| Mackula Trade Limited | Administrative & support | 2013 |
| Macob Systems Limited | Real estate | 1986 |
| Macood Ltd | Manufacturing | 2025 |
| Macwood Builders Limited | Construction | 1988 |
| Macyleigh Limited | Arts & recreation | 2016 |
| MAD Dog Trading Limited | Wholesale & retail | 2015 |
| MAD M.A.C. Group Ltd | Information & communication | 2019 |
| MAD MAX Limited | Extraterritorial | 2005 |
| MAD Women Management Limited | Professional & scientific | 2021 |
| Maddox Nain Electrical Ltd | Construction | 2015 |
| Madeleine Lodge (Management) Limited | Households | 1988 |
| Mader Ltd | Construction | 2014 |
| Madisons Recruitment Ltd | Administrative & support | 2015 |
| Madrian Ltd | Construction | 2018 |
| Madrid Properties Limited | Real estate | 2024 |
| Maelor Property Holdings Ltd | Real estate | 2026 |
| Magdala Salcombe Limited | Real estate | 2002 |
| Magic Drinks Limited | Wholesale & retail | 2020 |
| Magic Spanner Media Ltd | Administrative & support | 2023 |
| Magical Masala Bites Ltd | Hospitality | 2024 |
| Magnasoft Europe Ltd | Administrative & support | 2004 |
| Magnificent! Limited | Information & communication | 2002 |
| Magnolia Investments Limited | Arts & recreation | 1996 |
| Magpie Trustees (London) Limited | Professional & scientific | 2009 |
| Magwood Environmental Services Limited | Construction | 2015 |
| Magwood Property Investments Limited | Real estate | 2014 |
| Magwood Truck & Plant Services Limited | Other services | 2002 |
| MAH Cafe Express Ltd | Hospitality | 2023 |
| Mahanari Ltd | Health & social care | 2022 |
| Mahen Jhugroo Ltd | Health & social care | 2021 |
| Mahonia Invest Ltd | Real estate | 2023 |
| MAI Property Rental Ltd | Real estate | 2026 |
| Maida Property Ltd | Real estate | 2024 |
| Maidapharm Ltd | Wholesale & retail | 2025 |
| Maids in London Ltd | Administrative & support | 2025 |
| Maidstone Local Express Ltd | Wholesale & retail | 2025 |
| Maintenance Inclusive Limited | Administrative & support | 2020 |
| Mainz Ltd | Health & social care | 2018 |
| Maishugo Limited | Extraterritorial | 2017 |
| Maison Meow Limited | Professional & scientific | 2025 |
| Maison Private Finance Ltd | Financial services | 2020 |
| Majani Groundworks Ltd | Construction | 2003 |
| Majestic Textiles Limited | Manufacturing | 1996 |
| Majestically Rare Limited | Administrative & support | 2023 |
| Majiktree Consulting Limited | Professional & scientific | 2014 |
| Majordeal Properties Limited | Real estate | 2004 |
| Makeajourney.Co.Uk Ltd | Administrative & support | 2016 |
| Makosv Beauty & Aesthetics Limited | Other services | 2024 |
| Malaika Noor Ltd | Other services | 2025 |
| Malanga Properties Ltd | Real estate | 2023 |
| Malar Homes Ltd | Real estate | 2020 |
| Malborough Investments Limited | Real estate | 2013 |
| Malcolm Bruce Music Ltd | Information & communication | 2024 |
| Malferd Properties Limited | Real estate | 2000 |
| Mallace Victoria Ltd | Manufacturing | 2019 |
| Malonne Ltd | Information & communication | 2022 |
| Malt Real Estate Ltd | Real estate | 2024 |
| Malus Grove Limited | Other services | 2012 |
| Malvern Court Residents Association Limited | Households | 1982 |
| MAM Olds Ltd | Financial services | 2022 |
| Mama Africa Entertainment and Events Limited | Arts & recreation | 2018 |
| Mammoth Fleet Ltd | Transport & logistics | 2025 |
| Mamo Investments Ltd | Real estate | 2023 |
| MAN & Co International Ltd | Administrative & support | 2014 |
| MAN & Co Management Consulting Ltd | Professional & scientific | 2009 |
| MAN in the Arena Design Limited | Professional & scientific | 2021 |
| Mana and Bread Limited | Professional & scientific | 2016 |
| Manas Life Studio Limited | Administrative & support | 2018 |
| Manas Property Investments Ltd | Real estate | 2025 |
| Manchester Trading 3GO Limited | Hospitality | 2025 |
| Mancone Edgware Ltd | Hospitality | 2018 |
| Mancone Limited | Hospitality | 2011 |
| Mande London Ltd | Hospitality | 2024 |
| Mandres Property Management Ltd | Real estate | 2024 |
| Manerg Limited | Construction | 2022 |
| Manergi Tech Solutions Ltd | Wholesale & retail | 2022 |
| Manetti Young Limited | Real estate | 2009 |
| Mango Moon Consultancy Ltd | Information & communication | 2014 |
| Mango Prop Co. Limited | Real estate | 2026 |
| Mangott Ltd | Construction | 2024 |
| Manifest Coffee Limited | Hospitality | 2025 |
| Manifest New Business Limited | Professional & scientific | 2015 |
| Manik Management Limited | Professional & scientific | 2025 |
| Manju & Co. Ltd. | Information & communication | 2013 |
| Mann Consultants Limited | Administrative & support | 2018 |
| Manon Design LLP | | 2014 |
| Manops Consulting Ltd | Administrative & support | 2023 |
| Manor Contractors Limited | Construction | 2021 |
| Manor Court Freehold Limited | Real estate | 2014 |
| Manor Hall Management Company Ltd | Administrative & support | 2018 |
| Manor House (London) Limited | Real estate | 2013 |
| Manor Newbuild Limited | Construction | 2025 |
| Manor Studios Ltd | Real estate | 2014 |
| Manorwest Limited | Real estate | 1985 |
| Mansarda Ltd | Administrative & support | 2016 |
| Mansio Holdings Ltd | Real estate | 2020 |
| Mansio Homes Ltd | Real estate | 2020 |
| Mansoor Holdings Limited | Real estate | 2017 |
| Mantinea Clothing Ltd | Wholesale & retail | 2024 |
| Mantis Avicenna Limited | Other services | 2020 |