| Ouseburn Wharf Limited | Real estate | 2004 |
| OUT of Chaos Ltd | Administrative & support | 2023 |
| OUT of Harm's Reach Limited | Health & social care | 2002 |
| OUT of Heaven Dance and Fitness Limited | Other services | 2018 |
| OUT of Office Social Limited | Other services | 2026 |
| OUT YOU Want Ltd | Real estate | 2025 |
| Outcheaservices Ltd | Professional & scientific | 2023 |
| Outdoor Care Ltd | Administrative & support | 1999 |
| Outdoor EYE Ltd | Professional & scientific | 2024 |
| Outdoor Merch Limited | Wholesale & retail | 2025 |
| Outdore Limited | Administrative & support | 2020 |
| Outdore Sites Ltd | Administrative & support | 2022 |
| Outer West Group Ltd | Construction | 2022 |
| Outfox Commercial Limited | Administrative & support | 2015 |
| Outline Partners Limited | Professional & scientific | 2003 |
| Outreach Limited | Professional & scientific | 2025 |
| Outside Catering Limited | Hospitality | 1998 |
| Outsourced Business Solutions Limited | Administrative & support | 2015 |
| Outsourcemybooks Limited | Professional & scientific | 2015 |
| Outstanderful Europe LLP | | 2016 |
| OV Inspection Services Ltd | Construction | 2026 |
| Overakiasss Ltd | Information & communication | 2018 |
| Overlay Couture Limited | Manufacturing | 2018 |
| Overthwarts Management Company Limited | Real estate | 2007 |
| Owen Hopkins Ltd | Information & communication | 2021 |
| Owen Humble Property Investments Limited | Real estate | 2002 |
| OWL Contractor Services Ltd | Construction | 2018 |
| Owlets Tuition Limited | Education | 2025 |
| Own by Chloe Ltd | Wholesale & retail | 2017 |
| Own by Chloe Properties Ltd | Real estate | 2020 |
| OWS Radiology Ltd | Health & social care | 2020 |
| Owtsourced Limited | Information & communication | 2026 |
| OX Enterprises Ltd | Hospitality | 2024 |
| OX Music Ltd | Arts & recreation | 2022 |
| Oxbridge Mentors Ltd | Education | 2025 |
| Oxclose Limited | Real estate | 2022 |
| Oxecraft Leisure Limited | Transport & logistics | 2001 |
| Oxford Comma Translation Ltd | Information & communication | 2013 |
| Oxfordcambridgeinternational Ltd | Education | 2026 |
| Oxley Close Residual Limited | Real estate | 2018 |
| Oxley Efficient Group Limited | Construction | 2025 |
| Oxley Mews Management Company Limited | Real estate | 2003 |
| Oxley Plumbing and Heating Limited | Construction | 2025 |
| Oxnam Limited | Professional & scientific | 2020 |
| Oxus Recruitment Ltd | Administrative & support | 2017 |
| OYB Developments Ltd | Manufacturing | 2024 |
| OYE Group Holdings Ltd | Financial services | 2024 |
| Oyin Motor Services Ltd | Wholesale & retail | 2025 |
| Oyster Opera Ltd | Extraterritorial | 2009 |
| OZ Management Ltd | Professional & scientific | 2018 |
| P & a Groundworks Limited | Construction | 2013 |
| P & K (North East) Limited | Wholesale & retail | 2013 |
| P & L Electrical Ltd | Construction | 2006 |
| P & M Curry Limited | Wholesale & retail | 2013 |
| P & N Clifton Holdings Ltd | Financial services | 2016 |
| P & S Gradwell Limited | Public administration | 2003 |
| P & S Medical Education Limited | Education | 2014 |
| P & T Business Limited | Health & social care | 2014 |
| P B Fork Lift Training Limited | Transport & logistics | 2020 |
| P Baxter Ceilings Limited | Construction | 2014 |
| P D Scaffolding Ltd | Construction | 2009 |
| P F 168 Ltd | Hospitality | 2024 |
| P G Bell Properties Limited | Professional & scientific | 2018 |
| P M Westwood Limited | Professional & scientific | 2025 |
| P Phillips Ltd | Information & communication | 2024 |
| P Porter Property Holdings Limited | Real estate | 2021 |
| P Realisations 2024 Limited | Wholesale & retail | 2017 |
| P&D Consultance Ltd | Professional & scientific | 2026 |
| P&R Groundworks Ltd | Construction | 2015 |
| P&S Education Holdings Limited | Health & social care | 2022 |
| P&S Medical Professionals Limited | Health & social care | 2022 |
| P&S Site Services Limited | Construction | 2020 |
| P&T Residential Ltd | Real estate | 2025 |
| P. James Construction Limited | Construction | 1997 |
| P. Madog Offshore Services Ltd | Transport & logistics | 2000 |
| P.A. Jackson Limited | Administrative & support | 2011 |
| P.A.Holmes Ltd | Construction | 2014 |
| P.A.L.S. Packaging & Leisure Solutions Ltd | Wholesale & retail | 2014 |
| P.C.S. Professional Computer Services Limited | Information & communication | 1986 |
| P.D. Parkinson & SON Properties Ltd | Construction | 2003 |
| P.Drummond Ltd | Construction | 2016 |
| P.G.B Transport Ltd | Transport & logistics | 2025 |
| P.M.P Contract Services Limited | Construction | 2017 |
| P.T Joinery & Sash Windows Ltd | Construction | 2024 |
| P1COMPS Ltd | Manufacturing | 2026 |
| P5 Technology Services Ltd | Professional & scientific | 2009 |
| PA Beauty Ltd | Other services | 2025 |
| Pablo Solutions Limited | Information & communication | 2007 |
| Pacific Chem Ltd | Wholesale & retail | 2013 |
| Packaging Works Limited | Manufacturing | 2010 |
| Packham & Bell Ltd | Manufacturing | 2023 |
| Packshack Limited | Transport & logistics | 2021 |
| PAD Refurbishment Ltd | Real estate | 2024 |
| Padaptations Limited | Construction | 2020 |
| Paddlepod Active Community Education Limited | Arts & recreation | 2013 |
| Paddlepod Limited | Arts & recreation | 2021 |
| Padlock PAD Ltd | Education | 2026 |
| Padmartha Insights Ltd | Information & communication | 2026 |
| Pafa Electrical Consulting Ltd | Construction | 2024 |
| Pageline Solutions Accountants Limited | Professional & scientific | 2012 |