| Maverick Customwear Limited | Wholesale & retail | 2012 |
| MAX Curry Ltd | Hospitality | 2024 |
| Maxam UK Limited | Manufacturing | 2005 |
| Maxco Drilling Services Ltd | Manufacturing | 2024 |
| Maxco Engineering Limited | Manufacturing | 2009 |
| Maxcool Air Conditioning Services Ltd | Construction | 2017 |
| Maximal Investments Limited | Real estate | 2022 |
| Maximindme Ltd | Information & communication | 2019 |
| Maxpham Property Investments Ltd | Real estate | 2026 |
| Maxwell Richards Limited | Wholesale & retail | 2015 |
| Maxwells Demon Limited | Information & communication | 2013 |
| MAY Leigh Limited | Arts & recreation | 2023 |
| MAY2CARE Ltd | Health & social care | 2025 |
| Mayday Marine Limited | Professional & scientific | 2002 |
| Mayfair Strategic Partners Ltd | Financial services | 2020 |
| Mayfield View Management Company Limited | Real estate | 2007 |
| Mayfly Project Management Limited | Construction | 2024 |
| Mayhao Limited | Wholesale & retail | 2010 |
| Maynews Limited | Wholesale & retail | 1984 |
| Mazk Healthcare Limited | Wholesale & retail | 2026 |
| MB Builders & Joinery Limited | Construction | 2008 |
| MB Mortgages Limited | Financial services | 2016 |
| MB17 Properties Ltd | Real estate | 2025 |
| MBA Ecom Ltd | Wholesale & retail | 2026 |
| MBF Electrical Limited | Construction | 2014 |
| MBH Nursing Services Limited | Health & social care | 2021 |
| MBS Trading Limited | Transport & logistics | 2019 |
| MC Timber Products Ltd | Manufacturing | 2015 |
| MCD Automotive's Ltd | Wholesale & retail | 2024 |
| Mcdonald 2004 Limited | Professional & scientific | 2004 |
| Mcdonald Associates Limited | Financial services | 1996 |
| Mcdonald Sipp Trustees Limited | Administrative & support | 2021 |
| Mcdonald Ssas Trustees Limited | Administrative & support | 2021 |
| Mcdonald Trustees Limited | Administrative & support | 2000 |
| Mcdoodles Ltd | Hospitality | 2024 |
| Mcgirrs Window Cleaning Limited | Administrative & support | 2025 |
| MCI & Transport Ltd | Wholesale & retail | 2022 |
| MCI International Limited | Information & communication | 2002 |
| MCJ Financial Ltd | Professional & scientific | 2025 |
| Mckeown & Scullin Solutions Ltd | Information & communication | 2024 |
| Mclaren Fire & Security Services Ltd | Construction | 2026 |
| Mclellan and Sons Commercial Vehicle Painting Ltd | Wholesale & retail | 2012 |
| MCM Consultancy Limited | Professional & scientific | 2019 |
| MCP Carpets Limited | Construction | 2007 |
| MCR Service & Repairs Ltd | Manufacturing | 2023 |
| Mcrb Property Limited | Real estate | 2013 |
| MCS Accounting Ltd | Professional & scientific | 2023 |
| Mcsm Limited | Health & social care | 2023 |
| MD Clinic UK Ltd | Health & social care | 2022 |
| MD Fire Compliance Ltd | Public administration | 2022 |
| MD GAS Services (Midlands) Ltd | Construction | 2019 |
| MD Hair Chesterfield Ltd | Other services | 2021 |
| Mdbas CF Limited | Professional & scientific | 2023 |
| Mdel Fleet Management Limited | Wholesale & retail | 2019 |
| MDG Health & Safety Training Solutions Ltd | Education | 2016 |
| MDP Developments Limited | Construction | 2021 |
| MDS Technical Services Ltd | Wholesale & retail | 2022 |
| MDW Services Chesterfield Limited | Construction | 2011 |
| ME Vineyard Works Limited | Agriculture & fishing | 2021 |
| Meadow Grange Residential Home Limited | Health & social care | 2002 |
| Meadowland Holdings Limited | Financial services | 2020 |
| Meale and Meale Limited | Extraterritorial | 2013 |
| Mechanical Electrical & Control Services Limited | Construction | 2013 |
| Mechanicus Engineering Ltd | Professional & scientific | 2025 |
| Mechdev Ltd | Manufacturing | 2023 |
| MEDIC88 Ltd | Health & social care | 2023 |
| Mediguard Limited | Information & communication | 2022 |
| Mediterranean Exotic Interiors Limited | Wholesale & retail | 2007 |
| Medway Closures Limited | Manufacturing | 1996 |
| Medway Packaging Systems Limited | Administrative & support | 2000 |
| Meersbrook Electrical Limited | Construction | 2008 |
| Megmeister Limited | Manufacturing | 2014 |
| Mel-Dan Engineering Limited | Professional & scientific | 2004 |
| Melanie Shaw Financial Wellbeing Ltd | Professional & scientific | 2026 |
| Melfort Construction Holdings Limited | Construction | 2020 |
| Melfort Construction Services Limited | Construction | 1997 |
| Melfort Joinery Services Limited | Construction | 2023 |
| Melfort Properties Limited | Real estate | 2021 |
| Melfort Site Services Limited | Administrative & support | 2021 |
| Mellow Relief Ltd | Real estate | 2023 |
| Melvify Ltd | Administrative & support | 2023 |
| Melwood Projects Limited | Construction | 2010 |
| Memo Management Limited | Professional & scientific | 2023 |
| Memory Recall 3 Limited | Real estate | 2007 |
| Memory Recall 4 Limited | Real estate | 2007 |
| Memory Recall Limited | Real estate | 2003 |
| Memphco Limited | Financial services | 2021 |
| Men's Conscious Collective CIC | Health & social care | 2025 |
| Mensayhub Ltd | Wholesale & retail | 2024 |
| Mentor F.L.T. Training Limited | Administrative & support | 2001 |
| Merak Heating Limited | Construction | 2026 |
| Merce Engineering Ltd. | Manufacturing | 2011 |
| Mercia Housing Ltd | Real estate | 2026 |
| Mercian Accounting Ltd | Professional & scientific | 2022 |
| Mercian Group Ltd | Financial services | 2023 |
| Mercian Property Holdings Ltd | Real estate | 2023 |
| Mercy Services Limited | Wholesale & retail | 2004 |
| Meredith Sales & Hire Ltd | Administrative & support | 2026 |
| Meridian ENG Services (UK) Limited | Other services | 2005 |
| Meridian Seahorse Ltd | Hospitality | 2009 |