| Other Side Fried Events Ltd | Hospitality | 2019 |
| Otocyon Limited | Professional & scientific | 2006 |
| Otrade Consultants Limited | Information & communication | 2013 |
| Ottoman Gems Ltd | Manufacturing | 2022 |
| Ottoman Shield Ltd | Administrative & support | 2025 |
| OUD and Musk Ltd | Wholesale & retail | 2020 |
| OUD Merchant Limited | Wholesale & retail | 2023 |
| Oudacity Ltd | Wholesale & retail | 2023 |
| Oudh AL Anfar UK Ltd | Wholesale & retail | 2020 |
| Oudwaleperfumes Ltd | Manufacturing | 2025 |
| Ouest Deluxe Rentals Ltd | Real estate | 2022 |
| OUR AID | Hospitality | 2018 |
| OUR Property Investment Ltd | Real estate | 2026 |
| Ourwellbeing Ltd | Health & social care | 2022 |
| Oussama Enterprises Ltd | Other services | 2018 |
| OUT and OUT Management Ltd | Construction | 2024 |
| Outback Scaffolding Limited | Construction | 1998 |
| Outcome Baits Ltd | Wholesale & retail | 2024 |
| Outfit Direct Limited | Wholesale & retail | 2022 |
| Outlet (London) Limited | Wholesale & retail | 2003 |
| Outlet Centre Ltd | Wholesale & retail | 2019 |
| Outline Consulting Limited | Professional & scientific | 2024 |
| Outlook Travel Ltd | Administrative & support | 2025 |
| Outreach Management Services Ltd | Professional & scientific | 2022 |
| Outsourcing and Marketing Ltd | Administrative & support | 2017 |
| OV Designs Ltd | Wholesale & retail | 2014 |
| Oval Security Group Limited | Administrative & support | 2025 |
| Ovalade Limited | | 1992 |
| Ovamile Limited | Administrative & support | 2010 |
| Ovan Property Limited | Real estate | 2024 |
| Ovata Investments Limited | Real estate | 2020 |
| Ovdu Limited | Construction | 2022 |
| OVE Investments Ltd | Real estate | 2022 |
| Over 50'S Black MEN Forum CIC | Other services | 2021 |
| Overseas Friends of Anjuman, UK | Education | 2023 |
| Overstated Limited | Wholesale & retail | 2023 |
| Overzest Community Services Ltd | Health & social care | 2020 |
| Overzest Ltd | Health & social care | 2007 |
| OVI Creativ Solutions Ltd | Construction | 2025 |
| OVI25 Construction Limited | Construction | 2025 |
| Ovid Traders Ltd | Hospitality | 2024 |
| Ovisstyle Ltd | Arts & recreation | 2025 |
| OW Careers Europe Ltd | Administrative & support | 2020 |
| Owens Construction Services Ltd | Construction | 2016 |
| Owesome Store Ltd | Wholesale & retail | 2025 |
| Owners Abroad Limited | Real estate | 2004 |
| Ownership Mark Ltd | Wholesale & retail | 2024 |
| Ownprop Limited | Construction | 2020 |
| Owuje Limited | Health & social care | 2025 |
| OX Building Ltd | Construction | 2024 |
| Oxana Management Properties Limited | Real estate | 2025 |
| Oxbridge Academy London Ltd | Education | 2024 |
| Oxbridge Summer Camps Abroad Ltd. | Education | 2007 |
| Oxedent Marketing Ltd | Professional & scientific | 2023 |
| Oxford Breast Clinic Surgery Ltd | Health & social care | 2020 |
| Oxford Business Technology Sciences Limited | Information & communication | 2015 |
| Oxford College of English Language Teaching | Education | 2001 |
| Oxford College of London Ltd | Education | 2025 |
| Oxford Convenience Ltd | Wholesale & retail | 2021 |
| Oxford Day Nursery Ltd | Education | 2012 |
| Oxford Home Study College Limited | Education | 2013 |
| Oxidize Limited | Manufacturing | 2018 |
| Oxiflo Limited | Water & waste | 2015 |
| Oximium Group Limited | Financial services | 2024 |
| Oxstar Ltd | Construction | 2025 |
| Oxted Properties Ltd | Real estate | 2025 |
| Oxward Capital Ltd | Wholesale & retail | 2025 |
| Oxygen Cars Limited | Real estate | 2011 |
| Oxyheal Limited | Health & social care | 2019 |
| Oyais Housings Ltd | Real estate | 2026 |
| Oyelabs Ltd | Information & communication | 2025 |
| OYO Group Ltd | Wholesale & retail | 2019 |
| Oyster Bay Estate Limited | Real estate | 2017 |
| Ozamsel Ltd | Wholesale & retail | 2023 |
| Oziyke Business Services Limited | Public administration | 2017 |
| Ozkan Restaurants Limited | Hospitality | 2018 |
| Ozmax Limited | Hospitality | 2023 |
| Ozon Construction Ltd | Construction | 2021 |
| Ozora Technologies Ltd | Information & communication | 2025 |
| P & a Properties Limited | Financial services | 2016 |
| P & D Associates Ltd | Real estate | 2024 |
| P & E Plasterers Limited | Construction | 2005 |
| P & S Bakers Ltd | Hospitality | 2023 |
| P & S Consultancy Services Ltd | Real estate | 2021 |
| P & S Medical Ltd | Health & social care | 2010 |
| P ARM Security Ltd | Wholesale & retail | 2025 |
| P Cullen & SON Limited | Construction | 2000 |
| P Dreams Properties Limited | Real estate | 2025 |
| P G Brock & SON Limited | Construction | 2005 |
| P H Fabrications Ltd | Construction | 2001 |
| P J Deery Limited | Construction | 1997 |
| P K J Consultants Limited | Health & social care | 2020 |
| P K Maintenance Limited | Construction | 1997 |
| P M C Ilford Ltd | Other services | 2008 |
| P M C South East Ltd | Administrative & support | 2007 |
| P Moore Roofing Limited | Construction | 1998 |
| P O'Brien Builders (London) Ltd | Administrative & support | 2017 |
| P S Sandhu Construction Ltd | Construction | 2023 |
| P Valeting Ltd | Wholesale & retail | 2025 |
| P&I Builders Limited | Construction | 2013 |