| Just Wood (Southern) Limited | Construction | 2007 |
| Justacoustic Ltd | Information & communication | 2018 |
| K Horn Professional GRP Repairs Limited | Arts & recreation | 2002 |
| KAE Creative Limited | Wholesale & retail | 2024 |
| KB 49 Limited | Professional & scientific | 2003 |
| Kingston Crescent RTM Ltd | Households | 2018 |
| Kirbuild Ltd | Construction | 2014 |
| Kirwan Property Services Ltd | Real estate | 2024 |
| Koop Prep Meals Ltd | Extraterritorial | 2019 |
| KRB Financial Ltd | Financial services | 2022 |
| KUT Carbon Ltd | Construction | 2022 |
| KW Properties (Hampshire) Limited | Construction | 2017 |
| L & W (Portsmouth) Ltd | Real estate | 2012 |
| L'Amie Consulting Ltd | Professional & scientific | 2025 |
| L.P Tree Services Ltd | Agriculture & fishing | 2023 |
| Labscience Ltd | Professional & scientific | 2008 |
| Lakesville Limited | Information & communication | 2006 |
| Lamdin Properties LLP | | 2003 |
| Landgate Consultants Limited | Administrative & support | 2023 |
| Landgate Facades Limited | Administrative & support | 2026 |
| Langstone (Havant) Properties Limited | Real estate | 1959 |
| Laoh Limited | Wholesale & retail | 2024 |
| Lewis Marquees (Westbourne) Limited | Manufacturing | 1997 |
| Lhdcarstoeurope Ltd | Other services | 2017 |
| Lighthouse Drone Company Ltd | Information & communication | 2020 |
| Lime & Marble Ltd | Construction | 2021 |
| Limitless Energy Solutions Limited | Construction | 2020 |
| Linden Point Limited | Professional & scientific | 1996 |
| Linen Guild LP | | 2015 |
| Linnies Fashions Ltd | Other services | 2011 |
| Little Learners Pre-School Limited | Education | 2013 |
| Little Peoples Nursery (Portsmouth) Limited | Education | 2010 |
| Livebetter Physiotherapy Ltd | Health & social care | 2021 |
| Lived in Interiors Ltd | Professional & scientific | 2022 |
| LJH Building Limited | Real estate | 2023 |
| LJH Electrical Southern Ltd | Construction | 2019 |
| LJH Property Services Southern Limited | Construction | 2024 |
| LK Family Law & Mediation Limited | Professional & scientific | 2014 |
| Logramo Ltd | Professional & scientific | 2020 |
| London Noore Ltd | Wholesale & retail | 2025 |
| Longie Ltd. | Real estate | 2025 |
| LSA Supplies Ltd | Wholesale & retail | 2020 |
| LTP Vehicle Repairs Limited | Wholesale & retail | 2023 |
| Lucky EMS Ltd | Hospitality | 2025 |
| Lumley Cards Limited | Wholesale & retail | 2025 |
| Lumley Marketing Ltd | Professional & scientific | 2024 |
| Lyleoak Limited | Other services | 2001 |
| M Russell Tree Specialists Ltd | Agriculture & fishing | 2015 |
| Madeera Wines Ltd | Other services | 2019 |
| Magil Ltd | Real estate | 2024 |
| MAI Virtual Assistants Ltd | Administrative & support | 2024 |
| Marine Bespoke Limited | Professional & scientific | 2024 |
| Marlow Harding Enterprises Ltd | Financial services | 2022 |
| Marqsman Bespoke Limited | Manufacturing | 2026 |
| Marqsman Ltd | Manufacturing | 2023 |
| Marshall Ergonomics Limited | Professional & scientific | 2000 |
| Marshallcuts Limited | Other services | 2025 |
| Marshglen Property Management Limited | Households | 1994 |
| Martin Paffey & Sons Limited | Construction | 2023 |
| Martindale Property Maintenance Limited | Construction | 2003 |
| Martlet International Limited | Professional & scientific | 2020 |
| Mary Puppins Pet Pantry Limited | Wholesale & retail | 2020 |
| Masterfit Contracts Ltd | Construction | 2026 |
| Masterfit EPG Ltd | Construction | 2024 |
| Masterfit Group Ltd | Construction | 2024 |
| Masterfit Ltd | Construction | 2022 |
| Matimusic Ltd | Arts & recreation | 2022 |
| Mavele Swimwear Limited | Wholesale & retail | 2015 |
| Mayfield Estates Southern Limited | Real estate | 1999 |
| MB Cleaning (South) Limited | Administrative & support | 2017 |
| Mcdill Media Limited | Arts & recreation | 2016 |
| MCJ Hill Ltd | Other services | 2022 |
| Mckellar & Nicolson Ltd | Real estate | 2020 |
| Mcwilliams Consulting Ltd | Professional & scientific | 2014 |
| MDR Estate Planning Ltd | Professional & scientific | 2020 |
| Media Market Consultants Limited | Professional & scientific | 2017 |
| Mediation NOW Limited | Professional & scientific | 2007 |
| Meon House Limited | Households | 2017 |
| Merco Place Limited | Hospitality | 2005 |
| Mercury Garage Limited | Wholesale & retail | 2002 |
| Metalwars Limited | Information & communication | 2004 |
| Metropolitan Investments Limited | Extraterritorial | 2008 |
| Metspin Limited | Manufacturing | 1979 |
| Millstream Productions (Holdings) Limited | Financial services | 2019 |
| Millstream Productions Ltd | Information & communication | 2011 |
| Mindworks Trustees Limited | Professional & scientific | 2017 |
| MKH Civil Engineering Limited | Construction | 2012 |
| Mode Electrical Solutions Ltd | Construction | 2021 |
| Mode Ltd | Construction | 2000 |
| Mode Property Group Ltd | Real estate | 2021 |
| Mokadi Media Ltd | Education | 2022 |
| Molango Ltd | Information & communication | 2025 |
| Monks Hill Books Limited | Wholesale & retail | 2011 |
| More in Time Limited | Professional & scientific | 2023 |
| Morris Customs Ltd | Manufacturing | 2023 |
| Mortgage Source (Southsea) Ltd | Financial services | 2018 |
| MPA Brickwork Limited | Construction | 2009 |
| MS Consumables Limited | Wholesale & retail | 2022 |
| Mulberry Contractors Limited | Agriculture & fishing | 2009 |
| Multihull Solutions Limited | Wholesale & retail | 2005 |