| Mini and ME and More Limited | Wholesale & retail | 2021 |
| Mini Miracles Cleaning Services Ltd | Administrative & support | 2008 |
| Minley Grove Management Company Limited | Households | 1986 |
| Minley Manor Limited | Extraterritorial | 2016 |
| Minley Nursery (Tongham) Management Company Limited | Households | 2017 |
| Mint and MOP Limited | Administrative & support | 2025 |
| Mintco Automotive Ltd | Other services | 2018 |
| Mintco Motors Limited | Wholesale & retail | 2012 |
| Mirador Solutions Consultancy Ltd | Professional & scientific | 2021 |
| Miranda Care Limited | Health & social care | 2020 |
| Mirza Ventures Limited | Extraterritorial | 2023 |
| Mission One International Limited | Administrative & support | 2022 |
| Mister MIX Ltd | Administrative & support | 2017 |
| Misura Geospatial Limited | Administrative & support | 2024 |
| Mixten Services Ltd | Professional & scientific | 2011 |
| MJ Hunter Limited | Wholesale & retail | 2011 |
| MJ Renewable Energy Ltd | Administrative & support | 2019 |
| MJ Telcoms Ltd | Construction | 2025 |
| Mjrogers Group Ltd | Wholesale & retail | 2026 |
| MK Database Solutions Limited | Information & communication | 2012 |
| MK Marketing Specialists Limited | Information & communication | 2018 |
| MK Supermarket Ltd | Transport & logistics | 2022 |
| MK Supermarket Store Ltd | Wholesale & retail | 2023 |
| MKA Associates Limited | Professional & scientific | 2013 |
| MKH Electrical Installations Limited | Construction | 2022 |
| Mkkb Ltd | Administrative & support | 2022 |
| Mkls Consultancy Ltd | Professional & scientific | 2026 |
| ML & JG Consulting Services Limited | Professional & scientific | 2026 |
| MLA Inc Limited | Other services | 2019 |
| MMA Code Solutions Limited | Information & communication | 2025 |
| MMB Associate Ltd | Wholesale & retail | 2024 |
| MME Advisory Services Limited | Professional & scientific | 2025 |
| MMG Medical Limited | Wholesale & retail | 2020 |
| Mmglobalmetals Ltd | Wholesale & retail | 2026 |
| MNJ Clinical Imaging Ltd | Wholesale & retail | 2026 |
| MNK Roberts Consulting Limited | Administrative & support | 2015 |
| Moash Ltd | Information & communication | 2026 |
| Mobile Cctv & Security Services Ltd | Extraterritorial | 2003 |
| Mobile Cctv Ltd | Administrative & support | 2000 |
| Mobius Environmental Limited | Water & waste | 2009 |
| Moda B Cuts Limited | Other services | 2025 |
| Model Project (UK) Ltd | Health & social care | 2007 |
| Modern Skin Limited | Other services | 2025 |
| Modgil Study Circle LLP | | 2024 |
| Moginie James Financial Services Ltd | Extraterritorial | 2014 |
| Moginie James Limited | Extraterritorial | 2003 |
| Momi V Ltd | Hospitality | 2020 |
| Monad Precision Engineering Limited | Professional & scientific | 1975 |
| Mondragon Limited | Real estate | 2012 |
| Monks Vaughan Limited | Information & communication | 2005 |
| Monolith Global Ltd | Wholesale & retail | 2019 |
| Montel Title Limited | Professional & scientific | 1996 |
| Montgomery Farm Limited | Agriculture & fishing | 1997 |
| Moonlight 658 Limited | Hospitality | 2025 |
| Moonlight Kitchen Limited | Hospitality | 2019 |
| Mops & Buckets Ltd | Administrative & support | 2026 |
| Moray Projects Limited | Professional & scientific | 2024 |
| Moreco Group Limited | Wholesale & retail | 2021 |
| Moreco Holdco Limited | Wholesale & retail | 2023 |
| Moreco Property Limited | Real estate | 2021 |
| Morekare Services Ltd | Information & communication | 2022 |
| Moreton Place (Chertsey) Management Company Limited | Households | 1997 |
| Morgan-Brown Consulting Ltd | Professional & scientific | 2026 |
| Mortgage & Insurance Bureau Limited | Extraterritorial | 1997 |
| Mortimer Nannies Festival Babysitting Limited | Health & social care | 2017 |
| Moscas River Ltd | Financial services | 2018 |
| Moss Rocks Jewellery Ltd | Manufacturing | 2019 |
| Mostyn Court Freehold Limited | Households | 1982 |
| Motion Mortgages and Protection LLP | | 2026 |
| Moto Prestige Limited | Extraterritorial | 2009 |
| Motofix (Aldershot) Limited | Extraterritorial | 2001 |
| Motofix (Cirencester) Limited | Extraterritorial | 2010 |
| Motofix (Exeter) Limited | Wholesale & retail | 2023 |
| Motofix (High Wycombe) Limited | Extraterritorial | 1996 |
| Motofix (Northampton) Limited | Extraterritorial | 1977 |
| Motofix (Oxford) Limited | Extraterritorial | 2010 |
| Motofix (Swindon) Limited | Extraterritorial | 2010 |
| Motofix (Yeovil) Limited | Wholesale & retail | 2023 |
| Motofix Accident Repair Centres Limited | Wholesale & retail | 1998 |
| Motofix Group Limited | Extraterritorial | 2015 |
| Motofix Limited | Extraterritorial | 2002 |
| Motofix Prestige Limited | Wholesale & retail | 2018 |
| Motofix Prestige Paint & Body Limited | Extraterritorial | 2018 |
| MOTOFIX2GO Limited | Wholesale & retail | 2023 |
| Motor Mates Parts Centre | | 1994 |
| Motormech Guildford Limited | Wholesale & retail | 2005 |
| Mountside Place Residents Company Limited | Households | 1998 |
| Mousike Entertainment Ltd | Information & communication | 2025 |
| Movello Ltd | Real estate | 2025 |
| Movina Ltd | Health & social care | 2025 |
| Moyo Consultancy Ltd | Manufacturing | 2022 |
| Mozzimo Limited | Information & communication | 2026 |
| MP Film Consultants Ltd | Information & communication | 2017 |
| MP Trimz Ltd | Manufacturing | 2024 |
| Mpala Beginnings Limited | Health & social care | 2014 |
| MPI Tech Limited | Information & communication | 1998 |
| Mppway Ltd | Construction | 2017 |
| MR COD (Camberley) Ltd | Hospitality | 2013 |
| MR FIX Limited | Administrative & support | 2017 |
| MR Peri Peri Ltd | Hospitality | 2025 |