| MBL Ventures Ltd | Financial services | 2024 |
| Mbmfm Ltd | Professional & scientific | 2020 |
| MBS Fashion Limited | Wholesale & retail | 2023 |
| Mbulzi Consulting Ltd | Information & communication | 2022 |
| MC Black Arrow Ltd | Transport & logistics | 2017 |
| Mcaris CAD Ltd | Professional & scientific | 2026 |
| Mcarthur Roofing Services Ltd | Construction | 2025 |
| Mccabe Travel Limited | Administrative & support | 1987 |
| MCD Office Supplies Ltd | Wholesale & retail | 2004 |
| Mcfadden Property Maintenance Ltd | Administrative & support | 2015 |
| MCG Business Solutions Limited | Professional & scientific | 2015 |
| Mcintosh Health Partners Ltd | Professional & scientific | 2016 |
| Mckenna Creative Ltd | Arts & recreation | 2021 |
| Mckillop Engineering Limited | Manufacturing | 2002 |
| MCS Plastering Ltd | Construction | 2024 |
| MD Cogent Ltd. | Professional & scientific | 2012 |
| MD Construction Engineering Ltd | Extraterritorial | 2014 |
| MD Innovate Construction Ltd | Construction | 2024 |
| MD Residential Limited | Real estate | 2012 |
| Mdgsheq Limited | Professional & scientific | 2019 |
| MDJ Mortgages Ltd | Financial services | 2020 |
| MDJ Properties Limited | Construction | 2016 |
| MDL Subscriptions Limited | Extraterritorial | 1979 |
| MDL Wood Limited | Real estate | 2022 |
| MDN Fusion Limited | Professional & scientific | 2003 |
| MDR Heating and Plumbing Ltd | Construction | 2020 |
| Mdsn Limited | Professional & scientific | 2014 |
| Meadowrose Scientific Limited | Manufacturing | 1994 |
| Meaningful Travel Limited | Financial services | 2020 |
| Mechenet Ltd | Information & communication | 2019 |
| Medcold Limited | Manufacturing | 2016 |
| Medcraft Holdings Limited | Financial services | 2013 |
| Medena Communications Limited | Professional & scientific | 2000 |
| Medi-Cart International Limited | Professional & scientific | 1997 |
| Media Distribution Services Ltd | Professional & scientific | 2011 |
| Medic Aesthetics Limited | Health & social care | 2025 |
| Medic Datasystems Limited | | 1985 |
| Medical Innovations Group Holdings Limited | Financial services | 2007 |
| Medical Innovations Group Ltd | Financial services | 2003 |
| Medicess Limited | Health & social care | 2004 |
| Medisafe Holdings Ltd | Financial services | 2016 |
| Medisafe UK Limited | Manufacturing | 1990 |
| Medius Technology Limited | Information & communication | 2012 |
| Medops Solutions Ltd | Professional & scientific | 2023 |
| Meehan Productions Ltd | Information & communication | 2006 |
| Meldiz Ltd | Hospitality | 2022 |
| Melissa Horn Consulting Ltd | Administrative & support | 2021 |
| Mellowes Ltd | Real estate | 2023 |
| Memo Events Ltd | Administrative & support | 2013 |
| Mental Health Awareness Club UK Ltd | Wholesale & retail | 2023 |
| Meravis Estates Limited | Real estate | 2026 |
| Mercedez Select Ltd | Wholesale & retail | 2026 |
| Mercona (G.B.) Limited | Manufacturing | 1993 |
| Mercury Driving School Ltd | Education | 2022 |
| Mercy Care Services Ltd | Administrative & support | 2019 |
| Mercy Home Care Services Ltd | Health & social care | 2018 |
| Meridian Controls Limited | Professional & scientific | 1998 |
| Messner Development Limited | Other services | 2016 |
| Meta Electrical Services Limited | Construction | 2025 |
| Methaya Limited | Other services | 2013 |
| Metricise Ltd | Real estate | 2024 |
| Metro Recovery Ltd | Transport & logistics | 2026 |
| Metropolis Data Ltd | Information & communication | 2024 |
| Mettagarden Ltd. | Administrative & support | 2018 |
| Meyer Sutherland Properties Ltd | Real estate | 2024 |
| Meyer-Wulff Consultancy Ltd | Professional & scientific | 2022 |
| Meyn Poultry Equipment Limited | Wholesale & retail | 1973 |
| MF Associates Limited | Administrative & support | 2012 |
| MFA Holdings Limited | Financial services | 2015 |
| MGK Property Services Ltd | Real estate | 2024 |
| MH Autos (Basingstoke) Limited | Wholesale & retail | 2009 |
| MH Custom Electrical Ltd | Construction | 2025 |
| Mhcw Ltd | Wholesale & retail | 2023 |
| MHE Finance Limited | Financial services | 2011 |
| MHR Carpentry and Joinery Ltd | Manufacturing | 2024 |
| MI Decorators Ltd | Construction | 2013 |
| Mice Connect Group Limited | Information & communication | 2025 |
| Michael Dickson Associates Limited | Information & communication | 2025 |
| Michael O'Dwyer Consultancy Ltd | Professional & scientific | 2012 |
| Michael Treatments Limited | Health & social care | 2026 |
| Mici One Ltd | Transport & logistics | 2025 |
| Mick Gooding & Co Ltd | Real estate | 2020 |
| Micore Ltd | Manufacturing | 2026 |
| Middle East Trading Establishment Limited | Wholesale & retail | 2021 |
| Middle Recruitment Limited | Administrative & support | 2023 |
| Middlesex Aerospace Limited | Manufacturing | 2016 |
| Middlesex Automation Limited | Professional & scientific | 1964 |
| Middlesex Group Limited | Manufacturing | 1962 |
| Middlesex Machine Tool (Sales) Limited | Professional & scientific | 1954 |
| Middlesex Tool Gauge Co.Limited | Professional & scientific | 1956 |
| Midland Phone Services Ltd | Professional & scientific | 2013 |
| Midland Phones Limited | Professional & scientific | 2003 |
| Miformat Ltd | Construction | 2009 |
| Mike Brown Services Limited | Extraterritorial | 2008 |
| Mikes Garden Services Ltd | Administrative & support | 2011 |
| Mikul Ltd | Transport & logistics | 2014 |
| Milad Shadrooh Limited | Health & social care | 2016 |
| Mildmay Bloodstock Limited | Agriculture & fishing | 2003 |
| Milexia UK Ltd. | Information & communication | 1990 |
| Mill Wheel Cottages Limited | Real estate | 2022 |