| Mediqa Limited | Health & social care | 2019 |
| Mediterranean Restaurants (UK) Limited | Hospitality | 2010 |
| Mediumz Ltd | Manufacturing | 2004 |
| Medlife Medical Ltd | Health & social care | 2024 |
| Medoc Management Limited | Households | 1992 |
| Medrehab Services Ltd | Health & social care | 2025 |
| Medsham Ltd | Professional & scientific | 1998 |
| Medsolutions (Europe) Limited | Manufacturing | 2015 |
| Medusa Catering Ltd | Hospitality | 2018 |
| Medusa Welding Services Ltd | Manufacturing | 2002 |
| Medwells Committed Solutions Ltd | Public administration | 2025 |
| Medz BB Limited | Other services | 2012 |
| Meer Capital Limited | Real estate | 2025 |
| Meera Nivas Ltd | Real estate | 2021 |
| Meerham Limited | Wholesale & retail | 2020 |
| Meerzorg Design Limited | Administrative & support | 2012 |
| Mega Interbuild Ltd | Construction | 2016 |
| Mega Management Services Ltd | Administrative & support | 2014 |
| Mega Properties Limited | Real estate | 2024 |
| Mega Service Providers Ltd | Information & communication | 2024 |
| Megaforce Limited | Extraterritorial | 1984 |
| Meghen & Co Limited | Other services | 2020 |
| Megway Logistics Ltd | Transport & logistics | 2020 |
| Megway Parcels Ltd | Transport & logistics | 2022 |
| Mehajsameer Ltd | Real estate | 2025 |
| Mehmet Real Estate Ltd | Construction | 2025 |
| Melanie Day Limited | Other services | 2003 |
| Meld Services Limited | Health & social care | 2015 |
| Melia Food Ltd | Wholesale & retail | 2024 |
| Melian Logistic Limited | Transport & logistics | 2018 |
| Melisa Ltd | Real estate | 2022 |
| Melissa Francois Ravalier Ltd | Professional & scientific | 2016 |
| Mell Interiors Ltd | Construction | 2019 |
| Mella Clinic Limited | Other services | 2024 |
| Melluish Bros. Limited | Manufacturing | 1961 |
| Melting Memories Limited | Hospitality | 2023 |
| Melvic Trade Ltd | Wholesale & retail | 2025 |
| Melvlaville & Company Limited | Real estate | 2024 |
| Memento Exclusives Limited | Manufacturing | 2010 |
| Memon Property Management Ltd | Real estate | 2023 |
| Memories and Gifts Ltd | Wholesale & retail | 2015 |
| Memory Gifts Ltd | Manufacturing | 2016 |
| Memseed Limited | Information & communication | 2024 |
| Memwa Solutions Limited | Administrative & support | 2026 |
| Men's Shopping Ltd | Professional & scientific | 2021 |
| Menace Media Ltd | Information & communication | 2021 |
| Menacraft Limited | Hospitality | 2002 |
| Menajud Limited | Health & social care | 2014 |
| Mendstacks SOL Ltd | Wholesale & retail | 2025 |
| Menicon Limited | Manufacturing | 1972 |
| Mental Wealth Collective CIC | Health & social care | 2025 |
| Mental Wellbeing Limited | Health & social care | 2015 |
| Mentaur Community Support Limited | Health & social care | 2007 |
| Mentaur Limited | Health & social care | 1988 |
| Mentley Farms LP | | 2024 |
| Mentor Merlin UK Ltd | Information & communication | 2021 |
| Mentoringmax Consultancy Ltd | Real estate | 2023 |
| Mepko Ltd | Wholesale & retail | 2024 |
| Meraki Spmu and Beauty Limited | Education | 2023 |
| Meraz Takeaway Ltd | Hospitality | 2017 |
| Mercedes SLK Freight Limited | Transport & logistics | 2025 |
| Mercedes Van Services Ltd | Manufacturing | 2025 |
| Merchandising for YOU Limited | Wholesale & retail | 2014 |
| Merchandising Systems Solutions Ltd | Manufacturing | 2010 |
| Merci Conglomerate Ltd | Administrative & support | 2025 |
| Mercia Orthodontics Ltd | Health & social care | 2019 |
| Mercurial Diagnostic Imaging Limited | Health & social care | 2025 |
| Mercury Dynamics Ltd | Information & communication | 2023 |
| Mercury Food Services Ltd | Wholesale & retail | 2024 |
| Mercury Sloane Investments Limited | Financial services | 2019 |
| Mere Property Limited | Real estate | 2016 |
| Mereacre M & G Limited | Transport & logistics | 2013 |
| Mereway Butterfly PRE School Ltd | Education | 2010 |
| Merge Residential Limited | Real estate | 2017 |
| Merger Services Limited | Administrative & support | 2014 |
| Meridian Care Ltd | Health & social care | 2022 |
| Meridian Cleaning Group Ltd | Administrative & support | 2026 |
| Meridian Land Ltd | Construction | 2010 |
| Merisma Ltd | Information & communication | 2019 |
| Merit Scaffolding Ltd | Construction | 2024 |
| Merkonidis Ltd | Health & social care | 2021 |
| Merlin Process Software Limited | Information & communication | 2007 |
| Merquen Real Estate Ltd | Real estate | 2025 |
| Merquen Shop Ltd | Wholesale & retail | 2023 |
| Merquen Unisex Salon Ltd | Other services | 2023 |
| Merrick Construction Services Limited | Construction | 2008 |
| Merryfield Estates Limited | Wholesale & retail | 2015 |
| Mesco Solutions Limited | Construction | 2015 |
| Meshvista Limited | Real estate | 2025 |
| Meshwork-Technik Ltd | Professional & scientific | 2023 |
| Mesina Auto Ltd | Extraterritorial | 2019 |
| Messageday Limited | Professional & scientific | 2001 |
| Messenger Cast Stone & Concrete Products Ltd. | Extraterritorial | 2013 |
| Messiah Corporation Limited | Administrative & support | 2003 |
| Mesters' Market Limited | Wholesale & retail | 2024 |
| MET Management Solutions Limited | Professional & scientific | 2008 |
| Metafibre.Co.Uk Ltd | Information & communication | 2023 |
| Metal Centre Limited | Manufacturing | 1983 |
| Metal Collection LTS Ltd | Other services | 2025 |
| Metal Time Ltd | Manufacturing | 2021 |