| OM Wills Limited | Real estate | 2024 |
| Omega Plant Midlands Limited | Professional & scientific | 2024 |
| Omnia Collective Limited | Wholesale & retail | 2017 |
| ON Stream Energy Limited | Professional & scientific | 2017 |
| ON the Brush Limited | Construction | 2018 |
| One Bay House Ltd | Real estate | 2024 |
| One High Performance Coaching Limited | Professional & scientific | 2012 |
| One Horizon Wealth Limited | Extraterritorial | 2025 |
| One to One Care Group Ltd | Health & social care | 2025 |
| One to One Crisis Intervention Limited | Health & social care | 1998 |
| Onebuild (South West) Limited | Construction | 2017 |
| Onpoint Financial Limited | Financial services | 2016 |
| Onspot Surveys Ltd | Administrative & support | 2001 |
| Opcwtch CIC | Public administration | 2026 |
| Open Door Interiors Limited | Other services | 2011 |
| Optiflow Limited | Professional & scientific | 1999 |
| Optima Insights Limited | Other services | 2015 |
| Optimal First AID Limited | Education | 2021 |
| Opus Engineering Consultants Limited | Professional & scientific | 2013 |
| Orbital Fire Safety Ltd | Construction | 2019 |
| Orbital Surveys Ltd | Professional & scientific | 2017 |
| Orchard Garage Lustleigh Ltd | Wholesale & retail | 2025 |
| Orchid Fluid Services Ltd | Professional & scientific | 2021 |
| Orestone Fire Protection Group Ltd | Financial services | 2024 |
| Orestone Fire Protection Ltd | Construction | 2016 |
| Orestone Group Ltd | Financial services | 2023 |
| Orestone Property Group Ltd | Real estate | 2023 |
| Orom Futures Limited | Real estate | 2025 |
| Orthopaedic Horizons Limited | Health & social care | 2017 |
| OS Financial Contractors Limited | Financial services | 2020 |
| Ostrisnack Ltd | Hospitality | 2025 |
| Ostrota Limited | Professional & scientific | 2016 |
| Otter Trades & Management Services Limited | Construction | 1997 |
| OUR Culture Ltd | Information & communication | 2022 |
| OUR Road Limited | Real estate | 2025 |
| Outdoor Carpets Limited | Construction | 2012 |
| Outdoor Innovations SW Ltd | Administrative & support | 2025 |
| Outdoor Play Devon Limited | Manufacturing | 2016 |
| Outerbridge Limited | Information & communication | 2010 |
| Outposts Marketing Limited | Administrative & support | 2016 |
| Outside-Devon Limited | Hospitality | 2021 |
| Overgang Limited | Professional & scientific | 2021 |
| OW Exhibitions Limited | Administrative & support | 2016 |
| Ozone PHG Ltd | Construction | 2025 |
| P & P Aviation Training Ltd | Education | 2018 |
| P C Builders Ltd | Construction | 2008 |
| P Fitness Ltd | Arts & recreation | 2020 |
| P J Lavis (Qmtc) Limited | Professional & scientific | 2003 |
| P T Symes Ltd | Professional & scientific | 2002 |
| P&Db Ltd | Hospitality | 2019 |
| P&L Valentine Ltd | Health & social care | 2022 |
| P&O Metals Limited | Construction | 2015 |
| P&Re Limited | Construction | 2018 |
| P.P.D. (Hotels) Limited | Hospitality | 1973 |
| Packmark Limited | | 1983 |
| Padders Pest Control Ltd | Professional & scientific | 2026 |
| Paddlup Limited | Wholesale & retail | 2019 |
| Padel Groundworks Ltd | Construction | 2024 |
| PAG Fleet and Plant Consultancy Limited | Professional & scientific | 2023 |
| Page Family Homes Ltd | Real estate | 2019 |
| Palaeogames Ltd | Information & communication | 2022 |
| Palmer Construction Brickworks Ltd | Construction | 2021 |
| Palmer Property Solutions Limited | Real estate | 2019 |
| Palmers Bathrooms & Kitchens Ltd | Construction | 2026 |
| Palmers Properties Ltd | Real estate | 2015 |
| Paluma Holdings Limited | Real estate | 2022 |
| Panther Vision Limited | Information & communication | 2008 |
| Paradigm Engineering Design Limited | Manufacturing | 2001 |
| Paragon Care Limited | Hospitality | 2007 |
| Paragon Nationwide Ltd | Construction | 2025 |
| Paramount 21 Limited | Manufacturing | 1988 |
| Park Hill House Residents Association Limited | Hospitality | 1996 |
| Park Home Eco Ltd | Other services | 2012 |
| Parke Interiors Limited | Professional & scientific | 2008 |
| Parker Adams Ltd | Construction | 2019 |
| Parkerwren Group Ltd | Financial services | 2025 |
| Parkhouse Ecology Ltd | Professional & scientific | 2022 |
| Parklink (SW) Ltd | Administrative & support | 2021 |
| Parkway Court Management Company Limited | Real estate | 1991 |
| Part Q Ltd | Real estate | 2026 |
| Participate Arts CIC | Arts & recreation | 2013 |
| Partington Art and Print Limited | Professional & scientific | 2006 |
| Partner of the Future Limited | Extraterritorial | 2025 |
| Partridge Cycles Limited | Administrative & support | 2011 |
| Partridge Group Holdings Limited | Financial services | 2020 |
| Partycubed Limited | Information & communication | 2016 |
| Pass Maths Together Ltd | Education | 2026 |
| Passion for PIE Limited | Hospitality | 2017 |
| Passioni DI Romagna Ltd | Hospitality | 2017 |
| Pastaking (UK) Limited | Manufacturing | 1994 |
| Path and Patio Limited | Wholesale & retail | 2025 |
| Pathfinder Park Homes Holdings Limited | Other services | 2016 |
| Patterson Law Limited | Professional & scientific | 2010 |
| Paulspeaks Ltd | Wholesale & retail | 2025 |
| Pavey & Sons Limited | Real estate | 2016 |
| PAX IT Ltd | Information & communication | 2013 |
| PB Chadwick Holdings Ltd | Real estate | 2023 |
| PB Plumbing and Heating Services SW Limited | Construction | 2023 |
| PB Trees and Landscapes Limited | Agriculture & fishing | 2026 |
| PC Legal Tech Ltd | Information & communication | 2024 |