| M.S.C.E. Ltd | Transport & logistics | 2014 |
| M2020 LLP | | 2020 |
| MA Business Solutions (Midlands) Limited | Information & communication | 2017 |
| MA Homes Group Limited | Real estate | 2021 |
| MA Platinum Property Maintenance Ltd | Construction | 2025 |
| Mabel Prime Ventures Ltd | Administrative & support | 2024 |
| Maciek Ltd | Transport & logistics | 2019 |
| Madz Valeting & Detailing Ltd | Administrative & support | 2021 |
| Maelor Foods Limited | Manufacturing | 2014 |
| Maelor Holdings Limited | Financial services | 2026 |
| Mahi Builders UK Ltd | Construction | 2025 |
| Mainh Logistics Ltd | Transport & logistics | 2025 |
| Majestic Transit Ltd | Transport & logistics | 2026 |
| Major Contractors Ltd | Construction | 2018 |
| Makh Consultancy Limited | Professional & scientific | 2026 |
| Mako Precision Engineering (Holdings) Limited | Financial services | 2005 |
| Mako Precision Engineering Limited | Manufacturing | 2007 |
| Maks Property Management Limited | Real estate | 2022 |
| Maks Services (UK) Limited | Transport & logistics | 2009 |
| Malisa Multy Concept Limited | Public administration | 2021 |
| Malthouse Homes Limited | Construction | 2006 |
| Mama Bros Ltd | Real estate | 2023 |
| Mamlakah Group Limited | Real estate | 2019 |
| Managed Precision Ltd | Professional & scientific | 2026 |
| Mandaleka Limited | Health & social care | 2025 |
| Manor Multi Academy Trust | Education | 2014 |
| Mantrac Ltd | Transport & logistics | 2025 |
| Maracas Investments Ltd | Professional & scientific | 2026 |
| Marble by Design Ltd | Manufacturing | 2024 |
| Marez Limited | Construction | 2014 |
| Mark Evans Haulage Ltd | Transport & logistics | 2024 |
| Marksman Ltd | Real estate | 2026 |
| MARTINTRANSPORT83 Ltd | Transport & logistics | 2022 |
| Mary Bond Court Management Company Limited | Households | 2022 |
| Maryoautomotive Ltd | Wholesale & retail | 2022 |
| Masala Events Limited | Hospitality | 2025 |
| Mashwest Ltd | Health & social care | 2012 |
| Master Housing Solutions Ltd | Real estate | 2024 |
| Master Maths Today Ltd | Education | 2026 |
| Material Ledger Ltd | Information & communication | 2026 |
| Matka Chai Ltd | Hospitality | 2020 |
| Matthew Bailey Limited | Construction | 2020 |
| Mavuso Engineering Limited | Manufacturing | 2018 |
| Mawanamotors Limited | Wholesale & retail | 2025 |
| Mawson Ltd | Wholesale & retail | 2026 |
| Mayfair Maintenance (Property Services) Ltd | Other services | 2015 |
| Mayisto Investments Limited | Construction | 2025 |
| May’S Hospitality and Care Ltd | Health & social care | 2023 |
| Mcauliffe Civil Engineering Limited | Water & waste | 1980 |
| Mcauliffe Demolition Limited | Water & waste | 2013 |
| Mcauliffe Group Ltd | Water & waste | 2008 |
| Mcauliffe Logistics Limited | Water & waste | 2014 |
| Mcenroe Midco 1 Limited | Financial services | 2021 |
| MCL Hinton Transport Limited | Transport & logistics | 2014 |
| Meadwood Developments Limited | Real estate | 1999 |
| Meat & VEG Centre Ltd | Wholesale & retail | 2017 |
| Meat Traders Ltd | Wholesale & retail | 2025 |
| Meatalicious Ltd | Wholesale & retail | 2026 |
| Mechatronics Ltd | Health & social care | 2023 |
| Medicine Box (Holborn) Ltd | Health & social care | 2022 |
| Medlink Staffing Solution Ltd | Administrative & support | 2025 |
| Meezan Limited | Wholesale & retail | 2023 |
| Mepran Properties Ltd | Real estate | 2023 |
| Merefield Group Limited | Construction | 2018 |
| Meritage Limited | Professional & scientific | 1987 |
| Merstone Ltd | Construction | 2025 |
| Meshach Properties Ltd | Real estate | 2024 |
| Metal & Waste Management Limited | Administrative & support | 2009 |
| Metal Spraying (UK) Ltd | Manufacturing | 1997 |
| Metno Limited | Health & social care | 2022 |
| MG UK Constructions Limited | Construction | 2019 |
| MH Hair and Cosmetics Ltd | Wholesale & retail | 2024 |
| Miagreenworld Ltd | Wholesale & retail | 2023 |
| Michael BB Limited | Transport & logistics | 2024 |
| Michtan Limited | Health & social care | 2018 |
| Mid-Counties Property Limited | Extraterritorial | 2016 |
| Midcon Group Ltd | Construction | 2018 |
| Middle MAN Export and Import. Ltd | Financial services | 2025 |
| Middleway Construction and Maintenance Ltd | Construction | 2025 |
| Midland Auto Repairs Limited | Wholesale & retail | 2014 |
| Midland Car Centre Ltd | Wholesale & retail | 2022 |
| Midland Fine Arts and Language Academy | Education | 2011 |
| Midland Formwork Limited | Construction | 2018 |
| Midland Sofa Ltd | Wholesale & retail | 2021 |
| Midland Tenancy Services Ltd | Administrative & support | 2024 |
| Midland Tyre Control Limited | Water & waste | 2002 |
| Midland Water Systems Ltd | Professional & scientific | 2003 |
| Midlands for Reform UK Ltd. | Other services | 2025 |
| Midlands Highway Logistics Ltd | Transport & logistics | 2016 |
| Midlands Quantity Surveying & Estimating Ltd | Professional & scientific | 2022 |
| Midlands Street & Ground Works Ltd | Water & waste | 2021 |
| Midlands Tech Ltd | Manufacturing | 2020 |
| Midlothian Dog Grooming Ltd | Agriculture & fishing | 2023 |
| Miles Relocation Services Ltd | Transport & logistics | 2024 |
| Militar Construction Limited | Construction | 2021 |
| Mill Vintage Ltd | Wholesale & retail | 2026 |
| Millard Group Holdings Ltd | Construction | 2018 |
| Millenium Tyres Ltd | Wholesale & retail | 2026 |
| Mills Ductwork Systems Ltd | Manufacturing | 2021 |
| Millwells Developments Ltd | Real estate | 2025 |