| Manorwood Building Ltd | Construction | 2025 |
| Manorwood Building Services Limited | Other services | 2019 |
| Mans Wholesale Limited | Wholesale & retail | 2023 |
| Mansion House (Edgbaston) Management Ltd | Households | 2016 |
| Mansold 7 Limited | Wholesale & retail | 2020 |
| Mantra Training Ltd | Education | 2016 |
| Manu Swamy Solution Ltd | Information & communication | 2016 |
| Maple Contracts Ltd | Manufacturing | 2022 |
| Maple Leaf Counselling Limited | Education | 2025 |
| Maple Tree Partners LLP | | 2019 |
| Maplewood Ltd | Construction | 2021 |
| MAR 50 Limited | Construction | 2013 |
| MAR Land Reclamation Limited | Water & waste | 1999 |
| Marbal Properties Limited | Administrative & support | 1989 |
| Marble Life Limited | Administrative & support | 2010 |
| Marca Strategy Ltd | Administrative & support | 2025 |
| March Property Co Limited | Real estate | 2016 |
| Marcus Roofing (Midlands) Ltd | Administrative & support | 2023 |
| Marflo Investments Limited | Administrative & support | 2024 |
| Marford Road (Wheathampstead) Limited | Real estate | 2026 |
| Marginos Ltd | Professional & scientific | 2017 |
| Marianne Consulting Limited | Health & social care | 2016 |
| Marigom Ltd | Real estate | 2018 |
| Marilyns Nightclub Limited | Hospitality | 2015 |
| Marina Rose Hair Design Limited | Other services | 2018 |
| Marine Parts Direct LLP | | 2018 |
| Mario XH Ltd | Wholesale & retail | 2020 |
| Mariposa Plus Limited | Wholesale & retail | 2020 |
| Mariyam Homes Ltd | Real estate | 2025 |
| Marjoy Ltd | Administrative & support | 2022 |
| Mark a Mcdowell Ltd | Transport & logistics | 2023 |
| Mark Anthony Mcdowell Limited | Extraterritorial | 2025 |
| Mark Benton Limited | Information & communication | 2007 |
| Mark Grigg Executive Recruitment Limited | Administrative & support | 2019 |
| Mark Kane Fire Door Audit Ltd | Public administration | 2025 |
| Mark Love Site Services Ltd | Construction | 2021 |
| Mark Stevens Lift Services Limited | Construction | 2004 |
| Mark Wilkes Anaesthetic Company Limited | Health & social care | 2012 |
| Marketplates Limited | Wholesale & retail | 2025 |
| Marlex Property Limited | Real estate | 2026 |
| Marley Entertainment Ltd | Arts & recreation | 2020 |
| Marlin Group Holdings Limited | Financial services | 2025 |
| Marlodge (Monnow) Limited | Real estate | 1957 |
| Marlow Road (Henley on Thames) Limited | Construction | 2023 |
| Marmalade Cashmere Limited | Wholesale & retail | 2009 |
| Marmion House Hotel Limited | Hospitality | 2026 |
| Marque Associates Limited | Administrative & support | 2015 |
| Marrinan Newco Ltd | Professional & scientific | 2024 |
| Mars 4 Homes Ltd | Real estate | 2025 |
| Mars Infotech Ltd | Information & communication | 2024 |
| Marsden Capital Limited | Construction | 2022 |
| Marsden Kiwi Homes Limited | Construction | 2025 |
| Marsh Building and Electrical Limited | Construction | 2011 |
| Marsh House Limited | Professional & scientific | 1982 |
| Marsh JAW and GAP Limited | Administrative & support | 2014 |
| Marshall Management Services Ltd | Administrative & support | 2007 |
| Marshall Murray Consulting Limited | Construction | 2020 |
| Marshalls (Plumbing and Building Development ) Limited | Construction | 1999 |
| Marshfield Limited | Construction | 2017 |
| Marshvale Ltd | Real estate | 2021 |
| Marsin Bakers Ltd. | Manufacturing | 2018 |
| Marss Properties Limited | Real estate | 2021 |
| Marston Gate Management Company Limited | Real estate | 1999 |
| Marthaola Limited | Health & social care | 2023 |
| Martin Archer Electrical Limited | Extraterritorial | 2013 |
| Martin Bruce Homes Limited | Construction | 2017 |
| Martin Carter Associates Limited | Professional & scientific | 2014 |
| Martin Hall Expert Services Ltd | Professional & scientific | 2025 |
| Martin Morgan Builders Limited | Construction | 2015 |
| Martini Vehicle Recovery Limited | Wholesale & retail | 2003 |
| Martinkova Management Consulting Limited | Professional & scientific | 2022 |
| Martinvale Developments Limited | Real estate | 1967 |
| Martyn Wilkins LLP | | 2003 |
| Marvelift Limited | Other services | 2019 |
| Marwaha and Daughters Housing Ltd | Real estate | 2021 |
| Mary ANN Group Limited | Financial services | 2025 |
| Mary ANN Properties Limited | Construction | 1985 |
| MAS Wholesale Limited | Wholesale & retail | 2013 |
| Masa Solutions Ltd | Information & communication | 2018 |
| Masala Art Restaurants Limited | Hospitality | 2001 |
| Maseere Limited | Wholesale & retail | 2022 |
| Masi UK Finance Limited | Professional & scientific | 2026 |
| Masiah Welfare Trust C.I.C. | Health & social care | 2020 |
| Masion Group Limited | Wholesale & retail | 2026 |
| Masion Motor Sales Limited | Wholesale & retail | 2026 |
| Mason Auto Parts Limited | Wholesale & retail | 2018 |
| Mason Construction (West Midlands) Limited | Construction | 2017 |
| Mason Yardley Trust | Other services | 2018 |
| Masonic Hall Ltd | Real estate | 2022 |
| Massage Chair Distributors Limited | Wholesale & retail | 2003 |
| Masson Beckett Limited | Administrative & support | 2023 |
| Mast Services Ltd | Information & communication | 2009 |
| Master Rights of Dixy Chicken Midlands Ltd | Professional & scientific | 2019 |
| Masterglaze Limited | Extraterritorial | 2000 |
| Masterjoint Limited | Extraterritorial | 2011 |
| Masterplan Group Holdings Ltd | Financial services | 2025 |
| Mastertrace Ltd | Information & communication | 2016 |
| Masummer Properties Limited | Real estate | 2019 |
| MAT Armstrong Holdings Ltd | Financial services | 2025 |
| MAT Armstrong Ltd | Wholesale & retail | 2020 |