| Onkaar Builders Ltd | Construction | 2026 |
| Onkaar Investments Ltd | Real estate | 2023 |
| Only Video Limited | Wholesale & retail | 2002 |
| Oomph Creative LLP | | 2014 |
| Opaltech Renewables Ltd | Construction | 2025 |
| Open Architecture and Technology for Entrances Limited | Construction | 2004 |
| Open Games Studio Ltd | Information & communication | 2026 |
| Open Water Development Ltd. | Professional & scientific | 2008 |
| Opening the Gates Ltd | Administrative & support | 2023 |
| Openspace Group Limited | Other services | 2017 |
| OPSVIEW360 Ltd | Professional & scientific | 2023 |
| Optimum Personal Development Limited | Wholesale & retail | 2019 |
| Oscar Insurance Brokers Ltd | Financial services | 2021 |
| Oscar Investment Holdings Ltd | Financial services | 2023 |
| Oscar SPV Ltd | Professional & scientific | 2023 |
| OUR Planet 360 Ltd | Information & communication | 2017 |
| Ouse Valley Plumbing Limited | Construction | 2014 |
| Ousebank House CIC | Hospitality | 2019 |
| Oyak Ventures Ltd | Real estate | 2023 |
| P & L Woodward Plumbing and Heating Ltd | Construction | 2018 |
| P.M. Strategies Limited | Administrative & support | 2010 |
| P31 Cafe Ltd | Hospitality | 2025 |
| PAB Engineering Consultants Limited | Professional & scientific | 2024 |
| Padre Homes Ltd | Real estate | 2017 |
| Pagg's Court Management Ltd | Administrative & support | 2013 |
| PAL (Tollgate) Ltd | Construction | 2015 |
| PAL Austin Mews Limited | Real estate | 2017 |
| Palebrick Studio Ltd | Professional & scientific | 2026 |
| Panidea Limited | Administrative & support | 2021 |
| Parentassess Ltd | Health & social care | 2004 |
| Parentassess Trustee Limited | Financial services | 2024 |
| Park House Gallery Limited | Arts & recreation | 2019 |
| Patey-Smith Property Ltd | Real estate | 2016 |
| Patronus Management Limited | Professional & scientific | 2014 |
| Paul Bryan Limited | Professional & scientific | 2005 |
| Paul Forrest Limited | Professional & scientific | 2012 |
| Paws and Lattes Ltd | Wholesale & retail | 2025 |
| Paws in Motion Canine Rehab Ltd | Professional & scientific | 2026 |
| Paysave Ltd | Professional & scientific | 2024 |
| PBB EPI & Analytics Ltd | Professional & scientific | 2024 |
| PC Construction NW Ltd | Construction | 2018 |
| PDC Consultants (UK) Ltd | Information & communication | 2010 |
| Peace of Mind Consultations Ltd | Real estate | 2015 |
| Peachy Health Limited | Health & social care | 2012 |
| Pear Tree PR & Communications Limited | Professional & scientific | 2025 |
| PEB Engineering Solutions Limited | Professional & scientific | 2016 |
| People Tower Ltd | Administrative & support | 2017 |
| Perfect Property Sourcing Limited | Real estate | 2018 |
| Pet Care Solutions Ltd | Other services | 2020 |
| Petar Dimov Ltd | Transport & logistics | 2014 |
| Peter Knott Ltd | Administrative & support | 2007 |
| Petrocad Ltd | Information & communication | 2017 |
| Petrogas Holdings UK Limited | Financial services | 2018 |
| Pettingrew 1967 Limited | Extraterritorial | 2013 |
| Pggl Ltd | Transport & logistics | 2021 |
| PGU Engineering Services Ltd | Professional & scientific | 2014 |
| Pguk Trsa I Limited | Extraterritorial | 2021 |
| Pguk Trsa II Limited | Wholesale & retail | 2021 |
| Pguk Trsa III Limited | Wholesale & retail | 2021 |
| Phil Parker Group Limited | Financial services | 2009 |
| Phil Parker Training Limited | Health & social care | 2003 |
| Philton Property Management Limited | Households | 1993 |
| Phoenix Scale Publications LLP | | 2021 |
| Physix Sports Medicine Limited | Extraterritorial | 2010 |
| Pinnacle City Suites Ltd | Real estate | 2024 |
| Pipetek Limited | Professional & scientific | 2015 |
| Pippa Matthews Coaching Limited | Other services | 2019 |
| PJM Composites Ltd | Manufacturing | 2005 |
| PK Building Renovations Limited | Construction | 2017 |
| PK ENT Services Ltd | Health & social care | 2024 |
| Plan My Property Limited | Professional & scientific | 2015 |
| Planet Holdco Limited | Financial services | 2024 |
| Plenipotentiary Technology Limited | Information & communication | 2004 |
| Pnlj Limited | Administrative & support | 2022 |
| Podraffi Limited | Information & communication | 2016 |
| Pohutukawa Coffee Limited | Hospitality | 2018 |
| Polaris Plastics Limited | Extraterritorial | 1976 |
| Portable Annexes Limited | Construction | 2022 |
| Portfields MK Limited | Administrative & support | 2020 |
| Portfolio Management Estates Limited | Real estate | 2011 |
| Powell Associates Limited | Construction | 2006 |
| Power Pro Marketing Ltd | Energy | 2025 |
| Powered by Pollen Ltd | Administrative & support | 2023 |
| Praesidium Solutions Limited | Administrative & support | 2014 |
| Prestige Home Windows and Doors Ltd | Construction | 2026 |
| Prestige Security Consulting Limited | Professional & scientific | 2010 |
| Prigital Ltd | Information & communication | 2019 |
| Prime Electrical Installations Limited | Construction | 2022 |
| Prime Letts Limited | Administrative & support | 2017 |
| Prime Letts MK Limited | Administrative & support | 2019 |
| Prime Recruitment BBH Limited | Administrative & support | 2017 |
| Prime Rentals and Property Management Ltd | Real estate | 2016 |
| Primus Pet Ltd | Manufacturing | 2021 |
| Primus Project Management Limited | Professional & scientific | 2012 |
| Priority Cleaning Contractors (Milton Keynes) Limited | Administrative & support | 1976 |
| Priory END Estates Ltd | Real estate | 2025 |
| Prism Shift Media Limited | Professional & scientific | 2025 |
| Pro Trade Connect Ltd | Information & communication | 2025 |
| Pro Windscreens Limited | Wholesale & retail | 2006 |
| Proact Cleaning Ltd | Extraterritorial | 2018 |