| Nashoban Limited | Information & communication | 2002 |
| Nassau-Dorchester & Co. Limited | Administrative & support | 2004 |
| Nava (UK) Limited | | 1982 |
| Naviq Technology UK Limited | Information & communication | 2025 |
| Nether Green Ltd. | Real estate | 1999 |
| Netsecure UK Ltd | Information & communication | 2014 |
| NEU Architects Limited | Professional & scientific | 1997 |
| New Generation Company Limited | Wholesale & retail | 2022 |
| New Harbour Investments Limited | Administrative & support | 2003 |
| New Prospect Business Solutions Limited | Information & communication | 2003 |
| New World Trust | Information & communication | 2006 |
| Newbury Buses Limited | Transport & logistics | 1985 |
| Newbury Carpentry Limited | Construction | 2002 |
| Newbury Electronics Limited | Manufacturing | 1960 |
| Newbury Racecourse Enterprises Limited | Real estate | 2001 |
| Newtown Estates Limited | Construction | 1998 |
| Next Level Exhibition Services Ltd | Construction | 2020 |
| NFM Cleaning Solutions Ltd | Professional & scientific | 2002 |
| Nightingale Recruitment (UK) Ltd | Administrative & support | 2004 |
| Niverwood Limited | Real estate | 1974 |
| NMV Property Co. Ltd | Professional & scientific | 2005 |
| Northanger Limited | Information & communication | 2024 |
| Northchapel Transport Limited | Transport & logistics | 2004 |
| Note Windsor Limited | Manufacturing | 2003 |
| Numina Consulting Ltd | Information & communication | 2003 |
| Nurofen Limited | Extraterritorial | 1967 |
| O'Neill Holdings Limited | Construction | 1993 |
| Oakcot Limited | Construction | 1999 |
| Oakview (Wokingham) Management Limited | Households | 1989 |
| Objectpro Ltd | Information & communication | 1996 |
| Occupational Therapy and Care Services Limited | Public administration | 2021 |
| Ocean to Earth Limited | Extraterritorial | 1973 |
| OCK Street Development Company (Abingdon) Limited | Real estate | 2004 |
| Offshoots Limited | Professional & scientific | 2005 |
| OK Cleaning Service Ltd | Administrative & support | 2002 |
| Old Brewhouse Residents Limited | Households | 2002 |
| Oldplan Limited | Real estate | 1998 |
| Onespace Property Solutions Limited | Real estate | 2006 |
| Onstal Ltd | Information & communication | 2006 |
| Openbook Limited | Information & communication | 1995 |
| Oppenheims Accountancy Limited | Professional & scientific | 2003 |
| Optrex Limited | Professional & scientific | 1935 |
| Oran Transport Limited | Transport & logistics | 2002 |
| Organon Systems Limited | Information & communication | 1996 |
| Orison Ltd | Real estate | 2011 |
| Osnet Limited | Information & communication | 1999 |
| OTA Solutions Limited | Wholesale & retail | 2001 |
| Otherpenny Ltd | Professional & scientific | 2006 |
| Otona Properties (Ascot) Limited | Professional & scientific | 2004 |
| Oxford Network Consultants Ltd | Information & communication | 1998 |
| Oyster Research Solutions Limited | Professional & scientific | 2007 |
| P.A. Kent Limited | Households | 1961 |
| P.C. Data & Security Ltd | Construction | 1997 |
| P.J. Decor Limited | Administrative & support | 2002 |
| Paisafare UK Ltd | Wholesale & retail | 2019 |
| PAM Fruit & VEG Limited | Wholesale & retail | 1999 |
| Pangaea Properties Limited | Real estate | 2005 |
| Paragon AV Limited | Wholesale & retail | 2017 |
| Paragon Estates (UK) Limited | Real estate | 2006 |
| Parkview Management (Slough) Limited | Households | 1997 |
| Pass IT on Limited | Information & communication | 2001 |
| Patrick HOY Associates Limited | Information & communication | 2002 |
| PAU Brasil Limited | Wholesale & retail | 2004 |
| Paul Harrap Decorators Limited | Construction | 2005 |
| Pavane Consultants Limited | Professional & scientific | 1995 |
| Paycoll Payroll Ltd | Financial services | 2008 |
| Payconnect Global Ltd | Construction | 2024 |
| PDQ Developments Limited | Wholesale & retail | 1998 |
| Peachyclean Limited | Administrative & support | 2007 |
| Pearl Dining Ltd | Hospitality | 2026 |
| Penstone Veterinary Clinic Limited | Professional & scientific | 2001 |
| Penwyvern Construction Limited | | 1984 |
| Perceptions Associates Limited | Information & communication | 2005 |
| Perfect Accountancy Services Limited | Professional & scientific | 2004 |
| Perfect Fried Chicken Limited | Hospitality | 1999 |
| Performance Events Ltd | Administrative & support | 2005 |
| Perris@Hollington Limited | Agriculture & fishing | 2002 |
| Perryton Engineering Ltd | Wholesale & retail | 2018 |
| Peter Meade Scientific Writing Ltd | Professional & scientific | 2005 |
| Peter's Roofing Contractors Limited | Construction | 2007 |
| PFC Associates Limited | Professional & scientific | 1999 |
| Pharmplex Limited | Wholesale & retail | 1997 |
| Philip Bryett Limited | Manufacturing | 1995 |
| Phitech Maintenance Services Limited | Professional & scientific | 1989 |
| PI Creative Limited | Professional & scientific | 2007 |
| Pielicious Limited | Manufacturing | 2017 |
| Pier Developments Limited | Real estate | 2000 |
| Pilgrim Media Limited | Information & communication | 2007 |
| Pillon Limited | Extraterritorial | 2007 |
| Pincott Limited | Extraterritorial | 1971 |
| Pinehill Management Company Limited | Households | 1997 |
| Pineridge Gardens Limited | Households | 1996 |
| Pippa O'Brien Development Associates Limited | Professional & scientific | 2000 |
| Planet Saturn Limited | Professional & scientific | 2001 |
| Plemaray Limited | Households | 1973 |
| Ployupper Limited | Hospitality | 1993 |
| PMD Tea Ltd | Wholesale & retail | 2018 |
| Podium Tours Limited | Professional & scientific | 2022 |
| Poly (UK) Limited | Wholesale & retail | 1992 |
| Portfolio Consulting Ltd | Professional & scientific | 2006 |