| Orco Limited | Administrative & support | 1990 |
| Organic Connections Limited | Wholesale & retail | 1996 |
| Orions Belt Contracts Limited | Administrative & support | 2004 |
| Oryx Black Edition Limited | Administrative & support | 2022 |
| Osom Apparel Ltd | Administrative & support | 2020 |
| Ossy IT Technology Ltd | Wholesale & retail | 2018 |
| Osteopathic Therapy Limited | Health & social care | 2004 |
| Otodynamics Audiological Equipment Services Ltd. | Professional & scientific | 1995 |
| Otodynamics Limited | Manufacturing | 1988 |
| Ototek Limited | Professional & scientific | 1994 |
| OU Laite Electronic Commerce Co., Ltd | Wholesale & retail | 2021 |
| Outdoor Products Investment Company Limited | Professional & scientific | 1988 |
| Outdoor Trading Post Limited | Professional & scientific | 1994 |
| Outofmyhat.Com Limited | Information & communication | 2001 |
| Own Homes Lettings Limited | Real estate | 2006 |
| Oyster Studios Limited | Professional & scientific | 1998 |
| P & P Services (Ware) Limited | Construction | 1997 |
| P & S Asset Finance Limited | Financial services | 1996 |
| P a Environmental Services Limited | Administrative & support | 2005 |
| P C K Accounting Ltd | Professional & scientific | 2002 |
| P M Painters & Decorators Limited | Construction | 2007 |
| P Smith Network Communications Limited | Information & communication | 1999 |
| P.A. Toms Limited | Arts & recreation | 1973 |
| P.B.I. Design Consultants Limited | | 1981 |
| P.C. Gill & Sons (Property) Limited | Wholesale & retail | 1971 |
| P.D.S. (Kimprint) Limited | Manufacturing | 2002 |
| P4L Limited | Real estate | 2001 |
| PA Building Ltd | Construction | 2017 |
| Pabulum Media Limited | Extraterritorial | 2001 |
| Page Lane Developments Limited | Construction | 1985 |
| Pages Publishing Limited | Information & communication | 2008 |
| Pages Stud Farm Limited | Agriculture & fishing | 2003 |
| Painter & Ellis Limited | Real estate | 2024 |
| Pakex (UK) PLC | Administrative & support | 1995 |
| Palace Court Management (Letchworth) Limited | Households | 1986 |
| Parcels Worldwide Ltd | Transport & logistics | 2011 |
| Paris & Co UK Limited | Professional & scientific | 2002 |
| Parking Investments and Management Ltd | Transport & logistics | 2025 |
| Parking Mind Ltd | Information & communication | 2026 |
| Pateman Taxis Limited | Transport & logistics | 2003 |
| Pathcourt Limited | Information & communication | 2004 |
| Pathrose Limited | Information & communication | 2004 |
| Pawbloomresin Ltd | Wholesale & retail | 2025 |
| Paypoint Retail Solutions Limited | Administrative & support | 2002 |
| PC Consultancy Limited | Professional & scientific | 2012 |
| PC Solutions & Support Limited | Information & communication | 1998 |
| Pearson Taylor Knight Limited | Financial services | 1998 |
| Peckett & Sons Limited | Manufacturing | 1995 |
| Pecks Hill Nursery Limited | Agriculture & fishing | 2003 |
| Peggram Contracts Limited | Construction | 2000 |
| Pembroke and Trinity Management Limited | Real estate | 2007 |
| Pendley Limited | Construction | 2002 |
| Penknife Design Limited | Professional & scientific | 2002 |
| Penman Sedgwick LLP | | 2007 |
| Pepper Publications Limited | Manufacturing | 2004 |
| Pepperbox Limited | Professional & scientific | 2006 |
| Peppertree Broadcast Ltd. | Information & communication | 1996 |
| Peregrine Retail Limited | Wholesale & retail | 1997 |
| Perimed U.K. Limited | Wholesale & retail | 1985 |
| Peter Hartnell Trading Limited | Manufacturing | 2026 |
| Peter Klinger Limited | | 1963 |
| Peter Rennison Public Relations Limited | Administrative & support | 2001 |
| Peter Trehy Limited | Construction | 2003 |
| Peters Surgical Limited | Extraterritorial | 2005 |
| Petflareresin Ltd | Wholesale & retail | 2025 |
| Petite Star Baby Products Limited | Wholesale & retail | 2002 |
| PH GAS Ltd | Construction | 2017 |
| Pharmacists Professional Indemnity Limited | Financial services | 2002 |
| Phase Electrical Services Limited | Construction | 2005 |
| Phase One Properties Limited | Real estate | 1993 |
| Phlush Ltd | Construction | 2022 |
| Phoenix Plumbing & Bathrooms Ltd | Households | 2026 |
| Photosound Vantage Limited | Other services | 1976 |
| Piling and Drilling Supplies and Services Limited | Construction | 2002 |
| Pillar and Post Partnership | | 2005 |
| Pine Hill Media Limited | Other services | 2020 |
| Pine Tops Travel Ltd | Administrative & support | 2021 |
| Pinewhisperhandmade Ltd | Wholesale & retail | 2025 |
| Pink of London Limited | Other services | 2018 |
| Pipedream Investments Limited | Professional & scientific | 2003 |
| Pipers Farm Limited | Agriculture & fishing | 1996 |
| Pips and Skin Ltd | Other services | 2022 |
| Pitchfork SEO Limited | Information & communication | 2024 |
| Pivotal Support Ltd | Professional & scientific | 2004 |
| Pixel POP Ltd | Professional & scientific | 2024 |
| Pixelmotion Limited | Information & communication | 2004 |
| PJ Frameworks Ltd | Construction | 2023 |
| PJB Scaffolding Limited | Construction | 2006 |
| Plains Signs & Blinds and Consultancy Ltd | Other services | 2020 |
| Planned Action Limited | Construction | 1986 |
| Planning Appeal Limited | Professional & scientific | 2020 |
| Platform One Nursery Ltd | Health & social care | 2002 |
| Platinum Shine Ltd | Other services | 2024 |
| Platters Delicatessens & Caterers Limited | Professional & scientific | 1988 |
| Plava Limited | Professional & scientific | 1996 |
| Plusonetestates Ltd | Real estate | 2022 |
| Plyford Limited | Professional & scientific | 1978 |
| PMA I.T. Specialists Limited | Professional & scientific | 2001 |
| PMO Consultancy Limited | Professional & scientific | 2005 |
| POD Decor Ltd | Construction | 2014 |