| Melt Better Ltd | Wholesale & retail | 2026 |
| Meltemhair Limited | Other services | 2022 |
| Melton Animal Centre Ltd | Agriculture & fishing | 2023 |
| Melz & Co Commercials Limited | Arts & recreation | 2022 |
| Melz & Co Investments Limited | Financial services | 2023 |
| Melz & Co Limited | Professional & scientific | 2018 |
| MEM DIY Ltd | Construction | 2022 |
| MEM Windows & Pergolas Ltd | Manufacturing | 2025 |
| MEM Windows Limited | Construction | 2017 |
| Member Benefits Ltd | Information & communication | 2017 |
| Memozan Ltd | Other services | 2020 |
| Mems Designs & Build Ltd | Professional & scientific | 2025 |
| Mems Properties Ltd | Real estate | 2022 |
| Memuzun Ltd | Administrative & support | 2026 |
| Men's Fitness & Nutrition Consultan's Ltd | Arts & recreation | 2021 |
| Men's Health Consultants Ltd | Other services | 2024 |
| Menad Express Limited | Hospitality | 2018 |
| Mend Grup Ltd | Construction | 2025 |
| Mene Holdings Group Ltd | Real estate | 2024 |
| Meneo Music Ltd | Information & communication | 2024 |
| Mensah & Co Ltd | Professional & scientific | 2008 |
| Mensarth Homes Limited | Real estate | 2025 |
| Mental H HUT CIC | Information & communication | 2024 |
| Mentexx Limited | Public administration | 2017 |
| Mentor by Design Ltd | Health & social care | 2022 |
| MEO Energy Solutions Ltd | Households | 2025 |
| Merc Education UK Limited | Professional & scientific | 2008 |
| Merc of Enfield Ltd | Wholesale & retail | 2022 |
| Mercedes Repair Centre Limited | Wholesale & retail | 2017 |
| Merchified Limited | Administrative & support | 2026 |
| Mercylane Solutions Ltd | Professional & scientific | 2026 |
| Merdo EN3 Limited | Wholesale & retail | 2026 |
| Meridian Energy and Construction Ltd | Construction | 2022 |
| Meridian Roofing & Property Services Ltd | Construction | 2025 |
| Meridianroutes Ltd | Administrative & support | 2024 |
| Meristan UK Ltd | Transport & logistics | 2015 |
| Merit Foods Ltd | Wholesale & retail | 2018 |
| Merit Manufacture Ltd | Manufacturing | 2025 |
| Merivale House Limited | Households | 1982 |
| Merrydine Limited | Hospitality | 2000 |
| Mersan Properties Ltd | Real estate | 2020 |
| Mert Limited | Wholesale & retail | 2003 |
| Mert's Jewellery Limited | Wholesale & retail | 2021 |
| Merthan Limited | Other services | 2020 |
| Mertranda Properties Limited | Real estate | 2024 |
| Merwan Ltd | Other services | 2024 |
| Merway Limited | Professional & scientific | 2001 |
| Meryne Care Ltd | Health & social care | 2024 |
| MES Food Ltd | Wholesale & retail | 2020 |
| Mesopotamia Construction Ltd | Construction | 2025 |
| Mess Food Ltd | Hospitality | 2026 |
| MET Accountancy Ltd | Professional & scientific | 2019 |
| MET Sports London Ltd | Arts & recreation | 2025 |
| Meta Cards Ltd | Wholesale & retail | 2026 |
| Metacosm Ltd | Financial services | 2022 |
| Metal Fabrications Ltd | Manufacturing | 2018 |
| Metaspheric Ltd | Professional & scientific | 2022 |
| Metehan Shop Ltd | Wholesale & retail | 2025 |
| Method Photo Limited | Information & communication | 2015 |
| Metro Chicken & Meat Limited | Wholesale & retail | 2011 |
| Metro Floral Design Limited | Other services | 2011 |
| Metro Meats Limited | Wholesale & retail | 2005 |
| Metroaxs Ltd | Information & communication | 2025 |
| Metrotag Ltd | Wholesale & retail | 2026 |
| Mets Hair Limited | Other services | 2014 |
| Mettro Limited | Wholesale & retail | 2022 |
| Mexman UK Ltd | Hospitality | 2025 |
| Meyla Group Investment Ltd | Real estate | 2024 |
| Mezre Limited | Financial services | 2026 |
| MFX Group Ltd | Wholesale & retail | 2025 |
| MG Services and Solutions Limited | Health & social care | 2023 |
| MG Sweets and Wines Ltd | Wholesale & retail | 2026 |
| MGA Medical Services Ltd | Professional & scientific | 2012 |
| Mgeo Ltd | Wholesale & retail | 2024 |
| MGH Academy Ltd | Education | 2024 |
| MGL Digital Media Ltd | Professional & scientific | 2024 |
| Mglc Taxi Ltd | Construction | 2018 |
| Mglcl Limited | Wholesale & retail | 2021 |
| MGM Engineering and Consultancy Ltd | Professional & scientific | 2020 |
| MH Auto Group Ltd | Administrative & support | 2024 |
| MH Car Electric Ltd | Wholesale & retail | 2026 |
| MH Grooming Ltd | Other services | 2020 |
| MHE Accountancy Ltd | Professional & scientific | 2024 |
| MHJ Corp Ltd | Administrative & support | 2024 |
| MHR Lettings Ltd | Real estate | 2024 |
| MI Amore London Ltd | Wholesale & retail | 2020 |
| MI Digital LAB Ltd | Wholesale & retail | 2019 |
| MIA 68 Limited | Other services | 2017 |
| MIA Fruit & VEG Ltd | Transport & logistics | 2019 |
| MIA PUB Ltd | Financial services | 2024 |
| Miaccountant & LBA Limited | Professional & scientific | 2006 |
| Miaccountant Limited | Other services | 2013 |
| Miahcorp Estates Ltd | Real estate | 2024 |
| Miahcorp Foods Ltd | Manufacturing | 2026 |
| Mial Prestige Trade Ltd | Construction | 2023 |
| Miasa Ltd | Real estate | 2022 |
| Mica Enterprises Ltd | Hospitality | 2020 |
| Micey Ltd | Hospitality | 2025 |
| Michael and James Property Ltd | Real estate | 2026 |
| Michael O'Connor Holdings Limited | Construction | 1985 |