| Medusa Stucco Limited | Construction | 2020 |
| Medusa Surveillance and Close Protection Ltd | Administrative & support | 2024 |
| Medworldapp Ltd | Information & communication | 2025 |
| Medyago Digital Ltd | Wholesale & retail | 2026 |
| Meempire Ltd | Wholesale & retail | 2025 |
| Meerbay Ltd | Wholesale & retail | 2025 |
| Meface Ltd | Manufacturing | 2008 |
| Mega Consulting Ltd | Information & communication | 2026 |
| Mega Mile Ltd | Transport & logistics | 2021 |
| Mehra & Associates Limited | Health & social care | 2017 |
| Meihao Studio Ltd | Information & communication | 2025 |
| Mekhana Ltd | Wholesale & retail | 2026 |
| Meksi Ltd | Wholesale & retail | 2024 |
| Melanie Cormack-Hicks Fine Artist Ltd | Wholesale & retail | 2021 |
| Melanie Pilmer Limited | Other services | 2026 |
| Melanobd Ltd | Wholesale & retail | 2024 |
| Melber Ltd | Professional & scientific | 2019 |
| Melia Developments Ltd | Real estate | 2021 |
| Meliora Care Limited | Real estate | 2024 |
| Melle Ltd | Wholesale & retail | 2024 |
| Melling Web Studios Ltd | Information & communication | 2025 |
| Mellis Design Limited | Professional & scientific | 2018 |
| Mellowmill Ltd | Information & communication | 2026 |
| Melodies Care Ltd | Health & social care | 2022 |
| Melona Medical Staffing Ltd | Administrative & support | 2026 |
| Melona Recruitment Group Ltd | Administrative & support | 2025 |
| Melos Group Limited | Information & communication | 2020 |
| Membrane Labs LLP | | 2014 |
| Memfis Limited | Administrative & support | 2023 |
| Memnice Limited | Professional & scientific | 2017 |
| Memoirist Ltd | Extraterritorial | 2024 |
| Memorial Stair Climb CIC | Public administration | 2026 |
| Memory Card Ltd | Manufacturing | 2024 |
| Memory Holmes Ltd | Wholesale & retail | 2023 |
| MEN Achieve Through Empowerment (Mate) CIC | Health & social care | 2024 |
| Mendara Ltd | Information & communication | 2026 |
| Menna Homes Ltd | Real estate | 2025 |
| Mental Development UK Ltd | Transport & logistics | 2016 |
| Mental Jewels Ltd | Manufacturing | 2026 |
| Mentivara Tech Ltd | Information & communication | 2026 |
| Mentora Money Ltd | Education | 2023 |
| Meow Plaza Ltd | Wholesale & retail | 2024 |
| Mercato Trading Ltd | Wholesale & retail | 2026 |
| Merchant Global Limited | Wholesale & retail | 2020 |
| Merchant House Properties Limited | Real estate | 2016 |
| Merchants Place (Bury ST Edmunds) Management Company Limited | Households | 2012 |
| Mercurial Engineering Consulting Ltd | Professional & scientific | 2026 |
| Mercuriel Ltd | Professional & scientific | 2025 |
| Mercury Products Ltd | Wholesale & retail | 2015 |
| Meriad Property Investments Ltd | Real estate | 2025 |
| Meridara Ltd | Information & communication | 2026 |
| Meridian Forge Group Ltd | Construction | 2026 |
| Meridian Resources Group Co Limited | Mining & quarrying | 2023 |
| Meridian Resources UK Limited | Administrative & support | 2022 |
| Meriscorp UK Limited | Real estate | 2025 |
| Meritor Design & Development Limited | Information & communication | 2014 |
| Merlin East Anglia Limited | Construction | 2016 |
| Merlin Services Wiltshire Ltd | Administrative & support | 2008 |
| Mermaid Close Management Company Limited | Households | 1988 |
| Merry & Co Limited | Professional & scientific | 2000 |
| Merry Accountancy Services Limited | Professional & scientific | 2000 |
| Merryn AI Ltd | Information & communication | 2026 |
| Merryprop Limited | Real estate | 2016 |
| Merseyshine Ltd | Administrative & support | 2026 |
| Mertonford Property Group Limited | Hospitality | 2026 |
| Merú London Ltd | Manufacturing | 2023 |
| Mesos Consulting Limited | Professional & scientific | 2023 |
| Mess Around Limited | Other services | 2012 |
| Messam Construction Solutions Ltd | Construction | 2026 |
| Meta Golden Group Limited | Information & communication | 2024 |
| Meta International Group Ltd | Information & communication | 2024 |
| Meta Loop Films Limited | Information & communication | 2012 |
| Meta One Group Ltd | Information & communication | 2024 |
| Meta Prime Group Ltd | Information & communication | 2024 |
| Meta Silver Group Ltd | Wholesale & retail | 2024 |
| META24 Group Ltd | Information & communication | 2024 |
| Metal Card Company Limited | Extraterritorial | 2017 |
| Metal Gutter Manufacturers Association Limited | Other services | 2008 |
| Metamorphorces Ltd | Information & communication | 2025 |
| Metareno Ltd | Professional & scientific | 2024 |
| Metatrad Limited | Professional & scientific | 2008 |
| Metatron Group Ltd | Construction | 2024 |
| Metisian Ltd | Administrative & support | 2016 |
| Metistrad Ltd | Professional & scientific | 2025 |
| Metore Limited | Professional & scientific | 2020 |
| Metravyx Ltd | Information & communication | 2026 |
| Metro Supply Chain (PL UK) Limited | Real estate | 2017 |
| Metro Supply Chain (SCG UK) Limited | Financial services | 2022 |
| Metro Supply Chain (UK) Limited | Transport & logistics | 2006 |
| Metro Supply Chain Holdings (UK) Limited | Professional & scientific | 2016 |
| Metro Supply Chain Limited | Transport & logistics | 1997 |
| Metropolitan Infrastructure Limited | Administrative & support | 2006 |
| Metty Property Solutions Limited | Real estate | 2023 |
| Mewstone View Consulting Ltd | Professional & scientific | 2026 |
| MF Builders Limited | Construction | 2020 |
| Mfahk Ltd | Real estate | 2024 |
| MFC Contracting Limited | Construction | 1994 |
| MFP Holdings Limited | Financial services | 2020 |
| MG Elite Property Management Ltd | Real estate | 2026 |
| MG Musa Consulting Ltd | Professional & scientific | 2024 |