltd | Hospitality | 2025 |
| Overlay Apps Ltd | Information & communication | 2020 |
| Overy Traction Ltd | Transport & logistics | 2025 |
| OWA Global Ltd | Wholesale & retail | 2024 |
| Owen Tech Consulting Limited | Information & communication | 2026 |
| Owls Bay Ltd | Wholesale & retail | 2025 |
| OWP Online Ltd | Wholesale & retail | 2025 |
| Ox-C Machine Tool Services Ltd | Manufacturing | 2016 |
| Oxbridged Ltd | Education | 2025 |
| Oxford Biodiversity Research Limited | Professional & scientific | 2023 |
| Oxford Capital Services Limited | Professional & scientific | 2023 |
| Oxford Circus Ltd | Professional & scientific | 2021 |
| Oxford Insure Limited | Information & communication | 2023 |
| Oxford Medtech Ltd | Professional & scientific | 2024 |
| Oxfordshire Construction Group Ltd | Financial services | 2024 |
| Oxguide Ltd | Information & communication | 2025 |
| Oxley Hughes Limited | Administrative & support | 2012 |
| Oxus Electrical Ltd | Construction | 2025 |
| Oyster Wealth Management Limited | Professional & scientific | 2008 |
| OZ Trading Group Ltd | Wholesale & retail | 2020 |
| Ozeco Ltd | Wholesale & retail | 2024 |
| Ozoite Ltd | Wholesale & retail | 2023 |
| Ozzli Ltd | Administrative & support | 2025 |
| O’Brien Consulting Services Limited | Professional & scientific | 2025 |
| P & E Music Limited | Information & communication | 1990 |
| P & J Textiles Limited | Wholesale & retail | 1996 |
| P & R Seeds Limited | Wholesale & retail | 2018 |
| P & S Equestrian Ltd | Arts & recreation | 2014 |
| P Flack Associates Limited | Professional & scientific | 2015 |
| P J COX Limited | Financial services | 2023 |
| P J Music Limited | Information & communication | 1981 |
| P Jacobs Consulting Limited | Professional & scientific | 2015 |
| P K M Solutions Limited | Manufacturing | 2008 |
| P Lewis Trading Ltd | Wholesale & retail | 2008 |
| P R Hobbs Ltd | Construction | 2012 |
| P&P Retail Management Limited | Wholesale & retail | 2025 |
| P.B.A. Engineering Ltd. | Manufacturing | 1997 |
| P2B Properties Ltd | Real estate | 2025 |
| P31 Ltd | Extraterritorial | 2018 |
| P4TT3RN3D Ltd | Wholesale & retail | 2025 |
| Pacific Digital Solutions Ltd | Information & communication | 2025 |
| Packageware Ltd | Information & communication | 2022 |
| PAD Sustainability Ltd | Real estate | 2023 |
| Padeja Ltd | Information & communication | 2026 |
| Page & SON Limited | Wholesale & retail | 1961 |
| Page Hero Ltd | Information & communication | 2025 |
| Pairs Wholesale Limited | Wholesale & retail | 2026 |
| Pakenham Consulting Limited | Professional & scientific | 2011 |
| Pakt Consulting Limited | Professional & scientific | 2017 |
| Palace Solicitors Limited | Professional & scientific | 2024 |
| Palatial Staging Ltd | Real estate | 2025 |
| Palletsam Clearance Services Ltd | Other services | 2012 |
| Palletsam Worldwide Logistics Ltd | Other services | 2012 |
| Palm Digital Limited | Financial services | 2019 |
| Palm Isla Travel Ltd | Administrative & support | 2025 |
| Palm Solutions FM Ltd | Water & waste | 2018 |
| Palmer Brickworks Ltd | Construction | 2019 |
| Palmer Dollar Finance | Financial services | 2006 |
| Palmer Finance | Financial services | 2004 |
| Palmer YEN Finance | Financial services | 2008 |
| Pampisford Renovations Limited | Construction | 2012 |
| Pam’S Investment Properties Limited | Real estate | 2018 |
| Panacea Property Group Ltd | Real estate | 2023 |
| Pancake Math Ltd | Information & communication | 2026 |
| Pancho Training & Consultancy Limited | Professional & scientific | 1997 |
| Panecom Services Ltd | Information & communication | 2023 |