| M&E Invest Ltd | Financial services | 2025 |
| M&G Fire Protection Ltd | Construction | 2025 |
| M&H Education Ltd | Education | 2025 |
| M&H Pala Properties Ltd | Real estate | 2018 |
| M&J .Painting& Decoreting Ltd | Construction | 2020 |
| M&J Consultant Limited | Professional & scientific | 2014 |
| M&J Elite Services Ltd | Construction | 2023 |
| M&J Treasure Limited | Wholesale & retail | 2025 |
| M&L Construct Ltd | Construction | 2016 |
| M&M Hair and Beauty Limited | Wholesale & retail | 2012 |
| M&M Hair Studio Limited | Other services | 2023 |
| M&M London Store Limited | Wholesale & retail | 2025 |
| M&S Brothers Limited | Transport & logistics | 2008 |
| M&S Elite Ventures Limited | Wholesale & retail | 2024 |
| M&S Interior and Design Limited | Construction | 2026 |
| M&T (2020) Limited | Hospitality | 2020 |
| M&U Property Limited | Real estate | 2024 |
| M'S Chauffeurs Ltd | Wholesale & retail | 2022 |
| M-Tec Support Solutions Ltd | Real estate | 2014 |
| M. a. M Maintenance Service Limited | Construction | 2023 |
| M. a. Oriental Foods Limited | Other services | 2004 |
| M. ALI & Co UK Ltd | Professional & scientific | 2025 |
| M. Ramani Limited | Health & social care | 2022 |
| M. V. T. Limited | Wholesale & retail | 1998 |
| M. W. Mummery Roofing Limited | Construction | 2009 |
| M.&.D.(Sylvan Avenue)Management Company Limited | Real estate | 1965 |
| M.A.I.D Plumbing Limited | Construction | 2022 |
| M.A.M Extra Space Ltd | Construction | 2015 |
| M.A.S.I. Ltd | Wholesale & retail | 1997 |
| M.C.Nick Logistics Limited | Transport & logistics | 2016 |
| M.Court Holdings Limited | Financial services | 2025 |
| M.D. Phoenix Limited | Professional & scientific | 2017 |
| M.Del Engineering Limited | Construction | 2012 |
| M.G. O'Donoghue Civil Engineering Limited | Wholesale & retail | 1982 |
| M.G.A.L. Properties Limited | Real estate | 2018 |
| M.G.Assets Limited | Real estate | 1998 |
| M.J. Auctioneers and Valuers Limited | Wholesale & retail | 2022 |
| M.J.M. Pictures Ltd | Information & communication | 2007 |
| M.K. Accountancy Services Limited | Professional & scientific | 1998 |
| M.Kenny Rail Limited | Professional & scientific | 2010 |
| M.M.A. Investments Limited | Real estate | 2000 |
| M.Mena Consulting Ltd | Construction | 2023 |
| M.Nadery Ltd | Health & social care | 2025 |
| M.O.R Global C.I.C. | Health & social care | 2018 |
| M.P. Property Lettings & Sales Ltd | Construction | 2010 |
| M.R. Tiling Experts Limited | Construction | 2018 |
| M.S Skinlab Limited | Other services | 2023 |
| M.S Skyline Construction Ltd | Construction | 2020 |
| M.T.O. College | Education | 2002 |
| M.Winwood Limited | Arts & recreation | 1970 |
| M.Y Medcare Ltd | Health & social care | 2024 |
| M.Z. Plumbing & Heating Ltd | Construction | 2013 |
| M1 Liverpool Properties Ltd | Real estate | 2024 |
| M1 Trade Storage Ltd | Transport & logistics | 2021 |
| M14 Living Ltd | Real estate | 2024 |
| M14 Properties Limited | Real estate | 2017 |
| M15TRY Ltd | Professional & scientific | 2015 |
| M1S Services Limited | Administrative & support | 2025 |
| M2 (Kent) Limited | Wholesale & retail | 2010 |
| M2 Construct Ltd | Construction | 2022 |
| M2 Squared Ltd | Real estate | 2021 |
| M20 Investments Limited | Real estate | 2006 |
| M20 Properties Limited | Real estate | 2013 |
| M2M Property Services Limited | Real estate | 2004 |
| M2Z Optical Ltd | Wholesale & retail | 2012 |
| M3M Engineers Limited | Professional & scientific | 2012 |
| M3N Consultancy Ltd | Information & communication | 2015 |
| MA Building C UK Ltd | Construction | 2025 |
| MA Dentistry Limited | Health & social care | 2022 |
| MA Oriental Foods Holdings Limited | Financial services | 2021 |
| MA Plus Ltd | Administrative & support | 2025 |
| MA Securities London Limited | Administrative & support | 2016 |
| MA Trading 786 Ltd | Wholesale & retail | 2025 |
| MA4C Ltd | Professional & scientific | 2010 |
| MA8 Trading Limited | Wholesale & retail | 2020 |
| MAA Ashapuri Ltd | Hospitality | 2026 |
| MAA Bhagwati Ltd | Other services | 2025 |
| MAA Consultancy Services Limited | Wholesale & retail | 2009 |
| MAA Kamadhenu Limited | Information & communication | 2022 |
| MAA Krupa Shop Ltd | Wholesale & retail | 2024 |
| Maahi 7 Limited | Real estate | 2016 |
| Maahii London Ltd | Wholesale & retail | 2022 |
| Maan Optical Ltd | Wholesale & retail | 2019 |
| Maanara Ltd | Manufacturing | 2025 |
| Maaneet Ltd | Real estate | 2022 |
| Maanv Ltd | Real estate | 2021 |
| Maarty Properties Ltd | Real estate | 2025 |
| Mabco Constructions Ltd | Households | 2020 |
| MAC & Micro Ltd | Wholesale & retail | 2013 |
| MAC & Sons Contractors Ltd | Construction | 2019 |
| MAC Consultancy (London) Limited | Professional & scientific | 2012 |
| MAC Store LDN Ltd | Wholesale & retail | 2026 |
| Macaan Limited | Extraterritorial | 2016 |
| Macaire Solutions Ltd | Information & communication | 2024 |
| Macalvins Group Limited | Financial services | 2019 |
| Macalvins Limited | Professional & scientific | 2013 |
| Maccabi GB | Other services | 2003 |
| Maccabi GB (2021) Ltd | Administrative & support | 2021 |
| Macchiato Gifts Ltd | Wholesale & retail | 2025 |
| Macdonalds Discount Stores Ltd | Wholesale & retail | 2003 |