| OKL Equestrian LLP | | 2017 |
| Old Berkshire Hunt Limited | Agriculture & fishing | 2004 |
| Old George (South Cerney) Limited | Hospitality | 2011 |
| Old Mill Cottages Ltd | Hospitality | 2022 |
| Oldfield Business Services Limited | Professional & scientific | 1992 |
| Oldfield Property Holdings LLP | | 2006 |
| OLI Christie Ltd | Administrative & support | 2023 |
| OLL Limited | Construction | 2015 |
| Olva Limited | Administrative & support | 2024 |
| Omnimax Media Limited | Information & communication | 2021 |
| ON the Wall Interiors Ltd | Wholesale & retail | 2025 |
| Onamishun Limited | Professional & scientific | 2017 |
| Onarray Ltd | Information & communication | 2013 |
| One Step Foods Ltd | Manufacturing | 2024 |
| One Stop Cable Shop Limited | Extraterritorial | 2018 |
| Oninit Consulting Limited | Information & communication | 2005 |
| Online Padel Shop Limited | Information & communication | 2024 |
| Oops a Daisy Properties Limited | Financial services | 2022 |
| Opah Aviation Ltd | Transport & logistics | 2023 |
| Opportunity Shops (Purchasing) Limited | Wholesale & retail | 2014 |
| Optimized Ortho Limited | Professional & scientific | 2013 |
| Optimum Cctv Limited | Manufacturing | 1954 |
| Optimum Health Services Limited | Other services | 2005 |
| Optimum Mobility Limited | Wholesale & retail | 2014 |
| Options Supported Holidays Ltd | Administrative & support | 2003 |
| Opus Research Ltd | Administrative & support | 2022 |
| OR Occlude Ltd | Arts & recreation | 2024 |
| Orangestripe Outsourcing and Accountancy Limited | Professional & scientific | 2022 |
| Orbital Agriculture Technologies Ltd | Extraterritorial | 2025 |
| Orchard CL Limited | Hospitality | 2018 |
| Orchard Farm Property Limited | Agriculture & fishing | 2025 |
| Orchard Paddock Enterprises Limited | Administrative & support | 2005 |
| Ordnance Test Solutions Limited | Professional & scientific | 2004 |
| Orion Cotswolds Aviation Limited | Administrative & support | 2019 |
| Orion Holidays Limited | Other services | 1999 |
| Orla HR Limited | Professional & scientific | 2024 |
| Orsia Limited | Information & communication | 2026 |
| Orthotropic Engineering Ltd | Professional & scientific | 2018 |
| Osea Ltd | Real estate | 2020 |
| OSR Events and Promotions Ltd | Administrative & support | 2019 |
| Otterhouse Veterinary and Equine Services Ltd | Professional & scientific | 2017 |
| Otterluing Ltd | Health & social care | 2022 |
| Oude Ltd | Manufacturing | 2020 |
| OUR IT Services Limited | Information & communication | 2004 |
| Outside Studios Limited | Administrative & support | 2008 |
| OVA Retreats Ltd | Hospitality | 2026 |
| Oval Investments Limited | Financial services | 2011 |
| Overbrook Management Limited | Professional & scientific | 2012 |
| Ovix Limited | Information & communication | 2005 |
| Owais Investment Ltd | Real estate | 2021 |
| Owais Ltd | Health & social care | 2018 |
| Owen Whitehead Industries Ltd | Information & communication | 2024 |
| OWL Cottage Ltd | Hospitality | 2015 |
| OX Property Investments Ltd | Real estate | 2022 |
| Oxberg Ltd | Financial services | 2024 |
| Oxford Software Innovation Ltd | Professional & scientific | 2021 |
| Ozone Negotiation Limited | Professional & scientific | 2018 |
| P and a Haulage Ltd | Administrative & support | 2024 |
| P R Tiling Ltd | Construction | 2018 |
| PA Anywhere Limited | Information & communication | 2023 |
| Page 6 Limited | Information & communication | 2023 |
| Page Empire Limited | Real estate | 2020 |
| Pageworks Limited | Information & communication | 1997 |
| Paintworks INK Limited | Real estate | 2024 |
| Paintyard Limited | Real estate | 2001 |
| Palmer Plating Limited | Manufacturing | 1982 |
| PAN Global Plants Ltd | Wholesale & retail | 2013 |
| Panda Mobile (Cirencester) Ltd | Wholesale & retail | 2018 |
| Pannell Hayes Consulting Limited | Professional & scientific | 2016 |
| Papatango Theatre Company Ltd | Arts & recreation | 2010 |
| Pappo Sandwiches Ltd | Hospitality | 2024 |
| Parish of Cirencester Limited | Wholesale & retail | 1993 |
| Paritus Consulting Limited | Professional & scientific | 2014 |
| Park Blockley Limited | Construction | 2019 |
| Park Farm Syndicate (Fairford) Limited | Agriculture & fishing | 1936 |
| Park Lane PUP Ltd | Wholesale & retail | 2017 |
| Parlour Farm Kitchens & Cabinet Makers Ltd | Manufacturing | 2021 |
| Passmore & Chamberlain Ltd | Real estate | 2020 |
| Passmore Developments Limited | Real estate | 2018 |
| Paul Haresign Limited | Construction | 2002 |
| Paul Taylor Design Ltd | Professional & scientific | 2020 |
| Pavillion Collective Ltd | Other services | 2026 |
| Paxen Group Ltd | Professional & scientific | 2018 |
| Paxton Springs Limited | Water & waste | 2011 |
| Payfair Financial Services Ltd | Professional & scientific | 2025 |
| Payment Blueprints Ltd | Professional & scientific | 2018 |
| PCH Developments Ltd | Construction | 2013 |
| PCS-01 Limited | Real estate | 2018 |
| Peacefield Pubs Limited | Hospitality | 2012 |
| Peacekeeper (International) Limited | Administrative & support | 2011 |
| Peach Property Partners Ltd | Real estate | 2025 |
| Peachsoft Ltd | Wholesale & retail | 2023 |
| Peacock Electrical Limited | Construction | 2013 |
| Pearl's Procare Ltd | Health & social care | 2022 |
| Peels Events U.K. Ltd | Hospitality | 2024 |
| Peer Lime Specialist Ltd | Construction | 2020 |
| Pegasus Gloucester Planning Limited | Extraterritorial | 2010 |
| Pegasus Mobile Valeting Ltd | Administrative & support | 2023 |
| Pegasus Planning Group Limited | Professional & scientific | 2010 |
| Pell Optical Ltd | Wholesale & retail | 2025 |