| Marie LE BON Limited | Health & social care | 2013 |
| Mark Duffy Ltd | Professional & scientific | 2021 |
| Mark Gibbs Interim Services Ltd | Professional & scientific | 2025 |
| Mark J Wood Consultants Limited | Administrative & support | 2024 |
| Mark Mcghee Limited | Professional & scientific | 2017 |
| Mark Pickford Plastic and Hand Surgery Ltd | Health & social care | 2022 |
| Mark!T Freedom Ltd | Wholesale & retail | 2023 |
| Market Recruitment Ltd | Administrative & support | 2012 |
| Marketing Masters Limited | Professional & scientific | 2003 |
| Markey & Williams-Markey Limited | Health & social care | 2025 |
| Markhor Properties Limited | Real estate | 2024 |
| Marktlink North UK M&A Ltd | Administrative & support | 2022 |
| Marler Consulting Limited | Professional & scientific | 2021 |
| Marquee Estates Limited | Real estate | 2016 |
| Mars Cheshire Holdings Limited | Financial services | 2024 |
| Marshall Artist Holdings Ltd | Wholesale & retail | 2020 |
| Marshall Grey Ltd | Professional & scientific | 2021 |
| Marshalls Land Services Ltd | Agriculture & fishing | 2017 |
| Marshmallow Pets Limited | Wholesale & retail | 2024 |
| Marshman Fitness Equipment Limited | Wholesale & retail | 2001 |
| Martell Estates Ltd | Real estate | 2025 |
| Martem Europe Limited | Administrative & support | 2009 |
| Martin Jones Plastic Surgery Ltd | Health & social care | 2021 |
| Martin Williams Casino Equipment Ltd | Administrative & support | 1995 |
| Martrad Finance Limited | Financial services | 2009 |
| Marwood Media Ltd | Professional & scientific | 2020 |
| Mason Hayes Education Services Limited | Professional & scientific | 2019 |
| Mason Hayes Estates Limited | Real estate | 2021 |
| Mason Hayes Holdings Limited | Financial services | 2021 |
| Mason Hayes Limited | Professional & scientific | 1997 |
| Masque LAB Limited | Wholesale & retail | 2025 |
| Mass Construct Limited | Construction | 2021 |
| Mass Innovations Ltd | Professional & scientific | 2023 |
| Masterclass by G Aesthetics Ltd | Other services | 2024 |
| Masterly Management Limited | Real estate | 2002 |
| Matahari Ltd | Wholesale & retail | 2024 |
| Matchday Performance Ltd | Arts & recreation | 2022 |
| Matr Personnel Ltd | Administrative & support | 2024 |
| Matrix Real Estate Investments Limited | Professional & scientific | 2016 |
| Matrix Wealth Management Limited | Professional & scientific | 2007 |
| Matt Evison Medical Ltd | Health & social care | 2018 |
| Matt Frodsham Limited | Arts & recreation | 2015 |
| Matthew Adelekan Consultancy Ltd | Health & social care | 2015 |
| Matthew Cahill Consulting Limited | Health & social care | 2014 |
| Matthew Steele Landscaping Limited | Other services | 1996 |
| Mauldeth Road Flats Maintenance Company Limited | Real estate | 1977 |
| MAX Hunt Medical Limited | Health & social care | 2025 |
| Maxem Properties Limited | Real estate | 2016 |
| MAY Nineteen Ltd | Administrative & support | 2003 |
| Mayanaya Limited | Health & social care | 2016 |
| Mayfield Road Management Company Limited | Real estate | 2004 |
| Maynard Procurement Solutions Limited | Administrative & support | 2013 |
| Mbbs Property Group Limited | Real estate | 2024 |
| MC Medical Experts Ltd | Health & social care | 2026 |
| Mc&D Limited | Health & social care | 2022 |
| Mccamley Architects Ltd | Professional & scientific | 2020 |
| Mccaslin Art Advisory Limited | Professional & scientific | 2001 |
| Mccaul Surgery Ltd | Health & social care | 2013 |
| Mccormick Asset Management Limited | Financial services | 2024 |
| Mccormick Consulting Limited | Information & communication | 1994 |
| MCD Utility Solutions Limited | Construction | 2020 |
| Mcdonald Knight Ltd | Health & social care | 2019 |
| MCK Design Limited | Professional & scientific | 2024 |
| Mclarnon Holdings Limited | Health & social care | 2024 |
| Mclaughlin Orthopaedics Ltd | Health & social care | 2019 |
| Mclennan Knight Recruitment Limited | Administrative & support | 2026 |
| Mcnulty Architects Limited | Professional & scientific | 2014 |
| Mcpix Ltd | Professional & scientific | 2005 |
| MCR Engineering Solutions Ltd | Professional & scientific | 2016 |
| MCR Gate Swanick Ltd | Hospitality | 2025 |
| MCR Hideout Ltd | Hospitality | 2025 |
| Mcstroman Limited | Health & social care | 2024 |
| MCT Property Developments Limited | Construction | 2026 |
| Mcwhirter Scott Limited | Health & social care | 2021 |
| Mcwood Holdings Ltd | Real estate | 2025 |
| MDB Clinical & Legal Consultancy Ltd | Health & social care | 2024 |
| MDB Systems Ltd | Construction | 2025 |
| MDS Compliance Consultancy Services Limited | Professional & scientific | 2025 |
| MED E Care Limited | Health & social care | 2024 |
| Medbond Limited | Health & social care | 2022 |
| Medi Laser Clinic Ltd | Health & social care | 2024 |
| Medi Luxe Ltd | Wholesale & retail | 2024 |
| Medi-Ii Ltd | Professional & scientific | 2014 |
| Media Star Maker Ltd | Professional & scientific | 2018 |
| Mediaville Research Limited | Professional & scientific | 2008 |
| Medical & Industrial GAS Services Limited | Professional & scientific | 2012 |
| Medical Accountants Limited | Professional & scientific | 2008 |
| Medical Dental Insurance Agency Limited | Professional & scientific | 2001 |
| Medical Skin Solutions Ltd | Health & social care | 2006 |
| Medicalaccountants.Com Limited | Professional & scientific | 2008 |
| Medicocg Ltd | Health & social care | 2019 |
| Medicotm Ltd | Health & social care | 2019 |
| Medics Recruitment International Limited | Real estate | 2011 |
| Mediwest Limited | Health & social care | 2017 |
| Meds on Time Ltd | Wholesale & retail | 2024 |
| Medtech Sales Recruitment Ltd | Administrative & support | 2024 |
| Mehal Construction and Property Management Ltd | Construction | 2025 |
| Mehal Group Ltd | Construction | 2025 |
| MEK Anaesthesia Services Limited | Real estate | 2026 |
| Melfin Medical Limited | Health & social care | 2022 |