| Mifm Family Limited | Financial services | 2023 |
| Milan Services Limited | Wholesale & retail | 2005 |
| Milburga International Limited | Financial services | 1991 |
| Mileorder Limited | Real estate | 2003 |
| Milinabu Limited | Real estate | 2024 |
| Mill Heights Limited | Real estate | 2017 |
| Millbond Ltd | Financial services | 2023 |
| Millennium Energy Limited | Administrative & support | 2025 |
| Millennium EV Charging Limited | Construction | 2025 |
| MILO2 Holdings Limited | Other services | 2025 |
| Milpaarth UK Ltd | Real estate | 2015 |
| Milro Holdings Limited | Health & social care | 2026 |
| Milu Investments Limited | Real estate | 2017 |
| Minca Consulting Limited | Professional & scientific | 2017 |
| Minca Finance Limited | Construction | 2023 |
| Minca Holdings Limited | Financial services | 2023 |
| Mindglow Healthcare Ltd | Health & social care | 2023 |
| Mindglow Solutions Limited | Information & communication | 2012 |
| Minervan Ltd | Households | 2017 |
| Minicabs Hub Ltd | Transport & logistics | 2024 |
| MINIMOBILES4U.COM Ltd | Wholesale & retail | 2013 |
| Mint Renewables Limited | Manufacturing | 2024 |
| Miracle Scan Hemel Hempstead Ltd | Health & social care | 2026 |
| Miracle Scan Ltd | Health & social care | 2022 |
| Mireya IT Limited | Information & communication | 2017 |
| Miroh Ltd | Health & social care | 2026 |
| Mishran Ltd | Wholesale & retail | 2021 |
| Misra Ventures Limited | Administrative & support | 2011 |
| Mistreed Limited | Real estate | 1979 |
| Mistry Training Limited | Education | 2009 |
| Mithas Limited | Professional & scientific | 1980 |
| MJ Prep Foods Limited | Wholesale & retail | 2025 |
| MJF Sales Limited | Construction | 2016 |
| MK Utilities Ltd | Construction | 2018 |
| MLC Estates Ltd | Real estate | 2021 |
| MM Advisory Ltd | Professional & scientific | 2015 |
| MM Hotels Ltd | Real estate | 2022 |
| Mmgm Limited | Health & social care | 2007 |
| MND Assets Limited | Financial services | 2026 |
| Moderno Interiors Limited | Administrative & support | 2016 |
| Modha C N Limited | Households | 2016 |
| Modi & Modi Limited | Real estate | 2009 |
| Modi Global Limited | Professional & scientific | 2022 |
| Modi London Limited | Real estate | 2025 |
| Modisto Bespoke Tailors London Ltd | Other services | 2024 |
| MOHAMMADPROPERTY.38 Ltd | Real estate | 2025 |
| Mokumayl Limited | Real estate | 2017 |
| Monachi Ltd | Construction | 2025 |
| Moniku International Limited | Professional & scientific | 2023 |
| Monocouche Mick Limited | Construction | 2015 |
| Montague Alan Limited | Other services | 1963 |
| Montague Estates UK Limited | Real estate | 2014 |
| Monti Mart UK Ltd. | Construction | 2022 |
| Moon Education & Travel Ltd | Education | 2015 |
| Moonraker One Limited | Real estate | 2019 |
| Moonrock Insurance Ltd | Financial services | 2015 |
| Moonrock Risk Management Ltd | Professional & scientific | 2026 |
| Moorehouse Consultancy Limited | Professional & scientific | 2019 |
| Moorland Homes (Cheadle) Limited | Construction | 2012 |
| Moray Road Limited | Households | 1993 |
| Moren Garden & Landscape Studio Limited | Administrative & support | 2025 |
| Morganz Health Care Ltd | Health & social care | 2020 |
| Morka Aries Limited | Financial services | 2022 |
| Morland Grange (Northcote) Management Company Limited | Real estate | 2004 |
| Morning Star Cleaners Limited | Other services | 2018 |
| Moss Shaf Holdings Ltd | Real estate | 2022 |
| Moss-Shaf Ltd | Professional & scientific | 2003 |
| Most Valuable Plumber Ltd | Construction | 2023 |
| Mostcentre Services Limited | Other services | 1993 |
| Motif Shop Ltd | Wholesale & retail | 2023 |
| Motor Vehicle Solutions Limited | Wholesale & retail | 2020 |
| Mott Street Close Limited | Real estate | 2021 |
| Mountgold Limited | Administrative & support | 2010 |
| Mountrise Limited | Real estate | 2014 |
| Mouzam Parvez Limited | Wholesale & retail | 2019 |
| Move Wellbeing Ltd | Arts & recreation | 2020 |
| MP Investments (London) Limited | Real estate | 2020 |
| MP Perio Limited | Health & social care | 2021 |
| MP Properties (Meek) Limited | Real estate | 2018 |
| MPD Plumbing and Heating Limited | Construction | 2017 |
| MR Bond Legal Ltd | Professional & scientific | 2026 |
| MR Delivery Ltd | Transport & logistics | 2025 |
| MR Glaze Limited | Extraterritorial | 2015 |
| Mrap Estates Limited | Real estate | 2022 |
| Mrpen Limited | Professional & scientific | 2005 |
| MS Packaging Limited | Administrative & support | 2013 |
| MSR Hospitality Limited | Hospitality | 2024 |
| Mstech Limited | Information & communication | 1989 |
| Mu-Sonic Ltd | Information & communication | 2013 |
| Much Property Ltd | Real estate | 2022 |
| Mulberry Business Consultancy Limited | Administrative & support | 2010 |
| Mulsys Limited | Professional & scientific | 2003 |
| Multimedia Plus Limited | Professional & scientific | 1996 |
| Multiplex Trading Ltd | Wholesale & retail | 2023 |
| Multisilver Limited | Real estate | 1988 |
| Munasifa Limited | Real estate | 2018 |
| Munchers Ltd | Other services | 2021 |
| Munday Long & Co Limited | Professional & scientific | 2000 |
| Munday Long Accounting Services Limited | Professional & scientific | 2000 |
| Munday Long Associates Ltd | Professional & scientific | 2021 |