| Osborn Projects Consultancy Limited | Professional & scientific | 2011 |
| Osborne House (Cheltenham) Management Company Limited | Households | 2001 |
| Osborne Park Limited | Health & social care | 2019 |
| Osborne Power Engineering & Business Limited | Professional & scientific | 2022 |
| Oscar 123 Holdings Limited | Financial services | 2016 |
| Oscar 123 Ltd | Real estate | 2003 |
| Oscloud Ltd | Professional & scientific | 2024 |
| Oshwell Ltd | Wholesale & retail | 2023 |
| Osirium Limited | Information & communication | 2008 |
| Osirium Technologies Limited | Information & communication | 2015 |
| Osmium Nuclear Services Limited | Professional & scientific | 2025 |
| Osney Capital Directors Nominees Ltd | Professional & scientific | 2025 |
| OSP Consultancy Limited | Professional & scientific | 2017 |
| Ospreydeepclean International Limited | Extraterritorial | 1999 |
| Ospreydeepclean Limited | Wholesale & retail | 1995 |
| Other Agents Consulting Ltd | Professional & scientific | 2022 |
| OTR Properties Limited | Real estate | 2020 |
| Otter Property Group Limited | Professional & scientific | 2023 |
| Oturu Ltd | Information & communication | 2025 |
| OUI Lounge & Kitchen Limited | Hospitality | 2025 |
| OUR Boy’S Bees Ltd | Agriculture & fishing | 2023 |
| OUR JIM (SW) Limited | Agriculture & fishing | 2025 |
| OUR Little Wardrobe Limited | Wholesale & retail | 2024 |
| OUR People Pictures Ltd | Information & communication | 2025 |
| OUR Spot Property Limited | Real estate | 2024 |
| OUT Brushed Limited | Construction | 2024 |
| OUT Serviced Ltd | Hospitality | 2023 |
| OUT Sprayed Ltd | Manufacturing | 2026 |
| Outdoor Escapes Limited | Administrative & support | 2016 |
| Outdoor Living Designs Limited | Wholesale & retail | 2026 |
| Outdoor Swimmer Shop Limited | Wholesale & retail | 2021 |
| Outdoors Lettings Ltd | Real estate | 2024 |
| Outlook Bespoke Limited | Manufacturing | 2013 |
| Outpost Studios Limited | Information & communication | 2017 |
| Outsourceoperations Limited | Extraterritorial | 2010 |
| Outsourcevoice Ltd | Information & communication | 2007 |
| Over Ground Coffee Ltd | Manufacturing | 2025 |
| Over Yonder Cabins Ltd | Hospitality | 2026 |
| Overbrook Kitchens Limited | Wholesale & retail | 2025 |
| Overbury Investments LLP | | 2009 |
| Overdale House (Stinchcombe) Limited | Health & social care | 2008 |
| Overton Bess Limited | Energy | 2022 |
| Overton Court Management Company Limited | Households | 1981 |
| Overton DC Limited | Information & communication | 2025 |
| Overton Grange Storage Limited | Energy | 2025 |
| Overton NG Limited | Financial services | 2022 |
| OVO Assets Limited | Professional & scientific | 2008 |
| OWL Army Ltd | Information & communication | 2022 |
| Owls Software Ltd | Information & communication | 2024 |
| Owners First Racehorse Management Ltd | Arts & recreation | 2026 |
| OX10 Limited | Real estate | 2016 |
| Oxbarn Farm LLP | | 2026 |
| Oxbutts Garage Ltd | Wholesale & retail | 2025 |
| Oxbutts Trading Limited | Wholesale & retail | 2015 |
| Oxford Design and Innovation Limited | Professional & scientific | 2016 |
| Oxford Hearing Centre Limited | Health & social care | 2007 |
| Oxford House Ltd | Information & communication | 2018 |
| Oxford Refrigeration and Air Conditioning Limited | Extraterritorial | 2006 |
| Oxford Refrigeration Limited | Construction | 1960 |
| Oxford Residential Ltd | Real estate | 2020 |
| Oxford Software Ventures Ltd | Information & communication | 2016 |
| Oxford Street Property Fund Limited Partnership | | 2007 |
| Oxford Ventures Group Limited | Financial services | 1987 |
| Oxfordshire Living Developments Holdings Ltd | Construction | 2025 |
| Oxfordshire Living Developments Ltd | Real estate | 2024 |
| Oxfordten Ltd | Administrative & support | 2013 |
| Oxonline Limited | Professional & scientific | 2004 |
| Oxstalls Plumbing and Heating Ltd | Construction | 2025 |
| Ozlec Electrical Contractors Ltd | Construction | 2022 |
| P & J Partner Investments Ltd | Construction | 2024 |
| P & S Decorators (Cheltenham) Limited | Construction | 1994 |
| P C Access Ltd | Information & communication | 1995 |
| P D H Heating & Plumbing Limited | Construction | 2003 |
| P Express Ltd | Construction | 2018 |
| P H I Technology Ltd | Professional & scientific | 2018 |
| P J C Golf Limited | Arts & recreation | 2018 |
| P J Crook Limited | Arts & recreation | 2018 |
| P J Hance Ltd | Construction | 2010 |
| P J Long Builders Limited | Construction | 2021 |
| P W Commercial Company Limited | Wholesale & retail | 1994 |
| P W Properties (Cheltenham) Limited | Real estate | 2008 |
| P&I Restaurants Limited | Hospitality | 2023 |
| P&J Safety (2016) Ltd | Extraterritorial | 1997 |
| P&N Travels Ltd | Transport & logistics | 2026 |
| P&P European Services Limited | Information & communication | 2016 |
| P. & L.T. Smith Limited | Real estate | 1990 |
| P. O'Neill (WHO) Limited | Health & social care | 2011 |
| P. Williams Limited | Information & communication | 1998 |
| P.C.W. Engraving Limited | Manufacturing | 1992 |
| P.E. Duncliffe Limited | Construction | 1999 |
| P.E.P. Developments Limited | Real estate | 1995 |
| P.E.P. Properties Limited | Real estate | 2001 |
| P.G.B. Carpenters Limited | Manufacturing | 2007 |
| P.H.J Flood Limited | Professional & scientific | 2010 |
| P.I.Lates Chelt Ltd | Arts & recreation | 2023 |
| P1 Plastering Superstore Ltd | Extraterritorial | 2018 |
| P1 the Plasterers 1 Stop Shop Ltd | Extraterritorial | 2018 |
| P14 Medical Limited | Manufacturing | 2017 |
| P2 Growth Ltd | Information & communication | 2024 |
| P27 Midco Limited | Other services | 2018 |