| M K Ginder Limited | Other services | 2011 |
| M K R LEE Limited | Real estate | 2025 |
| M K Roofing (UK) Ltd | Construction | 2015 |
| M Khan Electrical Ltd | Construction | 2019 |
| M L Chef Services Limited | Hospitality | 2015 |
| M Lawson Consulting Ltd | Information & communication | 2012 |
| M Lion Ltd | Other services | 2020 |
| M P Flooring Limited | Construction | 2003 |
| M Park Management Services Limited | Real estate | 2024 |
| M Reid Contractors Ltd | Construction | 2014 |
| M Stepan Limited | Transport & logistics | 2017 |
| M to M Solutions (UK) Private Limited | Information & communication | 2016 |
| M V Johen Ltd | Information & communication | 2015 |
| M Versani Limited | Households | 2022 |
| M W Planning Limited | Professional & scientific | 2014 |
| M Williams Data Solutions Ltd | Information & communication | 2019 |
| M Wright Events Ltd | Administrative & support | 2024 |
| M&A Wealth Ltd | Real estate | 2020 |
| M&B a Services Ltd | Professional & scientific | 2018 |
| M&D Properties Investment London Limited | Construction | 2019 |
| M&D Properties Solutions Ltd | Construction | 2016 |
| M&D Properties UK Investment Limited | Construction | 2019 |
| M&E Design Consultants Limited | Professional & scientific | 2014 |
| M&H 82 Limited | Real estate | 2022 |
| M&H 83 Ltd | Professional & scientific | 2022 |
| M&H Associates Limited | Professional & scientific | 2021 |
| M&H Building Solution Ltd. | Construction | 2018 |
| M&I T/A Jetmaid Cleaning Services Limited | Administrative & support | 2018 |
| M&J Muse Projects Ltd | Professional & scientific | 2020 |
| M&J Real Estate Limited | Real estate | 2011 |
| M&M 786 Limited | Real estate | 2024 |
| M&M Building Enterprise Ltd | Construction | 2024 |
| M&M Business Accounting Ltd | Professional & scientific | 2014 |
| M&M Cars Ltd | Wholesale & retail | 2023 |
| M&M Tech Ltd | Information & communication | 2024 |
| M&M UK Services Ltd | Real estate | 2016 |
| M&P Partners Ltd | Hospitality | 2021 |
| M&V Management Ltd | Wholesale & retail | 2018 |
| M-Cleaners Ltd | Administrative & support | 2019 |
| M-Mart Limited | Wholesale & retail | 2015 |
| M-Scube Ltd | Administrative & support | 2016 |
| M.A.D Delights Limited | Manufacturing | 2025 |
| M.A.D. Film & TV Engineering Limited | Information & communication | 2015 |
| M.A.D. Motor Spares Limited | Wholesale & retail | 2013 |
| M.A.M Electrical Services Ltd | Construction | 2023 |
| M.A.W Tiling Ltd | Construction | 2023 |
| M.B. Conquest Limited | Wholesale & retail | 1966 |
| M.B.A. Lettings & Property Management Limited | Real estate | 2005 |
| M.C. Mehta Centre for Education and Research Ltd | Professional & scientific | 2026 |
| M.C.A. DOM Care Ltd | Health & social care | 2022 |
| M.D. Driver Ltd | Transport & logistics | 2021 |
| M.I.Y Electrcial Ltd | Construction | 2019 |
| M.L.A Group Holdings Ltd | Hospitality | 2025 |
| M.L.A Security Ltd | Administrative & support | 2026 |
| M.M.A.H Investments Ltd | Real estate | 2024 |
| M.M.Team Ltd | Construction | 2008 |
| M.O.D.R. Company Ltd | Wholesale & retail | 2021 |
| M.R Partnership Limited | Professional & scientific | 1994 |
| M.T.I. (1998) Ltd | Manufacturing | 1998 |
| M.T.R. Limited | Wholesale & retail | 1981 |
| M.Walker Construction Services Ltd | Construction | 2025 |
| M.Y Techlancers Ltd | Information & communication | 2025 |
| M.Yesufu Fabrications Ltd | Manufacturing | 2022 |
| M25 Team Limited | Real estate | 2018 |
| M2M Intelligence Limited | Information & communication | 2011 |
| M2SJ Recruitment Specialist Limited | Administrative & support | 2025 |
| M3E Limited | Professional & scientific | 2014 |
| MA Financial Consultancy Limited | Professional & scientific | 2013 |
| MA Style Limited | Other services | 2021 |
| Maadhav AI Services Ltd | Information & communication | 2025 |
| Maal Trading Ltd | Wholesale & retail | 2011 |
| Maan Property Limited | Real estate | 2020 |
| Maas Services Ltd | Wholesale & retail | 2018 |
| Maavika Beauty Ltd | Other services | 2025 |
| Mabixis Ltd | Real estate | 2024 |
| Mablaw 381 Limited | Administrative & support | 1999 |
| Mablekin Limited | Agriculture & fishing | 2025 |
| MAC & Phil Ltd | Information & communication | 2014 |
| MAC Associates 2020 (UK) Limited | Administrative & support | 2020 |
| Maccabees Roofing Contractors Ltd | Construction | 2021 |
| Macduck Limited | Information & communication | 2026 |
| Mace Capital Investment Limited | Real estate | 2023 |
| Mack Digital Limited | Administrative & support | 2020 |
| Mackay Brown Partners Ltd | Professional & scientific | 2015 |
| Maclean's Accounting and Finance Services Ltd | Professional & scientific | 2014 |
| Macondo Films Limited | Information & communication | 2013 |
| Macquarie Corona Energy Holdings Limited | Professional & scientific | 2003 |
| Macs Clinic Limited | Health & social care | 2019 |
| Macs Plastic Surgery Limited | Health & social care | 2019 |
| Macvuks Consultancy Limited | Professional & scientific | 2019 |
| MAD Beauty Limited | Manufacturing | 1998 |
| MAD Cosmetics Limited | Extraterritorial | 2000 |
| Mada Capital Ltd | Real estate | 2021 |
| Madad UK (MUK) | Education | 2024 |
| Made by Dave Group Ltd | Information & communication | 2025 |
| Made to Web Ltd | Information & communication | 2019 |
| Made Unique C.I.C. | Wholesale & retail | 2019 |
| Madeja Bros Ltd | Construction | 2013 |
| Madhurams Limited | Agriculture & fishing | 2021 |
| Madhuvan MAA Properties Ltd | Real estate | 2021 |