| Malik's Homes Ltd | Real estate | 2019 |
| Malikoski Construction Ltd | Construction | 2025 |
| Malisho Ltd | Real estate | 2019 |
| Mallards & Grebe Ltd | Real estate | 2012 |
| Malone Services Ltd | Professional & scientific | 2025 |
| Malpas Road Management Company Limited | Households | 2018 |
| Malpp Limited | Professional & scientific | 2009 |
| Malta Enterprise Limited | Hospitality | 2017 |
| Mamma MIA Summertown Limited | Hospitality | 2020 |
| Mamma's Vegetarian Kitchen Ltd | Hospitality | 2024 |
| Mamre Management Services Limited | Real estate | 2013 |
| MAN and YAM Holdings Limited | Hospitality | 2025 |
| MAN Catering Ltd | Hospitality | 2019 |
| MAN Clayton Partners Ltd | Professional & scientific | 2021 |
| MAN Grill Ltd | Hospitality | 2025 |
| Managed Learning Associates Limited | Professional & scientific | 2013 |
| Management Books 2000 Limited | Information & communication | 1993 |
| Management Success Investments Ltd | Real estate | 2025 |
| Manakram Ltd | Wholesale & retail | 2026 |
| Maneeza's Collection Ltd | Wholesale & retail | 2023 |
| Mangione Orange Limited | Wholesale & retail | 2025 |
| Manhire Associates Building Technology Limited | Professional & scientific | 2004 |
| Manhire Associates Geo-Environmental Limited | Construction | 2006 |
| Manhire Associates Limited | Construction | 1999 |
| Mani Design & Build Ltd | Construction | 2019 |
| Mani Estate Development Ltd | Real estate | 2026 |
| Maniar & Company Limited | Professional & scientific | 2011 |
| Mannayo Ltd | Hospitality | 2022 |
| Manners-Bell Technical Consulting Limited | Professional & scientific | 2026 |
| Manningham Lane Management Ltd | Real estate | 2020 |
| Manolo Steel Fabrication Welding Ltd | Manufacturing | 2016 |
| Manor Farm Henton Management Company Limited | Households | 2024 |
| Manor House Stoves Limited | Administrative & support | 2010 |
| Manor Investment (Oxford) Ltd | Real estate | 2017 |
| Manor Investment Advisors Ltd | Professional & scientific | 2014 |
| Manor Nottingham Limited | Real estate | 2005 |
| Mansfield College Developments Limited | Construction | 2012 |
| Manshift Recruitment Ltd | Administrative & support | 2025 |
| Mantock Services Limited | Arts & recreation | 2020 |
| Manulink Ltd | Information & communication | 2025 |
| Manx Welshpool Ltd | Real estate | 2011 |
| Manypaws Ltd | Other services | 2021 |
| Manzr Ltd | Administrative & support | 2025 |
| Maple (192) Limited | Administrative & support | 2003 |
| Maple Court (Kidlington Oxford) Management Co Limited | Households | 2001 |
| Maple Croft Developments Ltd | Construction | 2024 |
| Maple Croft Living Ltd | Real estate | 2024 |
| Mappinglab Limited | Professional & scientific | 2018 |
| MAQ Progressive Ltd | Other services | 2018 |
| Maral Properties Ltd | Real estate | 2025 |
| Marbleleaf Ltd | Real estate | 2015 |
| Marc Burca & Company Limited | Arts & recreation | 2012 |
| Marc Fitch Fund | Education | 1956 |
| Marcelino Perez Ltd | Construction | 2025 |
| Marco Palumbo Consulting Ltd | Professional & scientific | 2024 |
| Marcus Stobart Construction&Groundwork Limited | Construction | 2012 |
| Marfin (Oxford) Limited | Health & social care | 2009 |
| Marga Management Limited | Professional & scientific | 2009 |
| Marhonella Limited | Wholesale & retail | 2021 |
| Maria Alcantara Ltd | Extraterritorial | 2024 |
| Maria DE Fatima Peixoto Alcantara Ltd | Extraterritorial | 2024 |
| Mariam Creations. Limited | Wholesale & retail | 2016 |
| Marin Marinov Ltd | Other services | 2012 |
| Marion COX HR Consulting Limited | Professional & scientific | 2010 |
| Marios Pizzeria Trattoria Italiana Limited | Hospitality | 2016 |
| Mark Archer Building Services Ltd | Construction | 2012 |
| Mark Bassett Limited | Professional & scientific | 2009 |
| Mark Ellis Education Consultancy Ltd | Education | 2021 |
| Mark Ellis Interiors Limited | Construction | 2014 |
| Mark Lovelace Limited | Construction | 2001 |
| Mark Newby Associates Limited | Information & communication | 2017 |
| Mark Purcell Limited | Wholesale & retail | 2003 |
| Mark Sheehan Ethics Consulting Limited | Professional & scientific | 2024 |
| Mark Thomas Medical Limited | Professional & scientific | 2018 |
| Market Analysis Limited | Professional & scientific | 1998 |
| Marketing Communication Limited | Real estate | 1970 |
| Markinent Limited | Education | 2025 |
| Marlborough Mews Leaseholds Management Limited | Households | 1992 |
| Marlborough Resources Limited | Professional & scientific | 2016 |
| Marleywood Property Investments Ltd | Real estate | 2001 |
| Maroc Trading Limited | Wholesale & retail | 2010 |
| Marquardt U.K. Limited | Wholesale & retail | 2007 |
| Marram Dune Ltd | Real estate | 2022 |
| Marriott Smith Limited | Other services | 2006 |
| Marsden Bioinformatics Limited | Professional & scientific | 2018 |
| Marsden Health Ltd | Other services | 2024 |
| Marseclips Ltd | Water & waste | 2024 |
| Marshall Cafe Limited | Hospitality | 2025 |
| Marshall Consulting Services Limited | Information & communication | 2021 |
| Marshall Driveways & Roofing Ltd | Construction | 2024 |
| Marshall Food Market Limited | Wholesale & retail | 2025 |
| Marshalltown U.S.A. Ltd | Wholesale & retail | 2025 |
| Marshes CPA LLP | | 2008 |
| Marshes LLP | | 2009 |
| Martin AV Limited | Construction | 2023 |
| Martin Meagher Electrical Limited | Construction | 2017 |
| Martin Palmer Publishing Services Limited | Information & communication | 2014 |
| Marttirreno Ltd | Wholesale & retail | 2023 |
| Martyr Consulting Limited | Professional & scientific | 2024 |
| Marvel Maker Culture & Technology Ltd | Professional & scientific | 2014 |