| Malden Express Ltd | Wholesale & retail | 2026 |
| Malden Golf Club Members Ltd | Arts & recreation | 2019 |
| Malden Motors Ltd | Wholesale & retail | 2019 |
| Malden Wanderers Limited | Arts & recreation | 1927 |
| MAM KOR Ltd | Construction | 2019 |
| Mamaya Limited | Hospitality | 2012 |
| Mandarin Bay Limited | Health & social care | 2005 |
| Mansard Holdings Ltd | Real estate | 2019 |
| Maoyiba Limited | Information & communication | 2021 |
| Maple Beauty Consultancy Ltd | Other services | 2022 |
| Marathon Construction Ltd | Construction | 2025 |
| Marathon Sports Coaching Limited | Education | 2021 |
| Marble Hill Accountants Ltd | Professional & scientific | 2017 |
| Marchiemanagement Ltd | Households | 2020 |
| Mardeshaal Limited | Real estate | 2021 |
| Margon Builders Limited | Construction | 2013 |
| Mari Cape Limited | Professional & scientific | 2009 |
| Mariammudassar Ltd | Wholesale & retail | 2026 |
| Marian Lodge Freehold Company Limited | Households | 2006 |
| Marian Lodge Management Company (Wimbledon) Limited | Households | 1997 |
| Marina Freehold Limited | Households | 2022 |
| Mario-G Building Service Ltd | Construction | 2008 |
| Mark Stevenson Consulting Limited | Professional & scientific | 2018 |
| Mars Farma Ltd | Wholesale & retail | 2022 |
| Marta ACC London Limited | Professional & scientific | 2022 |
| Martax Limited | Professional & scientific | 2013 |
| Martello Land & Properties Limited | Real estate | 2007 |
| Martham Properties Ltd | Real estate | 2023 |
| Martial Sports Management Limited | Arts & recreation | 2010 |
| Martin N Construction Ltd | Construction | 2021 |
| Martin Rhodes Made IT Ltd | Professional & scientific | 2017 |
| Martinelly Ltd | Administrative & support | 2019 |
| Masala Magic Ltd | Wholesale & retail | 2021 |
| Masigo Ltd | Hospitality | 2017 |
| Massage & Wellness Ltd | Health & social care | 2016 |
| Master Chippy Ltd | Hospitality | 2018 |
| Master WEI Holding Ltd | Financial services | 2026 |
| Masy Properties Limited | Real estate | 2021 |
| Matgol Ltd | Hospitality | 2003 |
| Mattfield Limited | Professional & scientific | 2025 |
| MAW & Milk Ltd | Manufacturing | 2024 |
| Maxandi Ltd | Real estate | 2023 |
| Maximal Concepts (UK) Limited | Professional & scientific | 2021 |
| Maximeta Limited | Real estate | 2022 |
| Maximise Solutions Ltd | Information & communication | 2021 |
| Mayam Arkitektur Limited | Professional & scientific | 2024 |
| Mayfield Management (Weybridge) Limited | Households | 2002 |
| Mayhim Ltd | Information & communication | 2023 |
| Maylux Limited | Transport & logistics | 2024 |
| Maymist Limited | Transport & logistics | 2008 |
| MAZ Solution Ltd | Real estate | 2026 |
| Maza Pizza Ltd | Hospitality | 2023 |
| Maze Estates Limited | Real estate | 2015 |
| Mazoshi Limited | Real estate | 2025 |
| MB Global Emea Ltd | Wholesale & retail | 2024 |
| MB4 Ltd | Wholesale & retail | 2017 |
| MC Tutcher Limited | Professional & scientific | 2021 |
| Mckengineering Ltd | Professional & scientific | 2011 |
| Mcloughlin Property Ltd | Real estate | 2019 |
| MCR UK Management Limited | Real estate | 2018 |
| MCS Brickwork and Plastering Ltd | Construction | 2019 |
| MD Corporation Limited | Administrative & support | 2009 |
| ME2YOU Atelier Ltd | Wholesale & retail | 2021 |
| Mead Electrical Distributors Limited | Wholesale & retail | 2024 |
| Meaningful Vision Ltd | Information & communication | 2021 |
| Measured Surveying Ltd | Professional & scientific | 2014 |
| Mebridge Group Ltd | Professional & scientific | 2026 |
| MECHANICS101 Ltd | Wholesale & retail | 2014 |
| Media LAB AI Limited | Information & communication | 2018 |
| Mediam Communications Limited | Information & communication | 1998 |
| Medicto Ltd | Information & communication | 2016 |
| Megaa Store Ltd | Wholesale & retail | 2021 |
| Mehdicine Ltd | Health & social care | 2024 |
| MEI London Ltd | Professional & scientific | 2016 |
| Mekamarine Ltd | Professional & scientific | 2025 |
| Mela Anaesthetics Ltd | Health & social care | 2024 |
| Melaco Limited | Administrative & support | 2022 |
| Melmac Limited | Health & social care | 2019 |
| Melton House and Woodbury House (Wimbledon) Management Company Limited | Households | 1980 |
| Mendelian Ltd | Information & communication | 2015 |
| Menestyva Ltd | Hospitality | 2022 |
| Menetrier Investments Limited | Real estate | 1989 |
| Mercer House Consultants Limited | Professional & scientific | 2014 |
| Merchint Limited | Construction | 2010 |
| Merlinco Limited | Information & communication | 1991 |
| Merton Athletics Ltd | Education | 2023 |
| Messy Play FUN Ltd | Education | 2024 |
| MET275 Ltd | Wholesale & retail | 2025 |
| Metro DRY Cleaning Ltd | Other services | 2019 |
| Metup Limited | Professional & scientific | 2024 |
| MFS Services Limited | Administrative & support | 2018 |
| MH Family Ltd | Hospitality | 2019 |
| MHP Cleaning Ltd | Administrative & support | 2023 |
| MHZ Enterprises Limited | Administrative & support | 2013 |
| Mian Abdul Moiz Ltd | Wholesale & retail | 2025 |
| Miannewbury Company Ltd | Wholesale & retail | 2025 |
| Mica Systems Co Limited | Wholesale & retail | 2019 |
| Michael MO Ltd | Real estate | 2016 |
| Midam Restaurant Ltd | Hospitality | 2024 |
| Mier Global Ltd | Wholesale & retail | 2022 |