| Meadowview (Borehamwood) Management Limited | Households | 1991 |
| Mears Group 2020 Ltd | Construction | 2025 |
| MED Mart Limited | Wholesale & retail | 2016 |
| Medburn Property Services Limited | Construction | 1999 |
| Medcare Health Solutions Limited | Health & social care | 2019 |
| Medequipment Ltd | Extraterritorial | 2015 |
| Medfoods International UK Ltd | Wholesale & retail | 2021 |
| Medi-Care Holdings Limited | Wholesale & retail | 2021 |
| Media Bounty Limited | Other services | 2008 |
| Media Button Ltd | Extraterritorial | 2020 |
| Media Digital Publishing Limited | Information & communication | 2011 |
| Media Monkeys Limited | Administrative & support | 2010 |
| Media Options Limited | Professional & scientific | 1982 |
| Media Woodwork Ltd | Information & communication | 2023 |
| Mediadvtech Ltd | Professional & scientific | 2016 |
| Medial Limited | Extraterritorial | 2016 |
| Medic Accountants (UK) LLP | | 2010 |
| Medic Accountants Limited | Professional & scientific | 2011 |
| Medic Finance Ltd | Financial services | 2018 |
| Medic GP Locum Limited | Professional & scientific | 2018 |
| Medic Locums Ltd | Other services | 2021 |
| Medic Payroll Limited | Professional & scientific | 2015 |
| Medic Umbrella Ltd | Professional & scientific | 2016 |
| Medical Professionals Consortium Ltd | Health & social care | 2015 |
| Medicx Healthcare Ltd | Health & social care | 2024 |
| Medinova PVT Limited | Health & social care | 2014 |
| Mediradar Ltd | Information & communication | 2020 |
| Mediterranean Growers Limited | Hospitality | 1982 |
| Medm Services Ltd | Health & social care | 2015 |
| Medrootz Limited | Professional & scientific | 2025 |
| Meds for Less Limited | Administrative & support | 2018 |
| Meer Group Ltd | Professional & scientific | 2019 |
| MEH Mutt Limited | Arts & recreation | 2026 |
| Melanie Clapton Education Services Ltd | Education | 2008 |
| Meldtek Ltd | Manufacturing | 2023 |
| Melek Property Ltd | Real estate | 2024 |
| Meltwind Advisory LLP | | 2014 |
| Melville Hotel Limited | Hospitality | 2001 |
| MEM ZIN Ltd | Hospitality | 2019 |
| Mema Development Ltd | Real estate | 2025 |
| Members Only Clothing Company Limited | Wholesale & retail | 1990 |
| Mena Electrical Ltd | Construction | 2011 |
| Merali Investments Ltd | Real estate | 2018 |
| Merali Medical Services Limited | Health & social care | 2010 |
| Meramir Ltd | Wholesale & retail | 2025 |
| Mercato London Ltd | Wholesale & retail | 2025 |
| Merebond Limited | Professional & scientific | 2024 |
| Merge Media Sport Ltd | Professional & scientific | 2026 |
| Meridian General Trading Ltd | Wholesale & retail | 2019 |
| Meridian Medical Products Ltd | Wholesale & retail | 2011 |
| Merko Builds Ltd | Construction | 2024 |
| Merlin & Associates Limited | Real estate | 2024 |
| Merrie Loot Care Homes (Uplands) Ltd | Health & social care | 2026 |
| Merrie Loot Holdings Ltd | Financial services | 2026 |
| Merrie Loot Property Ltd | Real estate | 2026 |
| Merrow Grange Management Limited | Real estate | 1987 |
| Mersey Building Solutions Ltd | Construction | 2021 |
| Merton Road Development Limited | Construction | 2013 |
| MES TM Ltd | Transport & logistics | 2021 |
| Meso ALS Limited | Financial services | 2016 |
| Meta Equity Holdings Limited | Financial services | 2023 |
| Metaenterprices Ltd | Wholesale & retail | 2006 |
| Metapb Limited | Wholesale & retail | 2024 |
| Metazn Limited | Wholesale & retail | 2021 |
| Metineja Ltd | Wholesale & retail | 2020 |
| Metline Properties Limited | Real estate | 2017 |
| Metox Ltd | Health & social care | 2012 |
| Metro Management Limited | Real estate | 1985 |
| Metropolis Pictures Ltd | Information & communication | 2019 |
| Metropolitan & District Securities Limited | Construction | 1992 |
| Metropolitan Chauffeurs Ltd | Transport & logistics | 2024 |
| Metropolitan London Private Chauffeurs Ltd | Transport & logistics | 2023 |
| Metropolitan Projects Ltd. | Construction | 2017 |
| Metrotyne Ltd | Information & communication | 2002 |
| Mevdia Limited | Professional & scientific | 2020 |
| Meyrick Productions Limited | Information & communication | 2016 |
| Mezmorize Limited | Real estate | 2012 |
| MFF Transport Limited | Transport & logistics | 2018 |
| MG Dental Services Limited | Health & social care | 2023 |
| MG Events Ltd | Administrative & support | 2015 |
| Mgeg Limited | Extraterritorial | 2021 |
| MGG Construction Ltd | Construction | 2018 |
| MGG Property Ltd | Real estate | 2024 |
| MGM Chauffeurs Limited | Transport & logistics | 2023 |
| MGV Capital Limited | Administrative & support | 2013 |
| MH Borehamwood Limited | Real estate | 2023 |
| MH Screening Limited | Construction | 2019 |
| MH Styles. Ltd Ltd | Transport & logistics | 2022 |
| Mh-Expreses Limited | Hospitality | 2024 |
| MHK Consultancy Limited | Professional & scientific | 2022 |
| Mi-Hope Mental Health Ltd | Health & social care | 2023 |
| Miah-Bibi Medicals Ltd | Health & social care | 2025 |
| Micael M Construction Ltd | Professional & scientific | 2023 |
| Michael K Howard (Milton Keynes) Limited | Professional & scientific | 2000 |
| Michael K Howard (Northampton) Limited | Professional & scientific | 1996 |
| Michael K Howard (Southern) Limited | Professional & scientific | 2001 |
| Michael K Howard (Thames Valley) Limited | Professional & scientific | 2001 |
| Michael Terry Ltd | Arts & recreation | 2019 |
| Michael Wigham Limited | Arts & recreation | 2006 |
| Micklev Ltd | Information & communication | 2015 |