| Orbis Surveying & Consultancy Group Ltd | Professional & scientific | 2026 |
| Orbital Infrastructure Assets Ltd | Administrative & support | 2014 |
| Orbital Internet Group Limited | Information & communication | 2002 |
| Orbital NET Limited | Information & communication | 1999 |
| Orbital Telecommunications Limited | Information & communication | 2015 |
| Orchard Views Nickle Farm Ltd | Agriculture & fishing | 2016 |
| Orchid Developments (South East) Limited | Construction | 2019 |
| Orcm Ltd | Arts & recreation | 2021 |
| Ordnance Wharf Limited | Construction | 2002 |
| Orgcredible Ltd | Information & communication | 2026 |
| Oriel Property Ltd | Real estate | 2023 |
| Ormalux Group Ltd | Real estate | 2024 |
| Orme Property Limited | Real estate | 2024 |
| Orme Warrior Property Consultants Limited | Real estate | 2016 |
| Ortwin Thyssen Design Ltd | Wholesale & retail | 2011 |
| Oryx Advisors LLP | | 2017 |
| Oryx Advisory Member Ltd | Professional & scientific | 2017 |
| Oryx Aviation Ltd | Administrative & support | 2022 |
| Oscar Lankford Construction Limited | Construction | 2024 |
| Oscar Tango Victor Ltd | Transport & logistics | 2022 |
| Oscorp Capital Limited | Administrative & support | 2017 |
| OSO Adventure LLP | | 2020 |
| OSO Management Limited | Extraterritorial | 2023 |
| Osotimber Ltd | Professional & scientific | 2021 |
| Osprey Charging Network Ltd | Construction | 2013 |
| Ossies (Kent) Ltd | Wholesale & retail | 2019 |
| Ostberg Sinclair & Co. Group Ltd | Financial services | 2026 |
| Ostberg Sinclair & Co. Ltd | Professional & scientific | 2023 |
| Oteric Services Ltd | Construction | 2021 |
| Otties Kent Ltd | Wholesale & retail | 2019 |
| OUR Way Living Ltd | Real estate | 2026 |
| Outrise Limited | Professional & scientific | 2003 |
| Outset (UK) Limited | Professional & scientific | 2007 |
| Outset Group Limited | Professional & scientific | 2019 |
| Outset Limited | Professional & scientific | 2002 |
| Outstand Limited | Manufacturing | 2004 |
| Ovenden Aggregates Ltd | Extraterritorial | 2020 |
| Ovenden Allworks Limited | Construction | 2012 |
| Ovenden Concrete Ltd | Extraterritorial | 2020 |
| Ovenden Crushing & Screening Services Ltd | Extraterritorial | 2020 |
| Ovenden Crushing and Recycling Ltd | Administrative & support | 2018 |
| Ovenden Demolition Ltd | Construction | 2006 |
| Ovenden Drone Services Ltd | Professional & scientific | 2025 |
| Ovenden Earthmoving Co Ltd | Construction | 1985 |
| Ovenden Motorsport Ltd | Arts & recreation | 2011 |
| Ovenden Plant Hire Limited | Construction | 1974 |
| Ovenden Plant Ltd | Extraterritorial | 2020 |
| Overseas Trade and Business Development Ltd | Professional & scientific | 2016 |
| Ovocare Ltd | Other services | 2025 |
| OWD Holdings Limited | Financial services | 2017 |
| OWL Brewery Limited | Professional & scientific | 2015 |
| OWL Investment Homes Limited | Real estate | 2021 |
| Ownview Property Management Limited | Households | 1993 |
| Oxbridge Enterprise Ltd | Real estate | 2019 |
| Oxford Dental Care Limited | Health & social care | 2009 |
| Oxford Risk Limited | Information & communication | 2002 |
| Oyster Consulting (Kent) Limited | Professional & scientific | 2024 |
| Ozkan Trendy Hair Limited | Other services | 2021 |
| Ozlu 27 Ltd | Hospitality | 2019 |
| OZLU2727 Ltd | Hospitality | 2024 |
| O’Reilly Properties Holdco Limited | Administrative & support | 2026 |
| P & G Scaffolding Limited | Construction | 2008 |
| P & J'S Timberfolk Ltd | Construction | 2025 |
| P & N Haulage & Holdings Limited | Hospitality | 2019 |
| P & V Quenby Ltd | Manufacturing | 2012 |
| P and a Training & Consultants Ltd | Other services | 2009 |
| P Isaac Construction Limited | Construction | 2024 |
| P W Needham Limited | Manufacturing | 1997 |
| P&Jj Ltd | Transport & logistics | 2018 |
| P&M Distributors Ltd | Wholesale & retail | 2021 |
| P-E-N-N Holdings Ltd | Arts & recreation | 2024 |
| P.A. Grant Electrical Contractors Limited | Construction | 1994 |
| P.A. Grant Holding Company Limited | Professional & scientific | 2001 |
| P.A. Grant Property Company Limited | Administrative & support | 2001 |
| P.F. Builders and Contractors Ltd | Construction | 2019 |
| P.H. Electrical Services (S.E.) Limited | Construction | 2013 |
| P.N.N Medical Ltd | Health & social care | 2012 |
| P.P. & Sons Limited | Real estate | 2005 |
| P.R.A.C. Ltd | Financial services | 2012 |
| Paak Ventures Ltd | Administrative & support | 2026 |
| PAB International Limited | Financial services | 2020 |
| PAB Languages Centre Limited | Professional & scientific | 2014 |
| Pace Training UK Limited | Education | 2012 |
| Packlab Ltd | Wholesale & retail | 2025 |
| PAD London Ltd | Arts & recreation | 2007 |
| Padel Pairs Ltd | Arts & recreation | 2026 |
| Padstone Recruitment Limited | Administrative & support | 2017 |
| Paed Consultants LLP | | 2013 |
| Page & Co Property Services Ltd | Real estate | 2016 |
| Page Holdings U.K. Ltd | Real estate | 2025 |
| Page Medical Limited | Wholesale & retail | 2020 |
| Pages London Limited | Health & social care | 2019 |
| Paige Estates Limited | Real estate | 2020 |
| Paige Long Ltd | Wholesale & retail | 2025 |
| Pajo Web Ltd | Information & communication | 2026 |
| Paka Consultancy Limited | Professional & scientific | 2017 |
| Pakro Ltd | Wholesale & retail | 2024 |
| Paku Homes Limited | Real estate | 2025 |
| PAL Advisory Ltd | Professional & scientific | 2020 |
| Palm Tree Hospitality Limited | Hospitality | 2026 |