| Opulence Digital Marketing Limited | Wholesale & retail | 2024 |
| Oqsc Ltd | Hospitality | 2022 |
| Orange Events & Entertainment Ltd | Hospitality | 2023 |
| Orbis Mobile Technologies Limited | Information & communication | 2010 |
| Orchid Nails Studio Limited | Other services | 2024 |
| Ordinary MAN Media Ltd | Arts & recreation | 2006 |
| Organdie Holdings Limited | Financial services | 2020 |
| Organisational Edge Advisory Limited | Professional & scientific | 2025 |
| Oriental Abundance Ltd | Manufacturing | 2025 |
| Original Milano Ltd | Hospitality | 2021 |
| Orion Moon Ltd | Information & communication | 2026 |
| Orlava Ltd | Hospitality | 2024 |
| Ortho Store Ltd | Administrative & support | 2008 |
| Osca Childcare Ltd | Health & social care | 2003 |
| Oscestop Education Ltd | Education | 2022 |
| Oscie Construction Ltd | Construction | 2024 |
| OSI Maritime Systems (UK) Ltd | Administrative & support | 2014 |
| Osmans Wood Floors Limited | Construction | 2016 |
| Oswita Blessed Care Ltd | Health & social care | 2023 |
| OT Capital Group Ltd | Financial services | 2025 |
| Otautahi Engineering Limited | Professional & scientific | 2014 |
| Other Creative Limited | Information & communication | 1996 |
| Other Creative Management Services Limited | Professional & scientific | 2012 |
| Other Limited | Professional & scientific | 2002 |
| OTS Motor Hub Limited | Wholesale & retail | 2025 |
| Otterhill Professional Services Ltd | Health & social care | 2018 |
| Otus Ltd | Information & communication | 2011 |
| OU Rouge Cars Limited | Professional & scientific | 2022 |
| Ouiwoo Digital Ltd | Wholesale & retail | 2022 |
| Ouiwoo Hair Ltd | Other services | 2025 |
| OUR House Construction Ltd | Construction | 2021 |
| OUR Space Ltd | Construction | 2021 |
| Ouranos Group Ltd | Professional & scientific | 2023 |
| Ourspaceuk Holdings Ltd | Financial services | 2025 |
| OUT OUT Europe Ltd | Transport & logistics | 2023 |
| Outback Conversions Limited | Manufacturing | 2023 |
| Outbound Odyssey-Electrical Ltd | Manufacturing | 2025 |
| Outdoor Fork Ltd | Hospitality | 2025 |
| Outrageous Leisure Ltd | Hospitality | 2019 |
| Outsider Management Ltd | Professional & scientific | 2019 |
| Outsource QS Ltd | Professional & scientific | 2023 |
| Outstanding Outsourcing Limited | Transport & logistics | 2012 |
| Overdrive Vehicle Movements Limited | Transport & logistics | 2019 |
| Overhead Sound Limited | Information & communication | 2002 |
| OX Hire Ltd | Transport & logistics | 2020 |
| Oxford Research & Analysis Ltd | Other services | 2019 |
| Oxford ST Developments Ltd | Construction | 2011 |
| Oxmed Nexus Limited | Professional & scientific | 2024 |
| OZ Radiology Ltd | Health & social care | 2019 |
| O’Saint Properties Limited | Real estate | 2024 |
| P & KG Design Ltd | Professional & scientific | 2017 |
| P & N Carpets & Flooring Ltd | Construction | 2025 |
| P & N Plastering Contractors Limited | Construction | 2015 |
| P F S Civils Limited | Construction | 2019 |
| P George Practice Limited | Health & social care | 2013 |
| P H Groundworks Limited | Construction | 2008 |
| P Hughes Consulting Ltd | Construction | 2025 |
| P J T Sales Limited | Administrative & support | 2009 |
| P K Landscapes Ltd | Construction | 2023 |
| P N a Solutions Limited | Extraterritorial | 2009 |
| P Plumbing & Heating Limited | Construction | 2017 |
| P R C Electrical Services Limited | Construction | 2007 |
| P T R Consultants Limited | Professional & scientific | 2004 |
| P&A Durham Holdings Ltd | Real estate | 2019 |
| P&Jc Seaton Consultancy Ltd | Professional & scientific | 2022 |
| P&L T Ltd | Professional & scientific | 2019 |
| P&P Motorcycles Limited | Wholesale & retail | 2018 |
| P&T Consultancy Services Ltd | Professional & scientific | 2019 |
| P.A.R.K. Butchers Ltd | Wholesale & retail | 2024 |
| P.D & Sons Home Renovations Ltd | Construction | 2018 |
| P.H Scrap Metal Collections Limited | Water & waste | 2021 |
| P.L. Engineering & Management Limited | Administrative & support | 2015 |
| P.R.D Electrical Ltd | Construction | 2015 |
| P.S. Ducting Limited | Construction | 2012 |
| P34 Beauty Limited | Manufacturing | 2025 |
| P3B Limited | Professional & scientific | 2014 |
| P3M Consulting Ltd | Professional & scientific | 2023 |
| P4N Ltd | Construction | 2014 |
| Pabos Enterprise Ltd | Transport & logistics | 2024 |
| PAC Conference & Event Management Ltd | Other services | 2012 |
| PAC Events Limited | Other services | 2018 |
| Packpullswithnoah Ltd | Wholesale & retail | 2025 |
| PAD Rentals and Renovations Ltd | Real estate | 2022 |
| Paddock Ventures Ltd | Arts & recreation | 2026 |
| Padnell Pre-School | Education | 2011 |
| Page Law Ltd | Professional & scientific | 2022 |
| Paige's Fishing Tackle Limited | Wholesale & retail | 1994 |
| Pain Expert Consultancy Limited | Health & social care | 2023 |
| PAL Nivas Limited | Real estate | 2025 |
| Paleo Pets Ltd | Wholesale & retail | 2023 |
| Paleo Ridge Ltd | Manufacturing | 2021 |
| Palewell Investments Limited | Real estate | 2025 |
| Pallas LT Limited | Information & communication | 2026 |
| Palmer (Waterlooville) Limited | Administrative & support | 2008 |
| Palmer Engineering Limited | Administrative & support | 2008 |
| Palmerstons Contracting Services Limited | Administrative & support | 2025 |
| PAM Mundy Associates Limited | Professional & scientific | 2013 |
| Pamoyi Limited | Households | 2019 |
| Pamper Palace Limited | Health & social care | 2018 |
| PAN Caribbean Ltd | Professional & scientific | 2026 |