| Nkhairlounge Ltd | Other services | 2025 |
| NL Consulting and Solutions Ltd | Information & communication | 2021 |
| NNN Services Ltd | Transport & logistics | 2025 |
| NO1SON Limited | Information & communication | 2010 |
| Noahs Plumbing & Heating Ltd | Construction | 2025 |
| Nobes Surfacing Ltd | Construction | 2018 |
| Noden Health Limited | Health & social care | 2025 |
| Nolan Management Group Ltd | Construction | 2026 |
| Noon Spoons Limited | Administrative & support | 2003 |
| North Groundworks & Building Ltd | Construction | 2025 |
| Northfield Renovations Limited | Real estate | 2021 |
| Northworx Limited | Construction | 2017 |
| NPD Global Limited | Administrative & support | 2013 |
| NU Kitchen Limited | Construction | 2019 |
| NY Regulatory Services Ltd | Professional & scientific | 2021 |
| Oak and Pine Gardening Ltd | Administrative & support | 2022 |
| Oak and Pine Landscaping Ltd | Administrative & support | 2022 |
| Oakland Park Limited | Agriculture & fishing | 2023 |
| Oakley Green Conservatories Thatcham Ltd | Construction | 2022 |
| Oakmount Financial Services Ltd | Financial services | 2017 |
| Oasis EA Holdings Limited | Professional & scientific | 2004 |
| Oasis Land and New Homes Limited | Real estate | 2020 |
| Oasis Lettings & Management Ltd | Real estate | 2019 |
| Oasis Private Clients Limited | Real estate | 2024 |
| Oasis Sales Ltd | Real estate | 2004 |
| Oasis Short Term Lettings Limited | Real estate | 2023 |
| ODP Protective Consultancy Ltd | Administrative & support | 2025 |
| OJ White Ltd | Construction | 2025 |
| OJE Autoservices Ltd | Wholesale & retail | 2022 |
| OJM Farm and Equine Limited | Wholesale & retail | 2013 |
| Old Briar Property Services Limited | Construction | 2012 |
| Oldbury IT Solutions Limited | Information & communication | 2007 |
| OLI Transport Ltd | Transport & logistics | 2025 |
| Oliver Patrick Ltd | Health & social care | 2020 |
| One Truck Solution Ltd | Wholesale & retail | 2016 |
| Onpoint Electrical UK Limited | Construction | 2018 |
| Orbi-Tel Limited | Administrative & support | 1984 |
| Ostrich Media Management Limited | Administrative & support | 2014 |
| OUR Fit Hub Thatcham Ltd | Arts & recreation | 2025 |
| Outdoorartsuk Ltd | Arts & recreation | 2001 |
| Oven Clean Done Ltd | Administrative & support | 2018 |
| Owlport Limited | Professional & scientific | 2001 |
| Oxbow Holdings Ltd | Real estate | 2020 |
| Oxfordshire Tennis Ltd | Arts & recreation | 2014 |
| Oxsydi Holdings Limited | Real estate | 2025 |
| P.M.P. Management Services Ltd | Professional & scientific | 1999 |
| PAB Financial Services Limited | Financial services | 2015 |
| Packme Limited | Wholesale & retail | 2000 |
| Packpress Limited | Information & communication | 1996 |
| PAD Electrics Limited | Construction | 2013 |
| Paisley Brown Ltd | Professional & scientific | 2015 |
| Panabery Ltd | Information & communication | 2015 |
| Pangbourne Keys Ltd | Hospitality | 2014 |
| Papadam Spice Limited | Hospitality | 2014 |
| Parachute Studios Ltd | Information & communication | 2009 |
| Parr Physiques Ltd | Arts & recreation | 2024 |
| Patel Property Lettings Limited | Real estate | 2024 |
| Pathfinder Child Care Limited | Education | 2006 |
| Patlec Services Ltd | Construction | 2012 |
| PAW Payments Ltd | Information & communication | 2026 |
| Pawtrition Ltd | Wholesale & retail | 2025 |
| PBW Motor Sports Ltd | Administrative & support | 2014 |
| Pearce Plumbing & Heating Limited | Construction | 2000 |
| Peledom Ltd | Real estate | 2022 |
| Pelican House Management Company (Newbury) Limited | Households | 2005 |
| Penney Advisory Ltd | Professional & scientific | 2026 |
| Perception Labs Ltd | Extraterritorial | 2017 |
| Permanent Solutions Ltd | Wholesale & retail | 2016 |
| PES Design and Developments Ltd | Professional & scientific | 2018 |
| Peter Rosinski Limited | Administrative & support | 2007 |
| Pharmasas Consulting Limited | Administrative & support | 2010 |
| Phila Consulting Limited | Information & communication | 2024 |
| Philip Castang Properties Limited | Real estate | 1962 |
| Phireon Innovo Joint Venture Limited | Professional & scientific | 2022 |
| Phone Repair Prime Ltd | Wholesale & retail | 2026 |
| PIG Inns Limited | Professional & scientific | 2011 |
| Pijs Ltd | Hospitality | 2025 |
| Pinewood Garage Limited | Wholesale & retail | 2016 |
| Pink City Properties Ltd | Real estate | 2023 |
| Piper Autos Limited | Wholesale & retail | 2018 |
| Pipoca Limited | Hospitality | 2018 |
| PL Industries Ltd | Information & communication | 2015 |
| Planfit Limited | Information & communication | 2018 |
| PM Resources Ltd | Information & communication | 2025 |
| PM Watson Consulting Ltd | Professional & scientific | 2014 |
| Pondside Management Company Limited | Households | 1995 |
| POP Inn Cafe (Thatcham) Limited | Other services | 2019 |
| Power Gardening (Slough) Limited | Financial services | 1956 |
| PR Controls Ltd | Construction | 2012 |
| Pragnahay Limited | Administrative & support | 2014 |
| Pratleys Carpenters Ltd | Construction | 2014 |
| PRC Carpets and Blinds Ltd | Other services | 2023 |
| Precision Car Care Ltd | Wholesale & retail | 2026 |
| Precision Gardens & Driveways Ltd | Administrative & support | 2025 |
| Precisionlean Consulting Ltd | Professional & scientific | 2025 |
| Prestigous Ltd | Administrative & support | 2024 |
| Prestons Installations Ltd | Construction | 2024 |
| Primary Health IT Limited | Information & communication | 2011 |
| Prime Water Solutions Ltd | Water & waste | 2024 |
| Primeride Motors Limited | Wholesale & retail | 2025 |