| Orthopaedic Consultants Ltd | Health & social care | 2025 |
| Ortum Store Limited | Wholesale & retail | 2025 |
| OS Suits Limited | Wholesale & retail | 2016 |
| Osbro Ltd | Wholesale & retail | 2020 |
| Oscar Conveyancing Limited | Professional & scientific | 2026 |
| Oscar Holding Group Limited | Professional & scientific | 2026 |
| Oscar Lifestyle Ltd | Health & social care | 2024 |
| Oscar Property Investments Limited | Real estate | 2021 |
| Oscis Ltd | Wholesale & retail | 2024 |
| Oshana Hudds Ltd | Hospitality | 2025 |
| Osmen Limited | Hospitality | 2021 |
| Osmium Properties Limited | Real estate | 2022 |
| Osora Ltd | Information & communication | 2025 |
| Osteltec Ltd | Extraterritorial | 2009 |
| Osteoneks Ltd | Manufacturing | 2024 |
| Otasbeta Company Ltd | Administrative & support | 2017 |
| Otec Hearing Technology Limited | Health & social care | 2016 |
| Otium Plan Ltd | Real estate | 2024 |
| OTS4U Limited | Health & social care | 2022 |
| Oudpotion Ltd | Manufacturing | 2026 |
| OUR Creative Connection Ltd | Professional & scientific | 2021 |
| OUR Cultural Heart Ltd | Information & communication | 2024 |
| OUR Sound Ltd | Arts & recreation | 2018 |
| OUR Way Hair & Beauty Ltd | Other services | 2018 |
| Oustar Ltd | Wholesale & retail | 2023 |
| OUT There IS Solutions Limited | Information & communication | 2011 |
| Outback Solutions Limited | Transport & logistics | 2007 |
| Outdoor Lighting Limited | Wholesale & retail | 1972 |
| Outdoor Living Limited | Wholesale & retail | 2004 |
| Outfixly Ltd | Wholesale & retail | 2025 |
| Outlane Cricket Club Ltd | Arts & recreation | 2020 |
| Outlane Fish Shop Limited | Wholesale & retail | 2012 |
| Outlane OUT of School Club Ltd | Health & social care | 2015 |
| Outlane Private Hire Ltd | Transport & logistics | 2021 |
| Outline Limited | Construction | 2023 |
| Outworn Ltd | Wholesale & retail | 2024 |
| Overpaidtax Limited | Professional & scientific | 2009 |
| Overseas Consultants Limited | Professional & scientific | 2021 |
| Overstood Limited | Hospitality | 2015 |
| Owaimer Ltd | Wholesale & retail | 2020 |
| Owen Care and Support Limited | Health & social care | 2011 |
| Owen James Events Limited | Administrative & support | 2005 |
| Owen James Group Ltd | Financial services | 2021 |
| Owen Scott Hire Limited | Wholesale & retail | 2014 |
| Owen Scott Mayfair Ltd | Wholesale & retail | 2025 |
| Owen-Wood Property Investments Limited | Real estate | 2019 |
| OWL Cottage (Wimborne) Limited | Real estate | 2026 |
| OWL Electrical & Security Limited | Construction | 2007 |
| Ox-An Limited | | 1991 |
| Oxalis Logistics UK Limited | Transport & logistics | 1974 |
| Oxdx Ltd | Extraterritorial | 2022 |
| Oxera Repair Products Limited | Manufacturing | 2010 |
| Oxford Group Intl Ltd | Administrative & support | 2019 |
| Oxley Investors Limited | Other services | 2017 |
| Oxtoby Transport Ltd | Transport & logistics | 2011 |
| Oxyair Plus Ltd | Wholesale & retail | 2024 |
| Ozone Property Holdings Limited | Real estate | 2022 |
| OZU Cars Ltd | Wholesale & retail | 2023 |
| P & a Whitehead Limited | Transport & logistics | 2010 |
| P & C Carpentry Ltd | Construction | 2015 |
| P & P Property (Yorkshire) Limited | Construction | 2015 |
| P & R Heating (Yorkshire) Limited | Construction | 2011 |
| P & S Mcgowan (Builders) Limited | Construction | 2003 |
| P and J Futures Limited | Real estate | 2018 |
| P and W Car Hire Ltd | Administrative & support | 2016 |
| P B Select Limited | Administrative & support | 2018 |
| P Colley Limited | Construction | 2023 |
| P England and Co Limited | Professional & scientific | 2021 |
| P Haigh Developments Limited | Construction | 2017 |
| P M Hirst Electrical Limited | Construction | 2014 |
| P M J Limited | Construction | 2006 |
| P R Kaye Electrics Ltd | Construction | 2011 |
| P Sidhu Building Services Ltd | Construction | 2024 |
| P Wood Property Limited | Real estate | 2024 |
| P&F Medics Ltd | Health & social care | 2022 |
| P&Scs Ltd | Professional & scientific | 2026 |
| P&V Solutions Limited | Real estate | 2015 |
| P. & S.L. Sykes Limited | Other services | 1978 |
| P. Brierley Holdings Limited | Financial services | 2021 |
| P.B. Horticultural Limited | Wholesale & retail | 1993 |
| P.L.K Associates Limited | Information & communication | 2014 |
| P.L.P Properties Limited | Real estate | 2023 |
| P.M. Auto Repairs Limited | Wholesale & retail | 2004 |
| P1 Construction Limited | Professional & scientific | 2016 |
| P2F Limited | Administrative & support | 2012 |
| P3PM Ltd | Information & communication | 2012 |
| P4PMND CIC | Other services | 2025 |
| P4RISHHUDD Ltd | Hospitality | 2024 |
| Pabla Global Consulting Limited | Financial services | 2026 |
| Pacific Electrical Ltd | Wholesale & retail | 2014 |
| Pacific Lifestyle Limited | Wholesale & retail | 1982 |
| Pacific Property Asset Limited | Real estate | 2025 |
| Pack Property Solutions Ltd | Construction | 2024 |
| Packaging Elements Limited | Administrative & support | 2014 |
| Packhorse Management Services Ltd | Real estate | 2021 |
| Packnexa Ltd | Wholesale & retail | 2026 |
| Pacman Civil Engineering Ltd | Construction | 2012 |
| Paddock and Longwood Family Practice Limited | Health & social care | 2020 |
| Paddock CB & AC Enterprises Limited | Wholesale & retail | 2011 |
| Paddock Cricket,Bowling and Athletic Club | Arts & recreation | 2011 |