| Northerwood Systems Ltd | Information & communication | 2005 |
| Northland International Limited | Professional & scientific | 2001 |
| Northwood Properties (Fareham) Limited | Financial services | 1963 |
| Notapon Limited | Health & social care | 2012 |
| NOW Digital (East Midlands) Limited | Information & communication | 2000 |
| NOW Digital (Oxford) Limited | Information & communication | 2007 |
| NOW Digital (Southern) Limited | Information & communication | 1998 |
| NOW Digital Limited | Information & communication | 1998 |
| NOW Mortgages LLP | | 2002 |
| NPI Group Limited | Financial services | 2026 |
| NRG Digital Ltd | Information & communication | 2002 |
| Nulite Trading Limited | Administrative & support | 1999 |
| Nursted Builders Limited | Construction | 1971 |
| Nuteq Limited | Extraterritorial | 2003 |
| Nuthatch Close Residents Limited | Households | 1995 |
| Nutraq UK Ltd | Wholesale & retail | 2023 |
| NVD Convertor Ltd | Wholesale & retail | 2024 |
| O2 Skincare Limited | Other services | 2003 |
| Oak Investments Limited | Financial services | 1998 |
| Oakland Consultancy Services Limited | Professional & scientific | 1998 |
| Oakland Cottages Management Company Limited | Households | 2006 |
| Oakley GAS and Heating Limited | Manufacturing | 2004 |
| Oakley Limos Ltd | Transport & logistics | 2006 |
| Oblique Strategies Ltd | Professional & scientific | 1996 |
| OCC Investments Ltd | Construction | 2006 |
| Ocean Passages (Charter) Limited | Transport & logistics | 1999 |
| Ocean Passages Limited | Transport & logistics | 1998 |
| Oceanside Taping & Jointing Limited | Construction | 2006 |
| Ochtar Ltd | Information & communication | 2007 |
| OG Properties Limited | Real estate | 2004 |
| Ojal Corporations Ltd | Wholesale & retail | 2023 |
| OKW Enclosures Limited | Manufacturing | 1987 |
| OKW Limited | Extraterritorial | 1989 |
| Old Thorns Golf & Country Club Limited | | 1979 |
| Oliben Associates | | 2002 |
| Oliver's Battery Chiropractic Limited | Health & social care | 2021 |
| Omega Point Limited | Information & communication | 1989 |
| ON TAP (Southern) Ltd | Construction | 2003 |
| Oncall 24 Healthcare Solutions Ltd | Health & social care | 2023 |
| One Star Consulting Ltd. | Professional & scientific | 2017 |
| One Trybal (UK) Limited | Information & communication | 2000 |
| Onkey Business Ltd | Information & communication | 2005 |
| Options Autism (5) Limited | Real estate | 2006 |
| Options Day Service Limited | Health & social care | 2002 |
| Options Wellbeing Trust | Information & communication | 2003 |
| Opulent Services Limited | Construction | 2016 |
| Oram Furniture Limited | Manufacturing | 2003 |
| Orams Ltd | Professional & scientific | 2003 |
| Orchid Spa Ltd | Health & social care | 2012 |
| Orhetor Limited | Extraterritorial | 2005 |
| Origin Live Limited | Manufacturing | 2006 |
| Origo Limited | Professional & scientific | 1990 |
| Orlandi Cameron Limited | Construction | 2004 |
| Ormsby Solutions Ltd | Professional & scientific | 2021 |
| Orta Projects Limited | Information & communication | 2006 |
| OTN Computing Limited | Information & communication | 1998 |
| Otro Ltd | Professional & scientific | 2007 |
| Owlsmoor Business Services Limited | Real estate | 1982 |
| Owton Freight Limited | Real estate | 2006 |
| P & G Electrical and Building Services Limited | Construction | 2004 |
| P a E Limited | Wholesale & retail | 2005 |
| P a Keep Limited | Hospitality | 2003 |
| P a White Limited | Administrative & support | 2006 |
| P D Tools (UK) Limited | Manufacturing | 2007 |
| P J Collingwood Limited | Construction | 2007 |
| P J Hayman & Company Limited | Financial services | 1990 |
| P J Hayman Insurance Services Limited | Financial services | 1999 |
| P. & G. Wells Limited | Wholesale & retail | 1983 |
| P. Neville & SON Ltd. | Administrative & support | 2003 |
| P.A. Blake Limited | Construction | 2005 |
| P.A.W. Limited | Construction | 2003 |
| P.B. Edwards Plastering and Drylining Limited | Construction | 1995 |
| P.B.R. Services (Printers) Limited | | 1975 |
| P.J.Publishing Limited | Information & communication | 1989 |
| P.M. Brett Limited | Construction | 2000 |
| P.R. Designs Limited | Professional & scientific | 1997 |
| PA (1996) Limited | Real estate | 1996 |
| Padworth Trout Farm Limited | Agriculture & fishing | 1995 |
| Palfinger Marine UK Limited | Manufacturing | 1988 |
| Palmer Homes (Southern) Limited | Construction | 2006 |
| PAO13 Limited | Transport & logistics | 2021 |
| Paradox Quality Entertainments Limited | Information & communication | 1998 |
| Pardy & SON (Printers) Limited | Manufacturing | 2001 |
| Pardy & SON Ringwood Limited | Manufacturing | 1937 |
| Paris 003 Limited | Extraterritorial | 2006 |
| Paris Smith LLP | | 2004 |
| Parity for Disability | Health & social care | 1998 |
| Park Close (Aldershot) Management Company Limited | Real estate | 1992 |
| Park Lane (UK) Limited | Wholesale & retail | 1987 |
| Parkers Meadow Management Company Limited | Households | 2000 |
| Parkfield Retail Limited | Wholesale & retail | 2000 |
| Parkhall Private Office Ltd | Real estate | 2020 |
| Paul Hurst Thatching Limited | Construction | 2001 |
| Paul Jeffreys Limited | Real estate | 2006 |
| Paul Jobst Limited | Manufacturing | 2002 |
| Paul Quarrington Limited | Information & communication | 1997 |
| Paula Express Ltd | Transport & logistics | 2024 |
| Paultons Park Limited | Arts & recreation | 1986 |
| Payload Consultants Ltd | Professional & scientific | 2006 |
| Payroll Assured Limited | Professional & scientific | 2003 |