| Lexington Court RTM Company Limited | Households | 2012 |
| Lg&P Holdings Ltd | Financial services | 2023 |
| Lg&P Limited | Water & waste | 2008 |
| Licensed Hairdresser Limited | Other services | 2009 |
| Licensed Support Services Ltd | Professional & scientific | 2011 |
| Liddell Estates Limited | Real estate | 2001 |
| Liddell Farms Limited | Agriculture & fishing | 2016 |
| Liddell Holdings (Wessex) Limited | Financial services | 2011 |
| Life Expectations Limited | Administrative & support | 2023 |
| Life Stream Healthcare Limited | Information & communication | 2007 |
| Lifetime Care Group Limited | Health & social care | 2017 |
| Lift & Shift Logistics Limited | Transport & logistics | 2020 |
| Lily's Food Services Ltd | Hospitality | 2025 |
| Lime Business Services Ltd | Administrative & support | 2018 |
| Line Bridge Limited | Professional & scientific | 2017 |
| Linkedin Consulting Ltd | Administrative & support | 2012 |
| Linkedin Invest Ltd | Real estate | 2021 |
| Little Lillies Designs Limited | Arts & recreation | 2018 |
| Little Meadow (Timsbury) Management Limited | Households | 2021 |
| Little Miss Pamper Ltd | Other services | 2022 |
| Littlebigbox Limited | Information & communication | 2021 |
| Littleton Shaw Limited | Information & communication | 1996 |
| Live Odyssey Global Limited | Arts & recreation | 2025 |
| Live Odyssey Promotions Ltd | Arts & recreation | 2024 |
| LJE Planning Limited | Professional & scientific | 2011 |
| LJW Anaesthetics Ltd | Health & social care | 2022 |
| LMO Futures Limited | Financial services | 2026 |
| LMP Gynaecology Limited | Health & social care | 2024 |
| LNC Medical Ltd | Health & social care | 2023 |
| Lobo & Moras Limited | Health & social care | 2015 |
| Lockdon Ltd | Professional & scientific | 2017 |
| Lofi Industries Limited | Professional & scientific | 2013 |
| Lombardy Group Limited | Real estate | 2020 |
| London Investopedia Limited | Other services | 2015 |
| Longcroft Luxury Cat Hotel Romsey Ltd | Other services | 2019 |
| Lorenzo & Andy Ltd | Education | 2022 |
| Louis Powell Property Services Ltd | Professional & scientific | 2024 |
| Louisa DE Lange Limited | Information & communication | 2016 |
| Lound Hive Limited | Manufacturing | 2020 |
| Love's Labours Limited | Administrative & support | 2019 |
| Lovell Creative Consulting Ltd | Professional & scientific | 2024 |
| Lovetoswim Hampshire Limited | Wholesale & retail | 2011 |
| Lovin Life Media Ltd | Information & communication | 2025 |
| Lower Common Road Stores Limited | Wholesale & retail | 2003 |
| LSS Group Ltd | Professional & scientific | 2020 |
| LSS Licence Holding Limited | Financial services | 2022 |
| LUC Purveyor of Fine Foods Limited | Wholesale & retail | 2016 |
| Lugh Ltd | Information & communication | 2018 |
| Luminique Events Limited | Administrative & support | 2019 |
| Lupinporch Property Limited | Real estate | 2006 |
| LUX & Co Services Ltd | Financial services | 2023 |
| Luxury Short Stays Ltd | Real estate | 2016 |
| Lyness O'Connor Limited | Professional & scientific | 2022 |
| Lyon Heart Limited | Health & social care | 2015 |
| M & C King Limited | Construction | 2008 |
| M & J Transport (Southampton) Ltd. | Extraterritorial | 2014 |
| M & M Smith Limited | Professional & scientific | 2010 |
| M & S Travel (South East) Limited | Transport & logistics | 2022 |
| M Black Training Ltd | Financial services | 2011 |
| M C Rudd Holdings Limited | Administrative & support | 2017 |
| M Stubbs Interiors Ltd | Construction | 2011 |
| M Venn Construction Ltd | Construction | 2021 |
| M W Video Systems Limited | Manufacturing | 1979 |
| M&W Lettings Ltd | Real estate | 2024 |
| M.G.Webber Building & Construction Limited | Construction | 2024 |
| M2K Care Limited | Health & social care | 2023 |
| Macaw Medical Services Limited | Health & social care | 2019 |
| Mace Transport Ltd | Transport & logistics | 2019 |
| Mackie Medical Limited | Health & social care | 2019 |
| Macraegold Ltd | Wholesale & retail | 2026 |
| Maddison Court Management Company Limited | Households | 2021 |
| Made by MAX Ltd | Construction | 2026 |
| Magenta Swan Ltd | Administrative & support | 2023 |
| Magic Numbers (UK) Limited | Professional & scientific | 2011 |
| Magnum Events Ltd | Administrative & support | 2004 |
| MAI Nguyen Mortgage Ltd | Financial services | 2020 |
| Mainly Sparks Limited | Construction | 2020 |
| Mainsborough Developments Limited | Construction | 2024 |
| Malcolm Woodruff Limited | Professional & scientific | 2002 |
| Malcolmania Ltd | Information & communication | 2026 |
| Management and Service Solutions Ltd | Manufacturing | 2022 |
| Mandarin Chef (Romsey) Limited | Hospitality | 2018 |
| Manderley Commercial Services Limited | Real estate | 2013 |
| Manor Motorhomes Ltd | Wholesale & retail | 2015 |
| Manor Nursery Estates Ltd | Construction | 2019 |
| Manor Nursery Limited | Construction | 2014 |
| MAR Sports Ortho LLP | | 2025 |
| Marco Adamo Surgery Ltd | Health & social care | 2017 |
| Marine Electrical Design Services Ltd | Professional & scientific | 2023 |
| Maritime Zone Solutions Ltd | Professional & scientific | 2010 |
| Mark 1 Glazing Maintenance Limited | Administrative & support | 2018 |
| Mark Bridger Consulting Limited | Information & communication | 2023 |
| Mark David Seddon Ltd | Information & communication | 2024 |
| Mark Hooton Limited | Professional & scientific | 2002 |
| Marka Training and Development Limited | Education | 2024 |
| Marshall Technical Services Ltd | Professional & scientific | 2024 |
| Martin Thomas Associates Limited | Professional & scientific | 2002 |
| Martock Diesel Services Limited | Manufacturing | 2019 |
| Mase Mare Ltd | Manufacturing | 2017 |
| Masons HPS Limited | Construction | 2016 |