| MBH Southern Ltd | Construction | 2017 |
| MBM Parties Limited | Administrative & support | 2022 |
| MBM Systems Limited | Professional & scientific | 2023 |
| MBU Motors Limited | Transport & logistics | 2026 |
| MC Audit Limited | Professional & scientific | 2024 |
| MC Carraige Masters Ltd | Other services | 2024 |
| MC Consultants Limited | Professional & scientific | 2025 |
| MC Hair Design Ltd | Other services | 2020 |
| MC Pre-School Limited | Health & social care | 2025 |
| MC Secretaries Limited | Professional & scientific | 2002 |
| MC Technical Recruitment Ltd | Administrative & support | 2019 |
| MC101 Indian Cottage Ltd | Professional & scientific | 2019 |
| MCA Build Ltd | Construction | 2022 |
| Mcain Limited | Construction | 2000 |
| Mcbeth Structural Surveys Ltd | Professional & scientific | 2020 |
| Mccarthy Refrigeration Limited | Manufacturing | 2011 |
| MCD (Southern) Limited | Construction | 2018 |
| Mcdade Construction Ltd | Construction | 2024 |
| Mcfarlane Medical Limited | Health & social care | 2019 |
| Mcgee Brothers Property Design & Build Ltd | Construction | 2024 |
| Mcgee Brothers Property Development Limited | Real estate | 2018 |
| Mcgen UK Ltd | Health & social care | 2026 |
| Mcgowan's Carpentry Limited | Construction | 2017 |
| MCIC1 Ltd | Professional & scientific | 2021 |
| MCK Spray Render Ltd | Construction | 2016 |
| Mckenzie Property Solutions Ltd | Real estate | 2025 |
| Mclean Property Investment Ltd | Real estate | 2024 |
| MCM Facilities Management Limited | Administrative & support | 1962 |
| MCM Mannings Limited | Hospitality | 2014 |
| MCR Contracting Ltd | Administrative & support | 2021 |
| MD Home Improvements Ltd | Construction | 2024 |
| MD08 Ltd | Professional & scientific | 2019 |
| MDA Contractors Ltd | Construction | 2013 |
| MDI Global Solutions Limited | Financial services | 2002 |
| MDI Networks Limited | Information & communication | 2002 |
| Mdla Ltd | Transport & logistics | 2026 |
| MDM Trading Limited | Construction | 2018 |
| MDN Local Ltd | Wholesale & retail | 2019 |
| MDN Super Store Ltd | Wholesale & retail | 2023 |
| Me-Vu Ltd | Information & communication | 2025 |
| ME4 Ltd | Other services | 2019 |
| Meadair Ltd | Professional & scientific | 2019 |
| Meadens of Hythe Limited | Wholesale & retail | 2004 |
| Meadow Farm Garden Centre Limited | Wholesale & retail | 2014 |
| Meadow Farm Nursery Limited | Wholesale & retail | 2011 |
| Meadowdale Ecological Holdings Limited | Financial services | 2017 |
| Meadowdale Limited | Professional & scientific | 2013 |
| Meads Investments (Hampshire) Limited | Administrative & support | 2014 |
| Meat and Barrel Limited | Hospitality | 2014 |
| MEC Events Ltd | Arts & recreation | 2018 |
| Mechelec (Crash Repair) Limited | Wholesale & retail | 1985 |
| Mechelec (Fareham) Limited | Manufacturing | 1983 |
| Medhealth Cardiac Diagnostics Ltd | Health & social care | 2023 |
| Medhealth Ultrasound Ltd | Health & social care | 2025 |
| Media Matters Technology Limited | Manufacturing | 2004 |
| Media Services Southern Limited | Manufacturing | 2026 |
| Medica Universal Ltd | Health & social care | 2020 |
| Medication Every Day Services Limited | Wholesale & retail | 2008 |
| Medique Limited | Health & social care | 2010 |
| Meecarigno Limited | Administrative & support | 2015 |
| Meer Barber Ltd | Other services | 2023 |
| Meesak Limited | Wholesale & retail | 2021 |
| Meet Transports Ltd | Transport & logistics | 2019 |
| Mektrip Ltd | Administrative & support | 2023 |
| Melidite Limited | Financial services | 1990 |
| Meller & Petersen Limited | Construction | 2025 |
| Mengham Secretarial Agencies Limited | Professional & scientific | 1984 |
| Meon (Property) Limited | Real estate | 2024 |
| Meon Group Limited | Financial services | 2024 |
| Meon Holdings Limited | Financial services | 2020 |
| Meon Limited | Construction | 2010 |
| Meon Scientific Services Ltd | Professional & scientific | 2026 |
| Meon Services Limited | Construction | 2022 |
| Meon Technology Limited | Administrative & support | 2012 |
| MER Maid Cleans Limited | Administrative & support | 2020 |
| Mercator Cargo Holdings Limited | Financial services | 2023 |
| Mercator Cargo Systems Limited | Transport & logistics | 1991 |
| Merchants Place (Reading) Limited | Real estate | 2025 |
| Mercury House RTM Company Ltd | Households | 2017 |
| Mercury HR Ltd | Administrative & support | 2006 |
| Meritz Limited | Wholesale & retail | 2002 |
| Merlin Mortgage Management Limited | Financial services | 2004 |
| Merritt Decorators Limited | Construction | 2003 |
| Merunas Retails Ltd | Wholesale & retail | 2024 |
| MES Management Limited | Professional & scientific | 2026 |
| Metal Treatments (Portsmouth) Limited | Manufacturing | 2010 |
| Metalikart Limited | Arts & recreation | 2017 |
| Metanoia Ventures Ltd | Information & communication | 2026 |
| Metaverse VR Ltd | Information & communication | 2021 |
| Metric-Services Ltd | Construction | 2024 |
| Metty Property Management Ltd | Real estate | 2023 |
| Meylex Ltd | Construction | 2025 |
| Meñli Ltd | Wholesale & retail | 2023 |
| MF Electrical & Building Services Limited | Construction | 2013 |
| MFR Property Management Limited | Real estate | 2024 |
| MFT of Bognor Limited | Administrative & support | 2003 |
| MG Heating (Southern) Limited | Construction | 2013 |
| MG Properties (IW) Limited | Other services | 2014 |
| MG Security Services Ltd | Financial services | 2019 |
| Mg&T (Hampshire) Limited | Wholesale & retail | 2014 |