| M P Crowe & SON Limited | Manufacturing | 2011 |
| M Rafiq Properties Limited | Real estate | 2025 |
| M S Chilled Foods Group Ltd | Hospitality | 2020 |
| M S H Motors Ltd | Wholesale & retail | 2018 |
| M T Skips Limited | Administrative & support | 2017 |
| M W Sarkar Ltd | Arts & recreation | 2024 |
| M W Taylor Ltd | Construction | 2022 |
| M Wilkes Demolition & Site Services Limited | Construction | 2017 |
| M&D UGO Limited | Health & social care | 2023 |
| M&G Builders Limited | Information & communication | 2025 |
| M&K Contracting Services Ltd | Extraterritorial | 2021 |
| M&L Peters Plumbing & Heating Services Ltd | Construction | 2008 |
| M&S Holdings and Investments Ltd | Financial services | 2024 |
| M&S Properties Midlands Ltd | Real estate | 2024 |
| M&S Windows and Property Services Ltd | Construction | 2018 |
| M'Poun NDE UK Association | Other services | 2021 |
| M-Five International Limited | Financial services | 2024 |
| M. Webb Landscaping Limited | Administrative & support | 2026 |
| M.A. Plastering Ltd | Construction | 2016 |
| M.A.P. Holistic Ltd | Health & social care | 2015 |
| M.D Car Transport Limited | Wholesale & retail | 2025 |
| M.E.Racing Ltd | Wholesale & retail | 2024 |
| M.G. Welding Plant Limited | Wholesale & retail | 1987 |
| M.H Star Builders Limited | Construction | 2025 |
| M.S.T.A Properties Limited | Construction | 2022 |
| M.W. Transport Limited | Transport & logistics | 2004 |
| M.W.Trade Cars Ltd | Wholesale & retail | 2020 |
| M2A Accountancy Limited | Professional & scientific | 2013 |
| M3 Education UK Ltd | Education | 2025 |
| M6 Group Limited | Real estate | 2002 |
| M6 Properties Limited | Real estate | 2002 |
| M6 Securities Limited | Financial services | 2002 |
| MA Heating and Plumbing Services Limited | Construction | 2015 |
| Maan News Limited | Wholesale & retail | 2003 |
| Maava Ltd | Wholesale & retail | 2026 |
| Mabel Property Ventures Ltd | Real estate | 2025 |
| Mabid Beauty Lounge Limited | Other services | 2026 |
| MAC Nicklin Transport Ltd | Transport & logistics | 2025 |
| MAC Prime Ltd | Wholesale & retail | 2025 |
| Macprop Developments Limited | Construction | 2017 |
| Macram Construction Ltd | Administrative & support | 2020 |
| Macram Ltd | Administrative & support | 2019 |
| Macrowest Ltd | Transport & logistics | 2023 |
| Madebybeing Limited | Professional & scientific | 2012 |
| Madeley Computer Systems Limited | Information & communication | 1985 |
| Madi 2020 Ltd | Real estate | 2023 |
| Madison Logistics (WM) Limited | Transport & logistics | 2025 |
| Madison Technology Limited | Information & communication | 2004 |
| Madni Mega Mart Ltd | Wholesale & retail | 2026 |
| MAG Architecture Limited | Professional & scientific | 2012 |
| MAG Cars Ltd | Wholesale & retail | 2016 |
| MAG Optica Ltd | Wholesale & retail | 2020 |
| Magda's Cleaning Ltd | Administrative & support | 2025 |
| Magic Touch Network CIC | Education | 2021 |
| Magical Barbers Ltd | Other services | 2025 |
| Magna College Ltd | Education | 2024 |
| Magnafleck Ltd | Wholesale & retail | 2018 |
| Magnarent Limited | Real estate | 1987 |
| MAID4U Cleaning Services Ltd | Administrative & support | 2025 |
| Mailbox Estates Limited | Real estate | 2018 |
| Mainline Electronics Property Limited | Real estate | 1995 |
| Mainn Transport Ltd | Transport & logistics | 2025 |
| Majala Limited | Real estate | 2018 |
| Majestic Kebabs Limited | Hospitality | 2026 |
| Make Living Easy Limited | Wholesale & retail | 2017 |
| Maks Healthcare Services Ltd | Extraterritorial | 2013 |
| Male Room (Barbers) Limited | Other services | 2011 |
| Mallard Industrial Limited | Water & waste | 2016 |
| Mallett Jones Limited | Professional & scientific | 2009 |
| Mallin Lift Services Ltd | Manufacturing | 2025 |
| Malson Homes Limited | Real estate | 2017 |
| Malvern Garden Rooms Ltd | Construction | 2018 |
| Management Midlands Ltd | Arts & recreation | 2025 |
| Management Services West Midlands Ltd | Arts & recreation | 2021 |
| Manchester Pain Reports Limited | Professional & scientific | 2019 |
| Maneque Ltd | Health & social care | 2025 |
| Manex Accountants Limited | Professional & scientific | 2001 |
| Mani Bell Ltd | Wholesale & retail | 2026 |
| Manicares Limited | Administrative & support | 2019 |
| Manny B Media Ltd | Information & communication | 2025 |
| Manny.B Locum Ltd | Health & social care | 2023 |
| Manor Gardens (Hackmans Gate) Management Company Limited | Households | 2019 |
| Manor House Design & Build Limited | Construction | 2014 |
| Mantech Holdings Limited | Financial services | 2018 |
| Maple Tool Hire Limited | Wholesale & retail | 1993 |
| Maple Workwear Limited | Wholesale & retail | 2011 |
| Maplefine Limited | Transport & logistics | 1974 |
| MAQ Trading Limited | Wholesale & retail | 2016 |
| Marabek Services Limited | Real estate | 2024 |
| Marbara Estates Limited | Real estate | 2004 |
| Marble Court (Lichfield) Management Company Limited | Households | 2007 |
| Marcegaglia (UK) Limited | Manufacturing | 1992 |
| Marek Aleksandrowicz Limited | Health & social care | 2013 |
| Marflow Holdings Limited | Professional & scientific | 2006 |
| Marian House Care Home Limited | Administrative & support | 2016 |
| Marigold Care Services Ltd | Administrative & support | 2020 |
| Marius Super Market Limited | Wholesale & retail | 2023 |
| Mark Anthony Robinson Ltd | Wholesale & retail | 2025 |
| Mark Breakwell Limited | Construction | 2008 |
| Mark Butler Limited | Arts & recreation | 2008 |