| Medical Sickness Limited | Professional & scientific | 2006 |
| Medicals First Ltd | Administrative & support | 2006 |
| Medina Bakery Limited | Manufacturing | 2006 |
| Medistop Limited | Wholesale & retail | 2000 |
| Medisure Limited | Health & social care | 2005 |
| Medscience Asia-Europe Trade Limited | Professional & scientific | 2013 |
| Medtech Telonexus Limited | Information & communication | 2023 |
| Megakey Enterprises Limited | Information & communication | 1994 |
| Mehta Holdings Limited | Administrative & support | 2005 |
| Meliora Care Group Limited | Health & social care | 2025 |
| Meltor Limited | Professional & scientific | 1980 |
| Mente Caro Ltd | Wholesale & retail | 2023 |
| Mercia Electrical Solutions Limited | Construction | 2021 |
| Mercia Manufacturing Group Limited | Financial services | 2024 |
| Mercia Roadstone Limited | Wholesale & retail | 1979 |
| Mercian Weldcraft Limited | Manufacturing | 1971 |
| Mercury Tool & Gauge Limited | Professional & scientific | 1995 |
| Mere Green Service Station Limited | Wholesale & retail | 1959 |
| Merion Hold Co II Ltd | Financial services | 2024 |
| Merion Holdco I Ltd | Financial services | 2023 |
| Merion Holdco III Limited | Financial services | 2025 |
| Merion Limited | Professional & scientific | 2015 |
| Meriroyles Limited | Administrative & support | 2006 |
| Merlin Business Services UK Ltd | Professional & scientific | 2006 |
| Merseyside Galvanizing Limited | Manufacturing | 1981 |
| Mesonax Limited | Professional & scientific | 2021 |
| Metal Assemblies Ltd | Manufacturing | 1955 |
| Metal Sections Limited | Professional & scientific | 1990 |
| Metalcast (Bilston) Limited | Manufacturing | 1994 |
| Metalcast (Holdings) Limited | Professional & scientific | 1989 |
| Metalcraft Pipework and Fabrications Limited | Manufacturing | 1985 |
| Metallisation Limited | Manufacturing | 2003 |
| Metaltreat Limited | Manufacturing | 1964 |
| Metaomega Food Limited | Wholesale & retail | 2023 |
| Metro Glazing Limited | Construction | 1980 |
| Metrogrand Limited | Professional & scientific | 1989 |
| Mezini Ltd | Transport & logistics | 2020 |
| Mfor.Net Limited | Information & communication | 2004 |
| MFP Limited | Professional & scientific | 2001 |
| Mgts Business and Training Services Limited | Education | 2000 |
| MI Glass Limited | Manufacturing | 1955 |
| MI Glass Midco Limited | Financial services | 2005 |
| Michael Jackson Controls Limited | Information & communication | 2000 |
| Mid-West Securities Limited | Real estate | 2000 |
| Midland Chassis Treatments Limited | | 1979 |
| Midland Chemicals Waste Management Limited | Water & waste | 1987 |
| Midland Domestic Limited | Wholesale & retail | 1995 |
| Midland Entertainment and Management Agency Ltd | Arts & recreation | 2006 |
| Midland Fabric & Bar Building & Civil Engineers Limited | Manufacturing | 1999 |
| Midland Group Training Services Limited | Education | 1970 |
| Midland Heart Development Limited | Construction | 2006 |
| Midland Networks Ltd | Information & communication | 2005 |
| Midland OIL Refinery Limited | Manufacturing | 2003 |
| Midland Property Dealers Limited | Real estate | 2002 |
| Midland Pump Holdings Limited | Professional & scientific | 2005 |
| Midland Recruitment Limited | Other services | 2007 |
| Midland Sporting Association Limited | Other services | 2004 |
| Midland Tool and Design Limited | Manufacturing | 1969 |
| Midlands Fencing Solutions Ltd | Other services | 2007 |
| Midlands Plastic Ltd | Manufacturing | 2010 |
| Midnight Lark Productions Limited | Information & communication | 2007 |
| Midpex Limited | Wholesale & retail | 1970 |
| Midvak Limited | Administrative & support | 2002 |
| Milegrain Limited | Professional & scientific | 2005 |
| Millfields Concrete Company Limited | Professional & scientific | 1926 |
| Millfields Investments Limited | Professional & scientific | 1938 |
| Millstone Services Limited | Professional & scientific | 2007 |
| Minamini Limited | Wholesale & retail | 2024 |
| Mini Deli Limited | Hospitality | 2007 |
| Mitchells & Butlers (IP) Limited | Professional & scientific | 2003 |
| Mitchells & Butlers (Property) Limited | Real estate | 1977 |
| Mitchells & Butlers Finance PLC | Financial services | 2003 |
| Mitchells & Butlers Holdings Limited | Financial services | 1997 |
| Mitchells & Butlers Leisure Holdings Limited | Financial services | 1991 |
| Mitchells & Butlers Leisure Retail Limited | Administrative & support | 1971 |
| Mitchells & Butlers Retail (NO 2) Limited | Hospitality | 2000 |
| Mitchells & Butlers Retail Holdings Limited | Financial services | 2003 |
| Mitchells & Butlers Retail Limited | Hospitality | 1887 |
| Mitchells and Butlers Healthcare Trustee Limited | Administrative & support | 2003 |
| Mituson Ltd. | Manufacturing | 2001 |
| MJ Mutani Mechanics Ltd | Wholesale & retail | 2022 |
| MJG Telecommunications Limited | Information & communication | 2007 |
| MJM Commercials Limited | Wholesale & retail | 2001 |
| MJM Solutions (UK) Limited | Administrative & support | 2006 |
| MJS Mobile Caravan Servicing Limited | Wholesale & retail | 2018 |
| MK Brickwork Contractors Limited | Construction | 2007 |
| MK Workwear Ltd | Wholesale & retail | 2026 |
| MKC Garage Limited | Wholesale & retail | 2005 |
| MKY Limited | Professional & scientific | 1997 |
| MLS Lighting Limited | Construction | 2006 |
| MNM Design Limited | Professional & scientific | 2007 |
| Mobile Extra Ltd | Wholesale & retail | 2011 |
| Mobile Marketing System Limited | Administrative & support | 2004 |
| Modern Furniture Direct Limited | Extraterritorial | 2009 |
| Modern Ventilation Ltd | Wholesale & retail | 2010 |
| Module 5 Design Limited | Information & communication | 2001 |
| Mojo Capital Limited | Financial services | 2024 |
| Molloy Enterprises Limited | Hospitality | 2006 |
| Money & Mortgage House Ltd | Real estate | 2002 |
| Money Adviser LLP | | 2006 |