| Oscar Care Services UK Limited | Health & social care | 2014 |
| OSH Builders Ltd | Construction | 2019 |
| Oshun Partnership Limited | Professional & scientific | 2011 |
| Osiris Engines Ltd | Information & communication | 2025 |
| OSL Rail Limited | Professional & scientific | 2010 |
| Osprey House Residents Association (Trematon Place) Teddington Limited | Real estate | 1991 |
| OSR Associates Limited | Information & communication | 2010 |
| Ossman Consultants Limited | Professional & scientific | 1990 |
| Ossmans Limited | Professional & scientific | 1997 |
| Otis Holdings Limited | Real estate | 2015 |
| Otoko Ltd | Administrative & support | 2013 |
| OUR Day Nursery Ltd | Education | 2019 |
| OUR MAN in UK Ltd | Professional & scientific | 2010 |
| Outsourced Financial Planning Limited | Other services | 2022 |
| Oval Joinery Ltd | Manufacturing | 2008 |
| Over ALL Roofing Ltd | Construction | 2024 |
| Over ARE Ltd | Health & social care | 2014 |
| Over Watch Security & Training Ltd | Other services | 2018 |
| Overcomers Faith Center | Other services | 2007 |
| Overcomers in and Around Africa Ltd | Information & communication | 2025 |
| Overstrand Ltd | Real estate | 2023 |
| Overton Grange School | Education | 2011 |
| OWL Guarding UK Limited | Administrative & support | 2025 |
| OWL Plumbing and Building Ltd | Construction | 2020 |
| Ox-Ray Ltd | Health & social care | 2019 |
| Oxford Intelligent Energy Co. Ltd | Manufacturing | 2021 |
| Oxford Medical Instruments Limited | Wholesale & retail | 2009 |
| Oxhill Aviation Limited | Transport & logistics | 2004 |
| Oxsight Ltd | Professional & scientific | 2016 |
| Oxyderkis Ltd | Information & communication | 2021 |
| Oyster (GB) Solutions Limited | Professional & scientific | 2007 |
| Oyster Music Limited | Information & communication | 1999 |
| OZ Grooming Ltd | Other services | 2017 |
| Oztrading Limited | Wholesale & retail | 2022 |
| P a Murphy Carpentry Ltd | Construction | 2022 |
| P B Wiring Solutions Ltd | Construction | 2011 |
| P D (London) Constructions Limited | Construction | 2013 |
| P D Elkins Drawing Services Limited | Professional & scientific | 2003 |
| P Family Ltd | Real estate | 2022 |
| P House Ltd | Professional & scientific | 2024 |
| P R N News Ltd | Wholesale & retail | 2022 |
| P&I UK Limited | Administrative & support | 2009 |
| P&R Plumbing Bathroom Division Limited | Construction | 2018 |
| P&R Plumbing Services Ltd | Construction | 2022 |
| P&W Event Hire Ltd | Administrative & support | 2015 |
| P-Team Building Solutions Ltd | Construction | 2013 |
| P. Moss Limited | Real estate | 1942 |
| P. Sweets Carpentry Ltd | Manufacturing | 2026 |
| P.A.M Developments (SE) Ltd | Construction | 2007 |
| P.C. Decorations Limited | Construction | 2002 |
| P.D.J Construction Ltd | Construction | 2018 |
| P.H.S. Secretarial Services Limited | Professional & scientific | 1985 |
| P.I.K. Health Distribution Ltd | Construction | 2017 |
| P.P.S.B. Limited | Administrative & support | 2003 |
| P2P Logistics Ltd | Extraterritorial | 2024 |
| Paars Vets Ltd | Professional & scientific | 2025 |
| Pace Construction Services Ltd | Construction | 2007 |
| Pace Housing Ltd | Professional & scientific | 2019 |
| Pacific Maritime Limited | Transport & logistics | 2007 |
| Padeltastic Ltd | Arts & recreation | 2021 |
| Padevli London Limited | Wholesale & retail | 2025 |
| Paek Ltd | Information & communication | 2014 |
| Page & Gleeson Environmental Services Limited | Construction | 2005 |
| Paint and Body Beckenham Outsourcing Ltd | Administrative & support | 2023 |
| Pakka Indian Ltd | Hospitality | 2021 |
| Palace Court Cheam Limited | Households | 2007 |
| Palace Gate Investments Limited | Construction | 1994 |
| Palitek Limited | Information & communication | 2018 |
| Palmer Mortgage and Protection Services Ltd | Financial services | 2025 |
| Palmerston SPV Ltd | Construction | 2023 |
| Palv Ltd | Construction | 2025 |
| Pamela Yates Limited | Health & social care | 2010 |
| Pampered Perfectly Ltd | Arts & recreation | 2026 |
| PAN African Airlines System Ltd | Manufacturing | 2024 |
| PAN Comido Spanish Language School Ltd | Education | 2024 |
| PAN Marketing Limited | Wholesale & retail | 2018 |
| Panacea Law Ltd | Financial services | 2016 |
| Panache Experts UK Ltd | Information & communication | 2018 |
| Panda Wholefoods Limited | Wholesale & retail | 2024 |
| Pandora 7 Ltd | Financial services | 2025 |
| Panel Media Limited | Information & communication | 2021 |
| Panev Ltd | Transport & logistics | 2019 |
| Pangloss AI Ltd | Information & communication | 2022 |
| Panmmas Ltd | Wholesale & retail | 2016 |
| Panmmas Properties Ltd | Real estate | 2024 |
| Panmuir Design Limited | Construction | 2009 |
| Papajova Safetycheck Ltd | Public administration | 2024 |
| Papaya London Limited | Professional & scientific | 2025 |
| Paradise Realty Limited | Real estate | 2024 |
| Paragon Decorators Ltd | Administrative & support | 2017 |
| Paragon Design Construction Limited | Construction | 2012 |
| Paragon Property Holdings Ltd | Administrative & support | 2016 |
| Parametric Concepts Ltd | Administrative & support | 2011 |
| Paramis Consulting Limited | Information & communication | 2016 |
| Paran Estates Limited | Real estate | 2025 |
| Paras Pharma Ltd | Wholesale & retail | 2024 |
| Parcel Logic Limited | Transport & logistics | 2023 |
| Parched Digital Ltd | Professional & scientific | 2025 |
| Parina Ltd | Wholesale & retail | 2025 |
| Parisa London Ltd | Wholesale & retail | 2022 |