| Opal Strategic Insights Ltd | Professional & scientific | 2025 |
| Open Fresh Ltd | Administrative & support | 2017 |
| Open Road 93 Ltd | Transport & logistics | 2021 |
| Open to Exit Limited | Administrative & support | 2025 |
| Openjust Limited | Households | 1990 |
| Operamatics Limited | Information & communication | 2015 |
| Opsis Aesthetic Medical Consultants Limited | Professional & scientific | 2006 |
| Optima Corporation Limited | Real estate | 1997 |
| Optima Location Management Ltd | Real estate | 2016 |
| Optimum EX Ltd | Wholesale & retail | 2025 |
| Optio Investment Partners UK Limited | Administrative & support | 2024 |
| Opus Magic Ltd | Wholesale & retail | 2024 |
| Oral Investments Limited | Real estate | 1998 |
| Orange Advisory Ltd | Administrative & support | 2014 |
| Orange Mate Ltd | Wholesale & retail | 2021 |
| Orangearmy Limited | Education | 2025 |
| Orbital Climate Solutions Limited | Energy | 2011 |
| Orbital Commercial Solutions Limited | Energy | 2024 |
| Orbital Residential Solutions Limited | Energy | 2024 |
| Orbital Service Solutions Limited | Construction | 2023 |
| Orchid Training & Consultancy Limited | Professional & scientific | 2017 |
| Ordinaire Limited | Wholesale & retail | 2020 |
| Organic and Mineral Trade Ltd | Wholesale & retail | 2020 |
| Orgiv Limited | Households | 1967 |
| ORI Lifestyle Limited | Other services | 2019 |
| Orient Quartz Stone Ltd | Manufacturing | 2022 |
| Original Motors Ltd | Wholesale & retail | 2021 |
| Orion Consulting Limited | Information & communication | 1998 |
| Orpton Intervention Limited | Health & social care | 2023 |
| Osbiston Electrical Services Limited | Construction | 2014 |
| Osidge Properties Limited | Real estate | 2020 |
| Osint Centre Ltd | Administrative & support | 2011 |
| Osint Corporation Ltd | Administrative & support | 2016 |
| Osprey Metal Finishers Ltd | Manufacturing | 2011 |
| Osteodent Ltd | Health & social care | 2011 |
| Oswald Murdock Ltd | Professional & scientific | 2013 |
| Otello Services Ltd | Administrative & support | 2018 |
| Otravista Limited | Administrative & support | 2008 |
| OUR Creative Department Ltd | Professional & scientific | 2012 |
| OUR Homes Matter Ltd | Construction | 2020 |
| OUT of Money Limited | Arts & recreation | 2011 |
| OUT of OUR Hands Limited | Arts & recreation | 2011 |
| Outrage Events Limited | Arts & recreation | 2005 |
| Outskirtsfilm Limited | Information & communication | 2025 |
| Oval Topco Limited | Administrative & support | 2021 |
| Overnite Bearings Limited | Wholesale & retail | 1985 |
| Oxygen Skin Care - London Ltd | Wholesale & retail | 2019 |
| OZ Cafe Limited | Hospitality | 2009 |
| OZ Catering Limited | Hospitality | 2021 |
| P B & J Properties Ltd | Other services | 2012 |
| P Brignull Services Limited | Construction | 2013 |
| P&L Gevelmontage Limited | Construction | 2011 |
| P&L Transit Limited | Transport & logistics | 2020 |
| P.A.M. Property Investments Limited | Construction | 2007 |
| Pace Journal Limited | Education | 2018 |
| Pace Rental Limited | | 1960 |
| Paco Technologies Ltd | Information & communication | 2026 |
| Pafpan Ltd | Administrative & support | 2018 |
| Page Global Ltd | Manufacturing | 2005 |
| Paikea Limited | Administrative & support | 2003 |
| Palace Promotions Limited | Manufacturing | 2002 |
| Palma Music Ltd | Arts & recreation | 2023 |
| PAN Mobile Ltd | Other services | 2013 |
| Pana Group Ltd | Administrative & support | 2019 |
| Panahi & Company Limited | Financial services | 2025 |
| Panahi Developments Ltd | Real estate | 2025 |
| Panahi Retail Ltd | Hospitality | 2024 |
| Pandasoft Ltd | Wholesale & retail | 2020 |
| Pandu Tech LP | | 2024 |
| Panesko Limited | Health & social care | 2009 |
| Panimu Solutions Limited | Administrative & support | 2015 |
| Pantelli Associates Limited | Administrative & support | 2002 |
| Pantelli Capital Limited | Financial services | 2020 |
| Pantelli Consultants Ltd | Administrative & support | 2013 |
| Pantelli Group Ltd | Financial services | 2021 |
| Pantelli Investments Limited | Real estate | 2006 |
| Panther (Bromley) Limited | Real estate | 1909 |
| Panther (Dover) Limited | Real estate | 1966 |
| Panther (VAT) Properties Limited | Real estate | 1996 |
| Panther AL (VAT) Limited | Real estate | 2009 |
| Panther AL Limited | Real estate | 2009 |
| Panther Gateshead (VAT) Ltd | Real estate | 1899 |
| Panther Hinckley (VAT) Ltd | Real estate | 2017 |
| Panther Investment Properties Limited | Real estate | 1973 |
| Panther Maldon Industrial Ltd | Real estate | 1934 |
| Panther Securities P L C | Real estate | 1934 |
| Panther Shop Investments (Midlands) Limited | Real estate | 1974 |
| Papcomms Ltd | Arts & recreation | 2024 |
| Paper Sourcing Limited | Wholesale & retail | 2006 |
| Papilo Production Management Limited | Other services | 2009 |
| Paradise DIY (London) Ltd | Administrative & support | 2017 |
| Paragon Complete Solutions Limited | Administrative & support | 2017 |
| Paramount Ventures Limited | Wholesale & retail | 1997 |
| Parioka Limited | Administrative & support | 2025 |
| Park and Vale Limited | Real estate | 2025 |
| Park Avenue Livery Limited | Agriculture & fishing | 2017 |
| Park Street Development & Investments Limited | Real estate | 1997 |
| Parkfield View Management Company Limited | Households | 2000 |
| Parkiluu Iucq Ltd | Wholesale & retail | 2025 |
| Parland Properties Limited | Real estate | 2010 |