| North & Sons Limited | Agriculture & fishing | 2012 |
| North Light Solutions Limited | Administrative & support | 2011 |
| North Ridge Horizons Limited | Professional & scientific | 2019 |
| NOT Just SEO Limited | Information & communication | 2014 |
| NOT Your Basic Mama Limited | Professional & scientific | 2023 |
| Novare 9 Ltd | Professional & scientific | 2025 |
| Novum Medtech Limited | Manufacturing | 2021 |
| NS Food Tech Consultancy Limited | Hospitality | 2024 |
| Nspire Coaching Ltd | Professional & scientific | 2025 |
| Nubar Limited | Real estate | 2013 |
| Nucleus Media Group Limited | Financial services | 2025 |
| Nugent Consultancy Ltd | Professional & scientific | 2025 |
| Nursery in a Yurt Limited | Education | 2021 |
| NV London Calcutta Limited | Wholesale & retail | 2014 |
| Oak Tree Gardens Picket Piece Management Limited | Households | 2019 |
| Oakbank Windows & Roofline Ltd | Construction | 2019 |
| Oakes Coffee Ltd | Manufacturing | 2023 |
| Oakfield Yard Property Management Ltd | Real estate | 2025 |
| Oaktree Accountants Limited | Financial services | 2018 |
| Oasis Maintenance Group Ltd | Administrative & support | 2025 |
| Ocean Kind Property Ltd | Real estate | 2022 |
| Oceanect Ltd | Professional & scientific | 2015 |
| Octo Plumbing & Bathrooms Limited | Construction | 2023 |
| October Project Services Ltd | Professional & scientific | 2020 |
| OGB Logistics Ltd | Transport & logistics | 2019 |
| Ogorod Ltd | Wholesale & retail | 2018 |
| OH NOH Ltd | Transport & logistics | 2025 |
| Olas Divine Concepts Ltd | Information & communication | 2021 |
| Old Bones Fabrications Ltd | Wholesale & retail | 2021 |
| Old Georgians Rugby Football Club | Arts & recreation | 2019 |
| Old Georgians Rugby Trading and Supporters Group Limited | Arts & recreation | 2019 |
| Old Soul Blues Ltd | Professional & scientific | 2023 |
| Oleron Limited | Professional & scientific | 2017 |
| Olivefield Group Ltd. | Real estate | 2009 |
| Olivia Bell Design Limited | Other services | 2010 |
| Ollie’S Logistics Ltd | Other services | 2025 |
| Olthor Ltd | Construction | 2022 |
| OM Same Day Ltd | Transport & logistics | 2026 |
| Omnific Civil Engineering and Outdoor Electrical Ltd | Construction | 2017 |
| Onajite Ltd | Health & social care | 2021 |
| Onions Ltd | Administrative & support | 2008 |
| Onlinesensors Ltd | Wholesale & retail | 2022 |
| Only Van to Go Ltd | Transport & logistics | 2025 |
| Open Sense Ltd | Professional & scientific | 2017 |
| Opera Edition Ltd | Information & communication | 2024 |
| Opsure Group Ltd | Professional & scientific | 2026 |
| Optimizing Life Ltd | Wholesale & retail | 2023 |
| Oracle Broadcast Systems Limited | Information & communication | 2019 |
| Orama Luxury Home Fragrances Ltd | Wholesale & retail | 2025 |
| Orange County Fashion and Leisure Limited | Wholesale & retail | 2026 |
| ORI Healthcare Ltd | Public administration | 2024 |
| Origin Electric UK Ltd | Information & communication | 2021 |
| Origin Project Management Solutions Ltd | Professional & scientific | 2014 |
| Origin Pure UK Ltd | Wholesale & retail | 2022 |
| Origin Training Project Limited | Agriculture & fishing | 2011 |
| ORO Living Ltd | Real estate | 2025 |
| Osborn Creative Ltd | Professional & scientific | 2025 |
| Osborne Court Management (Andover) Limited | Real estate | 1995 |
| Oschen Limited | Wholesale & retail | 2023 |
| Osco Design Limited | Administrative & support | 2017 |
| Osco Europe Limited | Wholesale & retail | 1998 |
| Osco Nominees Limited | Administrative & support | 2019 |
| Osteobeth Ltd | Health & social care | 2026 |
| OT Livestock Ltd | Wholesale & retail | 2026 |
| OTM Apprenticeships Ltd | Education | 2005 |
| OTS Company NO 2 Ltd | Extraterritorial | 2026 |
| OTS Company NO 3 Ltd | Extraterritorial | 2026 |
| Otto Productions Ltd | Information & communication | 2006 |
| OUR Andover CIC | Administrative & support | 2018 |
| Outersolve Limited | Information & communication | 1988 |
| Outlook Counselling Ltd | Wholesale & retail | 2020 |
| Overton and Basingstoke Taekwondo | Arts & recreation | 2010 |
| Oxenwood Ltd | Manufacturing | 2024 |
| Oxford Radiology Courses Limited | Health & social care | 2020 |
| Oxleycare Holdings Limited | Financial services | 2022 |
| Oxleycare Property Limited | Financial services | 2022 |
| OXY Cars Ltd | Transport & logistics | 2023 |
| OXY Logistics Ltd | Transport & logistics | 2016 |
| Oyster Advisor Limited | Professional & scientific | 2024 |
| Oystergate Property Limited | Real estate | 2019 |
| Ozone Industries Limited | Manufacturing | 1994 |
| P & L Property Group Limited | Real estate | 2023 |
| P H Management Company Limited | Other services | 2006 |
| P.A.Hilton Limited | Manufacturing | 1962 |
| P.B.E.J.A Company Limited | Administrative & support | 2019 |
| P4 Projects Ltd | Construction | 2023 |
| PA Cleaning Services (Basingstoke) Ltd | Other services | 2012 |
| Package Control (U.K.) Limited | Transport & logistics | 1991 |
| Padable Ltd | Manufacturing | 2011 |
| Page and Page House Ltd | Financial services | 2024 |
| Pages Building Solutions Ltd | Construction | 2021 |
| PAK Lumia Limited | Wholesale & retail | 2026 |
| Palestine Group Ltd | Real estate | 2023 |
| Paleta Twist Ltd | Hospitality | 2024 |
| Palma Origin Co. Limited | Wholesale & retail | 2025 |
| Paneoh Limited | Financial services | 2013 |
| Panorama Business Solutions Ltd | Information & communication | 2022 |
| Pappa Limited | Administrative & support | 2023 |
| Paprizel Ltd | Transport & logistics | 2025 |
| Paradigm Horizon Investments Limited | Financial services | 2025 |