| Loungersclothing Limited | Wholesale & retail | 2020 |
| LTL Process Controls Limited | Manufacturing | 2004 |
| M S King Limited | Construction | 2016 |
| Macleod Capital Ltd | Financial services | 2022 |
| Maida Vale Consultancy Limited | Professional & scientific | 1997 |
| Major Perks Trading Limited | Professional & scientific | 2017 |
| MAP Capital Partners Limited | Extraterritorial | 2016 |
| MAP Ventures Ltd | Professional & scientific | 2015 |
| Mapsnag Ltd | Professional & scientific | 2026 |
| Mark Kemp Farms Ltd | Agriculture & fishing | 2011 |
| Marquee Elegance Limited | Other services | 2009 |
| Marquee Hire Group Limited | Other services | 2011 |
| MAS Consulting Limited | Information & communication | 2023 |
| Masaki Properties Limited | Real estate | 2026 |
| Matthew Younger C&M Ltd | Construction | 2025 |
| Mawdesley O'Rorke & Co. Limited | Professional & scientific | 2018 |
| Maxipart | Extraterritorial | 2003 |
| MAY Premium Travel Limited | Transport & logistics | 2024 |
| Mayberry Electrical Limited | Construction | 2022 |
| Mcphersons Solicitors LLP | | 2021 |
| MDM Electrical Services Ltd | Construction | 2018 |
| Meadow Stockbridge Ltd | Hospitality | 2023 |
| MEF Construction Services Ltd | Construction | 2010 |
| Mick Caulfield Roofing Limited | Construction | 2002 |
| Millrise Limited | Information & communication | 2024 |
| Millway Projects Limited | Construction | 2015 |
| Mitre Peak Lofts Ltd | Construction | 2020 |
| Mlama Ltd | Public administration | 2019 |
| MLC Homes Ltd | Real estate | 2022 |
| Moyles Place Management Company Limited | Households | 2019 |
| MUD on the Road Ltd | Information & communication | 2024 |
| My Bridal ERA Boutique Ltd | Wholesale & retail | 2026 |
| Natural Carbon Capital Limited | Financial services | 2022 |
| Nelson Close Management Company Ltd | Real estate | 2009 |
| Newlands Racing Limited | Arts & recreation | 2023 |
| Newman's Decorative Living Limited | Wholesale & retail | 2019 |
| Norfolk House Limited | Professional & scientific | 1981 |
| Nova AI Ltd | Professional & scientific | 2025 |
| Novus 24 Ltd | Administrative & support | 2024 |
| Novus IOW LLP | | 2024 |
| NTP Consulting Ltd | Information & communication | 2010 |
| Nuffield and Leyland Tractor Club Ltd | Arts & recreation | 2023 |
| Nutravite Limited | Professional & scientific | 1993 |
| Nutrivit Limited | Manufacturing | 1993 |
| O'Pork Property Enterprises Limited | Financial services | 2023 |
| Oceanedia Sailing Holidays Limited | Administrative & support | 2022 |
| Odaiba Limited | Professional & scientific | 2013 |
| Old Forge Hursley Ltd | Real estate | 2024 |
| Old Fromans Farm Limited | Real estate | 2000 |
| One-Two Check Ltd | Information & communication | 2025 |
| Options Flooring Limited | Wholesale & retail | 2004 |
| Orchard Mews (Southbourne) Management Company Limited | Households | 2025 |
| Orchid Direct Ltd | Wholesale & retail | 2020 |
| OSL Benefits Limited | Financial services | 2024 |
| Ottoman Developments Ltd | Real estate | 2011 |
| Ottoman Manor Limited | Real estate | 2024 |
| OUR App Limited | Information & communication | 2023 |
| Over the Hill Ltd | Real estate | 2019 |
| P E P Assets Limited | Real estate | 2022 |
| P.A.Reed Carpentry & Building Limited | Construction | 2011 |
| P.B.C. Builders (Southampton) Limited | | 1964 |
| Park Farm Somborne Management Company Limited | Administrative & support | 2011 |
| Paul Jones & Co Building Contractors Limited | Construction | 2019 |
| Pearse Products Group Limited | Wholesale & retail | 1996 |
| Pelican Worldwide Trading (UK) Ltd | Wholesale & retail | 2023 |
| Peregrine Livestock Ltd | Agriculture & fishing | 2022 |
| Pierdor Limited | Hospitality | 1995 |
| Pinxton Securities Limited | Administrative & support | 2016 |
| PIP GP 1 Limited | Financial services | 2015 |
| PIP GP 2 Limited | Financial services | 2015 |
| PJJ Consulting Limited | Professional & scientific | 2024 |
| Plain Sailing Driving School Ltd | Administrative & support | 2015 |
| Plumbtek Southern Ltd | Construction | 2020 |
| PMP Financial Solutions Ltd | Professional & scientific | 2025 |
| Pocket Applications Limited | Professional & scientific | 2013 |
| Pope Lettings Ltd | Real estate | 2019 |
| Pope Plan and Build Limited | Construction | 2013 |
| Portcullis Joinery Ltd | Manufacturing | 2013 |
| Portshores Limited | | 1983 |
| Positive Integers Ltd | Professional & scientific | 2024 |
| Power Grid Consultancy Ltd | Extraterritorial | 2025 |
| Power Management Engineering Limited | Construction | 2000 |
| Powerhouse Productions Limited | Information & communication | 1985 |
| PRB Property Group Limited | Financial services | 2022 |
| Precious & Partners Ltd | Professional & scientific | 2025 |
| Prego Deli Ltd | Hospitality | 2017 |
| Premier Wildlife Services Limited | Agriculture & fishing | 2017 |
| Present Diary Companies Ltd | Extraterritorial | 2007 |
| Pretty Perfect Gifts Limited | Wholesale & retail | 2021 |
| Professional Brickwork Limited | Construction | 2017 |
| Profiler Music Limited | Information & communication | 2020 |
| Projects in Timber Limited | Manufacturing | 2023 |
| Propernomics Ltd | Professional & scientific | 2010 |
| Provenance Investment Partners I (GP) LLP | | 2015 |
| Provenance Investment Partners Management LLP | | 2015 |
| Puffin Consulting Limited | Professional & scientific | 2013 |
| Punch of London Limited | Wholesale & retail | 2023 |
| Purenumbers Accounting Limited | Professional & scientific | 2005 |
| Quantumfutureai Ltd | Information & communication | 2025 |
| Quayvalley Limited | Information & communication | 2003 |