| One Gym Fitness Ltd | Arts & recreation | 2025 |
| One Stop Takeaway (Wellingborough) Ltd | Hospitality | 2019 |
| One%Better Limited | Information & communication | 2025 |
| One-Ip.Net Limited | Information & communication | 2000 |
| Oneix Ltd | Wholesale & retail | 2020 |
| Ones Way Logistics Limited | Transport & logistics | 2025 |
| Onesolve Consulting Limited | Extraterritorial | 2016 |
| Onkx Ltd | Real estate | 2021 |
| Online Gaming Media Limited | Extraterritorial | 2018 |
| Only Rafael Ltd | Transport & logistics | 2019 |
| Only Solar Ltd | Construction | 2022 |
| Onyekason Services Ltd | Wholesale & retail | 2015 |
| Oort Studios Ltd | Information & communication | 2026 |
| Open House Kettering Limited | Real estate | 2024 |
| Opium Restaurants Ltd | Real estate | 2025 |
| Opportunity Forge Limited | Professional & scientific | 2017 |
| Optiluxé Ltd | Wholesale & retail | 2025 |
| Options Services International Ltd | Administrative & support | 1999 |
| Options Services UK Ltd | Administrative & support | 1999 |
| Optrans Ltd | Transport & logistics | 2017 |
| Optus MSS Ltd | Administrative & support | 2017 |
| Opulent Homes Group Ltd | Real estate | 2025 |
| Opus Civil Engineering Ltd | Construction | 2014 |
| Orange Bear Software Ltd | Information & communication | 2023 |
| Orange Mint Ltd | Real estate | 2020 |
| Oraros Ltd | Information & communication | 2026 |
| Orbitalvsat Ltd | Wholesale & retail | 2026 |
| Orbus Europe Limited | Extraterritorial | 2001 |
| Orchard Design House Limited | Arts & recreation | 2019 |
| Orchard Street (Fleckney) Management Company Limited | Real estate | 2010 |
| ORG Limited | Health & social care | 2018 |
| Orient House Holdings Limited | Professional & scientific | 2019 |
| Origin Group Solutions Ltd | Construction | 2022 |
| Orion Office Park Management Company Limited | Real estate | 2006 |
| Orosan Ltd | Health & social care | 2018 |
| Oscar G Limited Ltd | Transport & logistics | 2024 |
| Osentra Ltd | Information & communication | 2026 |
| Osmanthus Care Ltd | Health & social care | 2021 |
| Osprey Sentinel Limited | Financial services | 2026 |
| OTE Solutions Ltd | Professional & scientific | 2023 |
| OTI Logistics Ltd | Transport & logistics | 2017 |
| Otia Properties Ltd | Real estate | 2023 |
| Otisoft Limited | Information & communication | 2025 |
| OUT of HRS Limited | Professional & scientific | 2016 |
| Outsource Solutions Limited | Professional & scientific | 2001 |
| Outstanding Solutions Ltd | Administrative & support | 2014 |
| Outtuu Ltd | Real estate | 2021 |
| OVB Limited | Construction | 2017 |
| OVR Solutions Ltd | Information & communication | 2024 |
| OVT Business Solutions Limited | Professional & scientific | 2009 |
| Owen ME Holdings Limited | Financial services | 2026 |
| Owen Refrigeration Limited | Administrative & support | 2001 |
| Oxford Court Limited | Real estate | 2018 |
| Oxford Events & Catering Ltd | Hospitality | 2024 |
| Oxford Premier Cars Services Limited | Transport & logistics | 2021 |
| Oxford Sightcare (2018) Limited | Health & social care | 2018 |
| Ozen&Sakarya Ltd | Real estate | 2025 |
| P & M Pizza Takeaway Limited | Hospitality | 2018 |
| P C Civil Engineering Limited | Construction | 2022 |
| P Johnston Construction Ltd | Construction | 2015 |
| P Jones Collections Ltd | Administrative & support | 2012 |
| P Larkin Logistics Limited | Transport & logistics | 2015 |
| P R Farman Limited | Construction | 2004 |
| P Thurlow Limited | Transport & logistics | 2015 |
| P&S Solutions Ltd | Transport & logistics | 2025 |
| P.G Drivers Ltd | Transport & logistics | 2017 |
| P.J. Racing Ltd | Arts & recreation | 2003 |
| P.O. Apartments Ltd | Real estate | 2014 |
| P.T.A. UK Limited | Manufacturing | 2003 |
| P2P Delivery Ltd | Transport & logistics | 2022 |
| P3 Group Europe Limited | Professional & scientific | 1970 |
| Pacificleisure Ltd | Arts & recreation | 2026 |
| PAD Builders (Northants) Ltd | Construction | 2012 |
| PAD Print UK Limited | Wholesale & retail | 2003 |
| Padel Power (Holdings) Limited | Financial services | 2026 |
| Pado Lambrino Ltd | Transport & logistics | 2022 |
| Pakha Baby Ltd | Wholesale & retail | 2021 |
| Palace Leisure Ltd | Hospitality | 2023 |
| Pallite Group Ltd | Manufacturing | 2008 |
| Pallite Limited | Professional & scientific | 2013 |
| Palmerston House Ltd | Households | 2010 |
| Panath Global Support Services Ltd | Transport & logistics | 2025 |
| Pannonia Auxiliary Support Company Ltd | Transport & logistics | 2025 |
| Pantry Pubco Ltd | Hospitality | 2019 |
| Paper Industry Charitable Trust | Other services | 2006 |
| Paradaise Ltd | Hospitality | 2021 |
| Paris Miah Ltd | Real estate | 2021 |
| Park Estates Wellingborough Limited | Real estate | 2020 |
| Park Road Property Developments Ltd | Construction | 2014 |
| Parker & SON Investment Group Ltd | Financial services | 2025 |
| Parker & SON Transport Ltd | Transport & logistics | 2014 |
| Parker ADS Ltd | Professional & scientific | 2026 |
| Parker Equipment Hire Ltd | Administrative & support | 2014 |
| Parker Transport Holdings Ltd | Financial services | 2014 |
| Parker's Finance Solutions Ltd | Professional & scientific | 2017 |
| Parkin Brickwork Limited | Construction | 2018 |
| Parmar Estate Holdings Ltd | Real estate | 2019 |
| Partilandkids Ltd | Arts & recreation | 2026 |
| Partnerfast! Ltd | Information & communication | 2022 |
| Partridge Support Services Limited | Health & social care | 2022 |