| Orbital Integrations Limited | Information & communication | 2022 |
| Orchard 100 Holdings Limited | Financial services | 2022 |
| Orchard Lettings Limited | Real estate | 1997 |
| Ordnance Property Ltd | Construction | 2019 |
| Organic Marketing Services Limited | Professional & scientific | 2022 |
| Organic Sauna Session Limited | Health & social care | 2026 |
| Organic Vuplex Limited | Wholesale & retail | 2026 |
| Oriel Court (Plot 9) Limited | Real estate | 1993 |
| Origio Limited | Professional & scientific | 1996 |
| Oriole Bibemi Limited | Mining & quarrying | 2024 |
| Oriole Limestone Limited | Financial services | 2024 |
| Oriole MBE Limited | Financial services | 2024 |
| Oriole Resources PLC | Mining & quarrying | 2005 |
| Orion Homecare Management Ltd | Public administration | 2025 |
| Ormskirk Specsavers Hearcare Limited | Wholesale & retail | 2022 |
| Ormskirk Specsavers Limited | Wholesale & retail | 2002 |
| Orpington Specsavers Hearcare Limited | Wholesale & retail | 2006 |
| Orpington Specsavers Limited | Wholesale & retail | 1996 |
| Orriss Consultancy Limited | Professional & scientific | 2019 |
| Ortex Technologies Ltd | Financial services | 2017 |
| Orthodontica Limited | Health & social care | 2017 |
| Ortum Futures Ltd | Construction | 2022 |
| Orwell Dredging Ltd | Construction | 2025 |
| OS Beauty LAB Limited | Other services | 2025 |
| OS Construction Services Ltd | Construction | 2026 |
| OS3 Digital Platform Limited | Information & communication | 2009 |
| Osashi Ltd | Real estate | 2020 |
| OSASHI2 Ltd | Construction | 2023 |
| Osavie Properties Ltd | Real estate | 2024 |
| Osborne House RTM Company Limited | Households | 2004 |
| OSP Retail Limited | Professional & scientific | 2014 |
| Oswestry Specsavers Limited | Wholesale & retail | 2001 |
| OTC Skin Care Ltd | Wholesale & retail | 2019 |
| Otley Specsavers Hearcare Limited | Wholesale & retail | 2019 |
| Otley Specsavers Limited | Wholesale & retail | 2006 |
| Otley Visionplus Limited | Wholesale & retail | 2006 |
| Otso Creative Limited | Other services | 2014 |
| OUR Home Hero Limited | Construction | 2025 |
| OUR LSS Co. Ltd | Extraterritorial | 2022 |
| OUR MEP Co. Ltd | Construction | 2021 |
| OUR Property Co. Ltd | Construction | 2022 |
| Outdoor Life Landscapes Ltd | Administrative & support | 2016 |
| Overthinking Limited | Professional & scientific | 2025 |
| Owen Property Services Ltd | Real estate | 2025 |
| Owen Reeman Ltd | Information & communication | 2025 |
| OWG Cars Ltd | Wholesale & retail | 2020 |
| Oxford Engineering (Hampshire) Limited | Manufacturing | 2007 |
| Oxford Specsavers Hearcare Limited | Wholesale & retail | 2017 |
| Oxford Specsavers Limited | Wholesale & retail | 2004 |
| Oxford Visionplus Limited | Wholesale & retail | 2004 |
| Oxfordshire Newmedica Limited | Health & social care | 2021 |
| Oxted Specsavers Limited | Wholesale & retail | 2018 |
| P & C Construction Twickenham Ltd | Construction | 2014 |
| P & C Developments Twickenham Ltd | Construction | 2020 |
| P & S Plastering Limited | Construction | 2009 |
| P 2 Controllers Ltd | Information & communication | 1985 |
| P a Dental LAB Services Ltd | Health & social care | 2020 |
| P City Grill Ltd | Hospitality | 2025 |
| P Gain Properties Limited | Real estate | 2026 |
| P H Carpets & Flooring Services Limited | Wholesale & retail | 2000 |
| P J Attwood Limited | Professional & scientific | 2023 |
| P J C Properties (Southampton) Limited | Real estate | 1999 |
| P Mcdonald Limited | Construction | 2001 |
| P Mcgrath Solutions Limited | Financial services | 2013 |
| P Surridge Limited | Construction | 2002 |
| P&D’S Place Ltd | Real estate | 2025 |
| P&J Accounting Services Limited | Professional & scientific | 2019 |
| P&P Contracts Ltd | Construction | 2025 |
| P&P Direct Ltd | Wholesale & retail | 2026 |
| P-Tol Holdings Limited | Administrative & support | 2022 |
| P. Fitzsimmons Limited | Water & waste | 2002 |
| P.P.D.S Limited | Administrative & support | 2004 |
| P3Q Consulting Ltd | Information & communication | 2014 |
| Pabari Properties Limited | Real estate | 2015 |
| Packet BEE Ltd | Information & communication | 2020 |
| Packet Star Networks Limited | Information & communication | 2016 |
| Packham Holdings Limited | Real estate | 2024 |
| Paddington Green Propco Limited | Construction | 2018 |
| Page Electrical Installations Ltd | Construction | 2023 |
| Pagemill Limited | Real estate | 2000 |
| Pagham Homes Ltd | Construction | 2020 |
| PAH Building & Construction Limited | Construction | 2010 |
| Paignton Specsavers Hearcare Limited | Wholesale & retail | 2018 |
| Paines Finance Solutions Ltd | Financial services | 2023 |
| Paint Inspection Ltd | Construction | 2010 |
| Paint Technology Solutions Limited | Information & communication | 2011 |
| Paint Works (International) Limited | Manufacturing | 2013 |
| Painted Palms Ltd | Education | 2024 |
| Pairview Limited | Information & communication | 2009 |
| Paisley Specsavers Limited | Wholesale & retail | 1991 |
| Paisley Visionplus Limited | Wholesale & retail | 2001 |
| Palatinate Consulting Limited | Professional & scientific | 2012 |
| Palletmove Limited | Transport & logistics | 2016 |
| Pallets Direct Limited | Transport & logistics | 2018 |
| Palm Acres Ltd | Real estate | 2024 |
| Palmer Communications Limited | Professional & scientific | 2023 |
| Palmer Joinery Ltd | Construction | 2009 |
| Palmers Green Specsavers Limited | Wholesale & retail | 2006 |
| Palmers Green Visionplus Limited | Wholesale & retail | 2006 |
| Palmerston Indoor Bowls Club Limited | Arts & recreation | 1996 |