| Medi-Kal Expert Alliance Ltd | Administrative & support | 2022 |
| Media Transport and Services Limited | Other services | 2014 |
| Mediaeval Baebes Limited | Arts & recreation | 1997 |
| Medialogy Broadcast Limited | Administrative & support | 2019 |
| Medical Alternatives Limited | Health & social care | 2001 |
| Medicalc Financial Services Ltd | Professional & scientific | 2026 |
| Medidac Limited | Administrative & support | 2007 |
| Medsafe Clinical Ltd | Professional & scientific | 2026 |
| Medusa Corporate Services Ltd | Administrative & support | 2016 |
| Meeja Limited | Administrative & support | 2002 |
| Mega Tiles Ltd | Administrative & support | 2023 |
| Megaserve Limited | Construction | 2012 |
| Mehmets Kitchen Ltd | Hospitality | 2025 |
| Melanie Walters Pharma Limited | Administrative & support | 2012 |
| Melankolic Recordings Limited | Information & communication | 2016 |
| Melbury Construction Consultants Ltd. | Professional & scientific | 2009 |
| Melcombe News Limited | Wholesale & retail | 2003 |
| Meliorate Institute Education and Training Ltd | Professional & scientific | 1974 |
| Melo & Costa Limited | Information & communication | 2025 |
| Melodi Horne Limited | Wholesale & retail | 2012 |
| Melodybright Limited | Real estate | 1995 |
| Melrose Property Management Ltd | Real estate | 2026 |
| Melvin Roofing and Building Ltd | Construction | 2025 |
| Memocan Ltd | Hospitality | 2025 |
| Menik Investment Limited | Real estate | 2013 |
| Mentenance&Cleaning Service Ltd | Construction | 2026 |
| Meraki Property Ltd | Real estate | 2016 |
| Mercury Energy Limited | Information & communication | 1997 |
| Merry Oak Limited | Real estate | 2021 |
| Mesla Limited | Information & communication | 2017 |
| Message Property Investments Limited | Real estate | 1997 |
| Mesubim Limited | Professional & scientific | 2015 |
| Metal Music Bookings & Management Ltd | Arts & recreation | 2009 |
| Metamorphosis Investments Limited | Real estate | 2012 |
| Metis Build Limited | Construction | 2018 |
| Metis Homes (Millers Brook) Limited | Extraterritorial | 2011 |
| Metis Homes Limited | Construction | 2007 |
| Meypayatu Limited | Education | 2014 |
| MF Maintenance London Limited | Construction | 2025 |
| MGR Sparx Ltd | Construction | 2006 |
| Mgyconsult Ltd | Professional & scientific | 2017 |
| MH SAP Consulting Ltd | Information & communication | 2017 |
| Mhtb Properties Ltd | Real estate | 2025 |
| MI Agent London Limited | Administrative & support | 2015 |
| MI Music Academy Limited | Other services | 2023 |
| MI365 Limited | Administrative & support | 2016 |
| MIA Casa Limited | Real estate | 2023 |
| Michael Alexandros Properties Limited | Real estate | 2026 |
| Michael Evans Decorating Contractors Limited | Construction | 2003 |
| Michael Filiou Consulting Ltd | Administrative & support | 2016 |
| Michael Filiou Holdings Ltd | Administrative & support | 2017 |
| Michael Filiou Limited | Professional & scientific | 2001 |
| Michael Gerson Limited | Extraterritorial | 2008 |
| Michael Gerson Relocation Limited | Extraterritorial | 2008 |
| Micromobility Innovation Ltd | Manufacturing | 2021 |
| Middeys (Potters Bar) Ltd | Hospitality | 2024 |
| Midlands Investments 1 LLP | | 2023 |
| Midway Holdings Ltd | Real estate | 2017 |
| Midway Insurance Services Limited | Financial services | 1978 |
| MIG Lock Limited | Professional & scientific | 2017 |
| Mikaela Filio Ltd | Administrative & support | 2017 |
| Mikaela Group Ltd | Administrative & support | 2017 |
| Mikaela Ltd | Administrative & support | 2017 |
| Mila Fashion (London) Limited | Wholesale & retail | 2017 |
| Milana Events Ltd | Wholesale & retail | 2013 |
| Mile Deep Solutions Ltd | Administrative & support | 2023 |
| Mill Square Management Limited | Households | 1987 |
| Millan Estates Limited | Extraterritorial | 2001 |
| Millbell Services Ltd | Professional & scientific | 2020 |
| Millbrook Management Ltd | Real estate | 2025 |
| Millcraft Ltd | Construction | 2008 |
| Miller Investments Ltd | Administrative & support | 2026 |
| Miller Saptech Ltd | Information & communication | 2019 |
| Millstream Management Co. Limited | Households | 1988 |
| Milly's Patisserie Ltd | Manufacturing | 2020 |
| Miltonia Health Science Ltd | Wholesale & retail | 2009 |
| Mima Investments Limited | Real estate | 2016 |
| Mimar Investment Ltd | Administrative & support | 2012 |
| Mimelma Limited | Professional & scientific | 1993 |
| Mimi Brown Design Limited | Professional & scientific | 2014 |
| Mimms Properties Ltd | Real estate | 2020 |
| Mina an Limited | Real estate | 2011 |
| Mindful Montessori Ltd | Education | 2023 |
| Minehead Old Town Hall Investments Limited | Construction | 2015 |
| Mini Spares Centre (Midlands) Ltd. | Extraterritorial | 1999 |
| Mini Spares Centre Holdings Limited | Professional & scientific | 2001 |
| Mini Spares Centre Limited | Wholesale & retail | 1977 |
| Mini Spares Limited | Financial services | 1995 |
| Mini Spares Midlands Limited | Extraterritorial | 1996 |
| Minikin Media Limited | Information & communication | 2008 |
| Minnie Investments Limited | Real estate | 2021 |
| Minta Associates Limited | Professional & scientific | 2016 |
| Minx Productions Limited | Information & communication | 2018 |
| Miol LLP | | 2025 |
| MIR PAC Ltd | Manufacturing | 2021 |
| MIR Packaging Ltd | Manufacturing | 2010 |
| Mira Properties Limited | Real estate | 2020 |
| Mishellis Properties Limited | Administrative & support | 2001 |
| Miss Fit Wear Limited | Other services | 2019 |
| Misuenos Limited | Manufacturing | 2014 |