| M Cosgrove Civils Limited | Construction | 2016 |
| M D Connections Limited | Extraterritorial | 1999 |
| M D Murray Ltd | Health & social care | 2015 |
| M Firkins Ltd | Transport & logistics | 2018 |
| M G O Consultancy Ltd | Professional & scientific | 2024 |
| M Griffin Electrical Services Ltd | Construction | 2010 |
| M H ALI Ltd | Real estate | 2025 |
| M H Heating Solutions Ltd | Construction | 2021 |
| M I Business Services Limited | Information & communication | 2008 |
| M J Boyce Limited | Construction | 2008 |
| M J Boyce Surfacing Limited | Construction | 2015 |
| M J Coles Construction Services Limited | Construction | 2016 |
| M J Coles Holding Limited | Financial services | 2022 |
| M J Coles Properties Limited | Real estate | 2022 |
| M J D Brickwork Limited | Construction | 2011 |
| M J Halton Electrical Services Limited | Construction | 2006 |
| M J Halton Group Facility Services Ltd | Administrative & support | 2024 |
| M J Solar Limited | Construction | 2022 |
| M Jenkins Construction Ltd | Construction | 2011 |
| M K Specialist Cars Ltd | Wholesale & retail | 2016 |
| M Kenny (Decorators) Limited | Construction | 1990 |
| M L Construction Limited | Construction | 2015 |
| M Lindsay Properties Limited | Real estate | 2020 |
| M MIR Limited | Health & social care | 2007 |
| M Naqqash Ltd | Administrative & support | 2026 |
| M Newton Painting Ltd | Construction | 2023 |
| M P K Controls Holdings Limited | Financial services | 2025 |
| M P K Controls Ltd. | Manufacturing | 1988 |
| M P Lewis Estates Ltd. | Real estate | 2015 |
| M P Lewis Holdings Ltd | Real estate | 2015 |
| M POP Dental Laboratory Ltd | Health & social care | 2021 |
| M Power & Sons Limited | Manufacturing | 2016 |
| M Rent Limited | Real estate | 2024 |
| M Richards Carpentry Ltd | Construction | 2020 |
| M Ruby Limited | Real estate | 2022 |
| M S Property Developers Ltd | Construction | 2008 |
| M Saidler Limited | Information & communication | 2011 |
| M Stone Construction Ltd | Construction | 2017 |
| M Truslove Tree Surgery Ltd | Administrative & support | 2024 |
| M Watts Roofing Ltd | Construction | 2019 |
| M&A Solutions Limited | Real estate | 2024 |
| M&B Ginger Blue Ltd | Hospitality | 2026 |
| M&B Quickbloom Bazar Ltd | Wholesale & retail | 2023 |
| M&D Doody Transport Limited | Transport & logistics | 2014 |
| M&D Engineering Limited | Professional & scientific | 2025 |
| M&E Coffees Ltd | Hospitality | 2022 |
| M&Jb Property Ltd | Real estate | 2020 |
| M&L Designer Ltd | Manufacturing | 2019 |
| M&M Family 10 Ltd | Wholesale & retail | 2025 |
| M&M Family 11 Ltd | Wholesale & retail | 2025 |
| M&M Family 12 Ltd | Wholesale & retail | 2026 |
| M&M Family Two Ltd | Wholesale & retail | 2016 |
| M&M Maintenance Services Ltd | Administrative & support | 2018 |
| M&Mocktails Ltd | Hospitality | 2025 |
| M&R Homewares Limited | Wholesale & retail | 2021 |
| M&T Properties Solihull Ltd | Real estate | 2019 |
| M-Tac Building Services Ltd | Construction | 2026 |
| M-Tec Building Property Management Limited | Households | 2006 |
| M. & R. Kirkham & Sons Limited | Agriculture & fishing | 1979 |
| M. J. Smallwood Construction Ltd | Construction | 2017 |
| M. Mcintyre & Sons Ltd | Construction | 2022 |
| M. Smallwood Building Services Ltd | Construction | 2017 |
| M. T. James Limited | Administrative & support | 2012 |
| M.A.D.Tech.Solutions. Ltd | Other services | 2018 |
| M.A.R. Steriliser Services Limited | Administrative & support | 2001 |
| M.B. & N Credit Services (Holdings) Limited | Administrative & support | 2000 |
| M.G.A. Consultants Limited | Real estate | 1994 |
| M.G.M. Roofing & Cladding Ltd | Construction | 2001 |
| M.I.B. Speciality Sales Limited | Administrative & support | 2020 |
| M.J.K. Design Limited | Professional & scientific | 1989 |
| M.R.S Autos Mobile Mechanic Ltd | Wholesale & retail | 2025 |
| M.S.L. Play Inspections Limited | Professional & scientific | 2018 |
| M.V. Kelly Limited | Construction | 1995 |
| M2MEX Ltd | Professional & scientific | 2024 |
| M3 Restaurants Ltd | Hospitality | 2024 |
| M3B Ltd | Real estate | 2019 |
| M3FORYOU Ltd | Wholesale & retail | 2024 |
| M3K Properties Ltd | Real estate | 2018 |
| M7 Holdings Limited | Wholesale & retail | 2025 |
| M9 Events Ltd | Arts & recreation | 2021 |
| MA & SA Properties Limited | Real estate | 2024 |
| MA Barbering Ltd | Other services | 2022 |
| MA Merchandise Ltd | Wholesale & retail | 2022 |
| MAA Foods UK Limited | Manufacturing | 2020 |
| Maanek and Preet Property Ltd | Real estate | 2018 |
| MAB Commerce Ltd | Households | 2025 |
| MAC Contracts Limited | Construction | 2014 |
| MAC Express Transport Limited | Transport & logistics | 2020 |
| MAC MEC Fabrications Limited | Professional & scientific | 2024 |
| MAC Medical Services Ltd | Health & social care | 2016 |
| Macaw Limited | Professional & scientific | 2002 |
| Macaw Security Solutions Limited | Administrative & support | 2018 |
| MACHINE4U Ltd | Wholesale & retail | 2016 |
| Machomindz Limited | Other services | 2025 |
| Mack 5855 (2016) Limited | Administrative & support | 2023 |
| Mackenzie's Holdings Limited | Financial services | 2022 |
| Mackenzie's Ltd | Construction | 2021 |
| Maclay Flooring Ltd | Real estate | 2026 |
| Maclean Legal LLP | | 2019 |
| MAD Hatter's Tea Party Children's Charity Limited | Other services | 2009 |