| Oaktree Design & Construction Limited | Construction | 2015 |
| Oakwood Collective Limited | Construction | 2024 |
| Obacim Limited | Hospitality | 2025 |
| OBD HF Ltd | Construction | 2025 |
| Obisense Limited | Information & communication | 2010 |
| Ocala Healthcare Limited | Public administration | 2017 |
| Ocala Recruitment Limited | Administrative & support | 2022 |
| Old Bells (Holdings) Limited | Financial services | 2023 |
| Old Bells Construction & Demolition Limited | Construction | 2018 |
| Old Bells Developments Limited | Construction | 2023 |
| Old Bells Farm Ltd | Agriculture & fishing | 2025 |
| Old Bells Hire Limited | Administrative & support | 2018 |
| Old Bones Pickups Ltd | Manufacturing | 2021 |
| Old Fashioned Bathrooms Limited | Wholesale & retail | 2026 |
| Old Shire Hall Developments Limited | Construction | 2019 |
| Olive Grove Finance Ltd | Professional & scientific | 2014 |
| Oliver Van Service and Repair Centre Ltd | Wholesale & retail | 2025 |
| OLM Ltd | Real estate | 2024 |
| Olympus Education Ltd | Education | 2022 |
| OMB Property Investments (Eastern) LLP | | 2018 |
| OMB Property Investments Ltd | Real estate | 2018 |
| One Summer Media Limited | Information & communication | 2025 |
| Ontrax Groundworks Limited | Construction | 2024 |
| Opal Mercia Ltd | Education | 2022 |
| Open Door Consulting Limited | Health & social care | 2012 |
| Optimus GAS Services Limited | Construction | 2015 |
| Optimyse Limited | Information & communication | 1995 |
| Opulencia Capital Partners Limited | Financial services | 2024 |
| Orange Sky Management Limited | Administrative & support | 2009 |
| Orange Sky Marketing Ltd | Administrative & support | 2011 |
| Orbital Global Group Limited | Information & communication | 2003 |
| Orchard Barn Environmental Education Centre (Obee) Community Interest Company | Agriculture & fishing | 2007 |
| Orchard Garage DMS Limited | Wholesale & retail | 2018 |
| Orchestrated Technology Limited | Information & communication | 2021 |
| Organic Law Ltd | Professional & scientific | 2021 |
| Organisationinbloom Limited | Professional & scientific | 2024 |
| Original Consulting (Europe) Ltd | Professional & scientific | 2019 |
| Orton-Reynolds Limited | Financial services | 2026 |
| Orwell Consult Ltd | Financial services | 2024 |
| Orwell Content Management Limited | Administrative & support | 2013 |
| Osea Concept Ltd | Wholesale & retail | 2023 |
| Osprey Court Management Company Limited | Households | 1983 |
| Otley Homes JV Limited | Construction | 2025 |
| Otley Homes Limited | Construction | 2020 |
| Otley Homes Rentals Limited | Real estate | 2024 |
| Otley Homes SVP Ltd | Construction | 2023 |
| OTM Property Renovations Ltd | Real estate | 2024 |
| Ottmor Property Ltd | Financial services | 2024 |
| Outdoor Perfection Ltd | Construction | 2023 |
| Outdoor Places & Spaces Limited | Manufacturing | 2017 |
| Oversteer Motorsport Limited | Manufacturing | 2013 |
| OW Investments Limited | Real estate | 2019 |
| OWB Developments Ltd | Administrative & support | 2024 |
| O’Donovan Engineering (UK) Limited | Wholesale & retail | 2024 |
| P J Barty Limited | Transport & logistics | 2004 |
| P&J Light Haulage Ltd | Transport & logistics | 2025 |
| P.B Construction (London) Limited | Construction | 2011 |
| PA Welburn Ltd | Professional & scientific | 2018 |
| PAC 2015 Ltd | Administrative & support | 2008 |
| Paddle & Drift Ltd | Arts & recreation | 2020 |
| Pages Farm Holdings Ltd | Real estate | 2024 |
| Pagoda Consulting Limited | Professional & scientific | 2024 |
| Pahus (Public Arts Health & US) Studios Limited | Information & communication | 2021 |
| Pair of Feet Limited | Health & social care | 2012 |
| Palmer's Plumbing & Heating Limited | Construction | 2011 |
| Palmex Limited | Hospitality | 2013 |
| Pamflete Consulting Limited | Professional & scientific | 2022 |
| Pamper and Polish Limited | Other services | 2012 |
| PAPER2PRINT Ltd | Professional & scientific | 2015 |
| Parkside Warehousing & Transport Company Limited | Transport & logistics | 1970 |
| Parrish Hairdressers Limited | Other services | 2013 |
| Passione D'Amore Limited | Hospitality | 2023 |
| Passive Wealth Derby Limited | Real estate | 2025 |
| Patience & Hilliard Investment Group Ltd | Financial services | 2024 |
| Patience & Hilliard Limited | Construction | 2022 |
| Pattenden Holdings Limited | Financial services | 2020 |
| Pattenden Property Investments Limited | Real estate | 2020 |
| Paul Henri Limited | Extraterritorial | 2013 |
| Paul Weston Architect Ltd | Professional & scientific | 2011 |
| Pause at Pilgrims Ltd | Arts & recreation | 2026 |
| PDI Innovation Limited | Professional & scientific | 2005 |
| Pe&P Ltd | Construction | 2021 |
| PEA and Elle Ltd | Professional & scientific | 2017 |
| Peachtree Design Limited | Information & communication | 1994 |
| Peak Automatic Gates & Fencing Limited | Construction | 2020 |
| Peggs Joinery Limited | Construction | 2012 |
| PEM Electrical & Maintenance Limited | Construction | 2024 |
| PEM Property Investments Limited | Real estate | 2021 |
| Penn and Company (Suffolk) Limited | Professional & scientific | 2008 |
| Penneys Franchise Limited | Other services | 2013 |
| Penneys Hair Group Limited | Financial services | 2013 |
| Penny Parks Training Ltd | Education | 2004 |
| Peppits Accountancy Limited | Professional & scientific | 2019 |
| Perfect Perennials Limited | Agriculture & fishing | 2004 |
| Perwood Construction Limited | Construction | 2026 |
| Perwood Property Ltd | Construction | 2024 |
| Peter Haines Compliance Consultancy Limited | Professional & scientific | 2006 |
| Petite Pancakes Limited | Hospitality | 2026 |
| PGC Limited | Professional & scientific | 2025 |
| Phantom Events Ltd | Professional & scientific | 2020 |