| Market Bosworth Farm Sales Limited | Wholesale & retail | 2002 |
| Marketing Information Systems Limited | Information & communication | 2002 |
| Marketmapr Limited | Information & communication | 2024 |
| Marks Metal Recycling Limited | Water & waste | 2013 |
| Marly's & Co Ltd | Hospitality | 2021 |
| Marquis Bill Entertainment Ltd | Information & communication | 2020 |
| Marshall Automotive Ltd. | Administrative & support | 2015 |
| Marshall Carpentry Ltd | Manufacturing | 2022 |
| Marshall James Limited | Financial services | 2007 |
| Marshward Power Transmissions Limited | Professional & scientific | 2013 |
| Marston & Co Financial Services Limited | Financial services | 2025 |
| Marsupial Limited | Wholesale & retail | 2025 |
| Martin & Aura Limited | Administrative & support | 2015 |
| Martin Gallichan Flooring Contractor Limited | Construction | 2002 |
| Masons Creative Limited | Professional & scientific | 2024 |
| Massage by Katie Ltd | Extraterritorial | 2025 |
| Massive Jones Limited | Other services | 2020 |
| Masterbuild Brickwork Contractors Limited | Construction | 2006 |
| Mastergraph Ltd | Manufacturing | 2022 |
| MAT Trading Limited | Wholesale & retail | 2017 |
| Matasuk Ltd | Wholesale & retail | 2024 |
| Matatu Global Limited | Professional & scientific | 2021 |
| Matdom Ltd | Transport & logistics | 2026 |
| Mathphys Tutoring and Coaching Ltd | Education | 2024 |
| Matresa Limited | Information & communication | 2025 |
| Matrix Computer Recruitment Limited | Administrative & support | 1999 |
| Matt Madden Photography Ltd | Professional & scientific | 2023 |
| Matter Marketing Ltd. | Professional & scientific | 2013 |
| Mattjbarbers Ltd | Other services | 2016 |
| Mattu Health Solutions Limited | Health & social care | 2008 |
| Maui Health Limited | Health & social care | 2024 |
| Maurice Johnson & Partners UK Limited | Public administration | 2024 |
| Mavis Holdings Limited | Financial services | 2025 |
| Maweswood Limited | Manufacturing | 2023 |
| Mawtec Solutions Ltd | Information & communication | 2014 |
| MAX Safeguarding Ltd | Education | 2025 |
| MAX Spencer Limited | Professional & scientific | 2014 |
| Maxair Services Limited | Wholesale & retail | 1999 |
| Maxi-Mix Dispense Systems Limited | Manufacturing | 2001 |
| Maxilux Lighting Ltd | Wholesale & retail | 1993 |
| Maxilux Systems EOT Trustees Ltd | Professional & scientific | 2024 |
| Maxilux Systems Ltd | Professional & scientific | 2018 |
| MAY3D Limited | Information & communication | 2024 |
| Maysalward UK Limited | Information & communication | 2017 |
| Maysons Properties Limited | Real estate | 2015 |
| Mazara Investors Limited | Real estate | 2023 |
| Maze Property Developments Limited | Construction | 2022 |
| MB & Associates Limited | Professional & scientific | 2014 |
| MB Farm Sales Limited | Wholesale & retail | 2025 |
| MB Management Group Ltd | Financial services | 2026 |
| MB Trading Holding Ltd | Energy | 2024 |
| Mbjlb Design Ltd | Construction | 2022 |
| MC Geoenvironmental Services Limited | Construction | 2019 |
| MC Hayes PUB Co Limited | Hospitality | 2025 |
| MC Wireless Solutions Limited | Information & communication | 2023 |
| Mccarthy Properties (Midlands) LLP | | 2024 |
| Mcdonagh Limited | Construction | 2001 |
| MCK Equipment Limited | Professional & scientific | 2009 |
| Mckenzie Delis Ventures Holdings Limited | Financial services | 2018 |
| Mckinney Haulage Liverpool Ltd | Manufacturing | 2020 |
| Mcneil Maintenance Ltd | Construction | 2022 |
| Mcpherson Rose Holdings Limited | Extraterritorial | 2023 |
| MDG Planning Ltd | Professional & scientific | 2023 |
| Mdias Ltd. | Real estate | 2023 |
| MDM Plumbing & Heating (Midlands) Ltd | Construction | 2023 |
| MDN Pilates Ltd | Arts & recreation | 2025 |
| MDN Social Limited | Wholesale & retail | 2026 |
| MDV Leamington Limited | Professional & scientific | 2024 |
| MDV Salford 1 Limited | Real estate | 2018 |
| MEA Vita Ltd | Wholesale & retail | 2023 |
| Meadow 1963 Limited | Extraterritorial | 2013 |
| Meadow Cars Limited | Wholesale & retail | 2014 |
| Meadows Group Limited | Professional & scientific | 2022 |
| Meadows Mechanical Services Limited | Professional & scientific | 2022 |
| Meazza Group Ltd | Professional & scientific | 2025 |
| Mechanic Mindset Ltd | Education | 2019 |
| Mechlight Ltd | Information & communication | 2025 |
| Medblue Limited | Administrative & support | 2021 |
| Medexpress Enterprises Ltd | Wholesale & retail | 2013 |
| Medical Education Limited | Administrative & support | 2006 |
| Medical Solutions AM Ltd | Health & social care | 2026 |
| Medicine Films Ltd | Professional & scientific | 2014 |
| Medics Plus Limited | Professional & scientific | 2010 |
| Medictionary Ltd | Information & communication | 2025 |
| Meet by the Park Ltd | Real estate | 2019 |
| Mega House Ltd | Real estate | 2022 |
| Mega International Limited | Information & communication | 2000 |
| Megabox Fitness Ltd | Arts & recreation | 2020 |
| Megahub Ltd | Information & communication | 2025 |
| MEL International Systems Limited | Manufacturing | 2018 |
| Melanie Williams Limited | Administrative & support | 2012 |
| Mellior Living Ltd | Households | 2025 |
| Mellors Court Limited | Households | 1992 |
| Melrose Care Properties Ltd | Real estate | 2024 |
| Mendl Nursery Harbury Limited | Health & social care | 2013 |
| Mensarius Limited | Professional & scientific | 2005 |
| Mental Health Check in Ltd | Health & social care | 2020 |
| Mentmore Holdings Limited | Professional & scientific | 2008 |
| Mentoriq Limited | Information & communication | 2024 |
| Mentra Admissions LLP | | 2024 |