| Marian & Mirela Ltd | Construction | 2025 |
| Marian Composites Ltd | Manufacturing | 2023 |
| Marian Disagila Ltd | Construction | 2022 |
| Mariekit & Co Ltd | Other services | 2025 |
| Marigold PTS Limited | Real estate | 2016 |
| Marika Property Ltd | Real estate | 2024 |
| Marikem Creatives Ltd | Information & communication | 2021 |
| Marilla Garland Property Management Limited | Real estate | 2007 |
| Marina-Tonev Ltd | Transport & logistics | 2019 |
| Marinnovac UK Limited | Professional & scientific | 2019 |
| Mario Kobat - Aerospace Structures Technician Ltd | Manufacturing | 2026 |
| Mario&Kev Ltd | Transport & logistics | 2018 |
| Mariogomuvets Ltd | Professional & scientific | 2025 |
| Marios Avionics Ltd | Manufacturing | 2024 |
| Maritec Engineering and Services Limited | Wholesale & retail | 2022 |
| Maritime Recruitment Company Ltd | Professional & scientific | 2020 |
| Marium Travel &Tours Ltd | Transport & logistics | 2013 |
| Marius Klusas Yacht Building Ltd | Manufacturing | 2019 |
| Mark & Owen Limited | Other services | 2026 |
| Mark Cross Limited | Transport & logistics | 2000 |
| Mark Darling Limited | Real estate | 1997 |
| Mark DE Rond Limited | Professional & scientific | 2016 |
| Mark Hough Ltd | Professional & scientific | 2008 |
| Mark Lunn Associates Limited | Professional & scientific | 2015 |
| Mark Rogers Advisory Ltd | Information & communication | 2025 |
| Mark Stalham Potato Consultancy Ltd | Agriculture & fishing | 2020 |
| Marken Property Ltd | Construction | 2019 |
| Marker Groupe Ltd | Information & communication | 2022 |
| Market Advantage Group Ltd. | Professional & scientific | 2015 |
| Market Logic Consulting Limited | Information & communication | 2025 |
| Market Rise Management Limited | Households | 2002 |
| Market Square Cafe Ltd | Hospitality | 2017 |
| Market Square Consulting Limited | Professional & scientific | 2025 |
| Market Square Potton Limited | Professional & scientific | 2022 |
| Market Systems Limited | Information & communication | 2010 |
| Market Warsop (Stonebridge Lane) Management Company Limited | Households | 2022 |
| Marketcam Ltd | Hospitality | 2018 |
| Marketing Sense Limited | Professional & scientific | 2001 |
| Marketing Sparkle Limited | Professional & scientific | 2005 |
| Marketing Zone Limited | Professional & scientific | 1997 |
| Markham Private Clients Ltd | Financial services | 2012 |
| Marks PVT Ltd | Real estate | 2024 |
| Marksy Labs Ltd | Information & communication | 2025 |
| Markwell Consulting Ltd | Public administration | 2024 |
| Marlborough Grove Estate Management Company Limited | Households | 2016 |
| Marleigh Phase 2 Block Management Company Limited | Real estate | 2021 |
| Marleigh Square Ltd | Hospitality | 2021 |
| Marlow Consulting Services Ltd | Professional & scientific | 2024 |
| Marlowe Sales Partners Ltd | Wholesale & retail | 2026 |
| Marquees 4 Locations Ltd. | Administrative & support | 2022 |
| Marriott & Associates | | 1987 |
| Marriott Coaching Ltd | Professional & scientific | 2019 |
| Marrow&Gold Ltd | Real estate | 2025 |
| Marryat Investments Limited | Financial services | 2000 |
| Marsh International Moving Ltd. | Transport & logistics | 2000 |
| Marsh International Relocation Ltd. | Transport & logistics | 2002 |
| Marshal Books Ltd | Information & communication | 2026 |
| Marshall ADG Ltd | Financial services | 2017 |
| Marshall Black Design Ltd | Manufacturing | 2016 |
| Marshall Cambridge Airport Ltd | Transport & logistics | 2023 |
| Marshall Group Properties Limited | Real estate | 1986 |
| Marshall Land Systems Ltd | Manufacturing | 1991 |
| Marshall Middle East Limited | Administrative & support | 2014 |
| Marshall of Cambridge (Airport Properties) Limited | Extraterritorial | 2014 |
| Marshall of Cambridge (Engineering) Limited | Extraterritorial | 1968 |
| Marshall of Cambridge (Holdings) Limited | Professional & scientific | 1986 |
| Marshall of Cambridge Aerospace Limited | Manufacturing | 1930 |
| Marshall Road Apartments Limited | Households | 2014 |
| Marshall Specialist Vehicles Ltd | Manufacturing | 2006 |
| Marshall Systems UK Holdco Ltd | Financial services | 2026 |
| Marshalls Fisheries Consultant Ltd | Agriculture & fishing | 2017 |
| Marshalls Lettings Limited | Real estate | 2009 |
| Marstan BDB LLP | | 2009 |
| Martels Management Limited | Real estate | 2020 |
| Martha and Moose Limited | Manufacturing | 2020 |
| Martin James Limited | Professional & scientific | 1997 |
| Martin V. Sewell Ltd | Professional & scientific | 2018 |
| Martina 8 Ltd | Manufacturing | 2024 |
| Martindale Construction Limited | Construction | 2025 |
| Martingale House Ltd | Information & communication | 2016 |
| Martkeen Ltd | Extraterritorial | 2022 |
| Martlet Capital Directors Limited | Financial services | 2022 |
| Martlet Capital Limited | Financial services | 2021 |
| Martomola Ltd | Construction | 2025 |
| Martyn Leeks Limited | Construction | 2006 |
| Maruti Supermarket Limited | Wholesale & retail | 2025 |
| Marva Ltd | Manufacturing | 2026 |
| Marvell Limited | Arts & recreation | 2003 |
| Mary Beard Publications Limited | Information & communication | 2010 |
| Maryam Tanwir Ltd | Education | 2023 |
| Marycon Limited | Professional & scientific | 2020 |
| Marylebone International Limited | Real estate | 2017 |
| MAS International Trade Ltd | Wholesale & retail | 2026 |
| MAS Residential Limited | Real estate | 2021 |
| Masala LAB Limited | Hospitality | 2026 |
| Masau Limited | Information & communication | 2012 |
| Masindi Group Holdings Limited | Financial services | 2021 |
| Masood & Johnson Limited | Real estate | 2019 |
| Masoud Trade Co., Limited | Extraterritorial | 2025 |
| Mass Composites Ltd | Manufacturing | 2019 |