| Maleeha Beauty Ltd | Other services | 2021 |
| Mamby Services Limited | Construction | 2025 |
| Mammoplasty Ltd | Health & social care | 2017 |
| Managed IT Services Limited | Information & communication | 2011 |
| Manderley Press Ltd | Information & communication | 2021 |
| Mani Property Ltd | Real estate | 2025 |
| Manic Management Limited | Real estate | 2022 |
| Mann O Salwa Limited | Hospitality | 2023 |
| Manor Road (West HAM) Management Limited | Households | 1994 |
| Mansee Ltd | Real estate | 2022 |
| Manura Consultancy Ltd | Information & communication | 2013 |
| MAP Capital Investments Limited | Real estate | 2016 |
| Maria Bazdar Property Investments Ltd | Real estate | 2022 |
| Maria Caruso Couture Ltd | Wholesale & retail | 2019 |
| Mario Construction Ltd | Construction | 2011 |
| Maritime Horizons Ltd | Professional & scientific | 2008 |
| Mark Ferris Limited | Information & communication | 2018 |
| Mark Fisher Carshalton Limited | Wholesale & retail | 2007 |
| Mark Hansford Consulting Ltd | Professional & scientific | 2025 |
| Martin Building Services Limited | Construction | 2025 |
| Marvi Decor Ltd | Construction | 2020 |
| Maryam Kitchen Ltd | Hospitality | 2023 |
| Masa Property Limited | Real estate | 2026 |
| Masha Entertainment Ltd | Professional & scientific | 2025 |
| Maskan Global Ltd | Real estate | 2024 |
| Maskell’S Ornate Plasterwork Ltd | Construction | 2021 |
| Masters of Change Management Ltd | Information & communication | 2021 |
| Mastersmind Ltd | Education | 2024 |
| Mathieson Garven Associates Limited | Professional & scientific | 2016 |
| Mathura Property Ltd | Real estate | 2019 |
| Matkas Ventures Trading Ltd | Wholesale & retail | 2025 |
| Matsure Consulting Limited | Information & communication | 2025 |
| Matthew S Martin ADR Limited | Administrative & support | 2025 |
| Maudho & Co Ltd | Extraterritorial | 2024 |
| MAV Management Ltd | Construction | 2022 |
| Maxtone Property Company Limited | Real estate | 2021 |
| Maxus Construction Ltd | Construction | 2025 |
| Mayfair Associates London Ltd | Professional & scientific | 2017 |
| MB & TK Property Limited | Real estate | 2020 |
| MB Property Consultancy Ltd | Construction | 2020 |
| MC Lazaro Limited | Health & social care | 2013 |
| Mccue Franklin Accountants Limited | Professional & scientific | 2017 |
| MD Solecare Limited | Administrative & support | 2013 |
| MDS AI Ltd | Administrative & support | 2026 |
| Meadvale Property Limited | Real estate | 2015 |
| Meddraig Medical Services Ltd | Health & social care | 2024 |
| Medel Services Limited | Administrative & support | 2021 |
| Media Insight Limited | Administrative & support | 2024 |
| Mediantone Ltd | Administrative & support | 2017 |
| Meedial Ltd | Information & communication | 2024 |
| Meera Management Services Ltd | Real estate | 2022 |
| Megpol Service Ltd | Construction | 2019 |
| MEL House Staging Studios Ltd | Professional & scientific | 2026 |
| Melcia Services Limited | Hospitality | 2025 |
| Mems Catering Ltd | Hospitality | 2025 |
| Mesh Investments Ltd | Real estate | 2017 |
| Metro Scooters Ltd | Wholesale & retail | 2024 |
| Mfahh Associates Limited | Real estate | 2020 |
| Mfzp Limited | Health & social care | 2015 |
| MG Scaffolding Solutions Ltd | Construction | 2025 |
| MGF Design Limited | Professional & scientific | 2008 |
| MHP Surrey Ltd | Construction | 2015 |
| MI Casa, TU Casa Ltd | Real estate | 2018 |
| Miao Consulting Ltd | Information & communication | 2010 |
| MIC Maintenance Limited | Households | 2025 |
| Michal Pawelec Limited | Construction | 2023 |
| Micklefield Limited | Construction | 1953 |
| Micona Construction Ltd | Construction | 2026 |
| Micuchunas Ltd | Transport & logistics | 2010 |
| Midas Art Ltd | Wholesale & retail | 2025 |
| Midas Fashion Company Limited | Wholesale & retail | 2014 |
| MILLENNIUM2017 Limited | Transport & logistics | 2017 |
| Millers Kitchen Limited | Hospitality | 2026 |
| Mind Resilience Limited | Health & social care | 2016 |
| Mindfrxme Limited | Information & communication | 2024 |
| Mindful Business Consulting Ltd | Information & communication | 2017 |
| Mindful Medlab Ltd | Professional & scientific | 2024 |
| Mindmaps Coaching Limited | Information & communication | 2025 |
| Mindmux C.I.C. | Information & communication | 2024 |
| Mirasoft Holdings Ltd | Information & communication | 2024 |
| Mirb Traders Ltd | Transport & logistics | 2022 |
| Miribiri One Ltd | Real estate | 2024 |
| Missiox Limited | Wholesale & retail | 2025 |
| Mitcham & Carshalton Rugby Union Football Club | Arts & recreation | 2021 |
| Mitchley Developments (AP) Limited | Construction | 2026 |
| Mitchley Developments (Margate Road) Limited | Real estate | 2022 |
| Mitchley Developments (WH) Limited | Construction | 2024 |
| Mithraam Ltd | Real estate | 2023 |
| MJ Deca Ltd | Construction | 2023 |
| MK Builders Decorators Limited | Construction | 2018 |
| MK Building & Recycling Ltd | Construction | 2020 |
| MK1 Consultancy Ltd | Professional & scientific | 2024 |
| Mkis Limited | Construction | 2009 |
| MKM General Building Ltd | Construction | 2016 |
| ML Habitat Properties Ltd | Real estate | 2020 |
| MLE Systems Ltd | Information & communication | 2011 |
| MM Building Services Ltd | Construction | 2014 |
| Moaz Solutions Ltd | Construction | 2023 |
| Mofaith Group Ltd | Construction | 2025 |
| Mojo Grube Ltd | Wholesale & retail | 2020 |