| Mcmurdie Heating & Energy Ltd | Construction | 2011 |
| Mcmurdie Plumbing & Maintenance Ltd | Construction | 2015 |
| MCP Electrical Services Limited | Construction | 2015 |
| MD Ventures Limited | Professional & scientific | 2012 |
| MDG Property Maintenance Ltd | Construction | 2025 |
| ME and Sons Catering Ltd | Hospitality | 2025 |
| Me&Lh Services Ltd | Construction | 2023 |
| Meal UP Limited | Hospitality | 2023 |
| MEC London Limited | Construction | 2005 |
| Medco Commercial Management Limited | Professional & scientific | 2020 |
| Media News Times Ltd | Information & communication | 2022 |
| Medics AZ Ltd | Health & social care | 2023 |
| Mediterraneo Capital International Ltd | Professional & scientific | 2020 |
| Mediterraneo-Capital Ltd | Other services | 2019 |
| Medlogix Limited | Health & social care | 2001 |
| MEE & SON Trading Ltd | Administrative & support | 2023 |
| Megh's Kitchen Ltd | Hospitality | 2021 |
| Megik Events Limited | Administrative & support | 2022 |
| Megik Ltd | Administrative & support | 2021 |
| Meisheng Shipping Services Co., Ltd. | Extraterritorial | 2019 |
| MEL Gaynor Music Ltd | Information & communication | 2022 |
| Melinda Fashion United Clothes Company Limited | Wholesale & retail | 2023 |
| Melio Records Ltd | Information & communication | 2025 |
| Meliora 67 Limited | Professional & scientific | 2021 |
| Meliora Property Investments Ltd | Real estate | 2022 |
| Melisi Limited | Hospitality | 2015 |
| Mem's Cafe Limited | Hospitality | 2014 |
| Mentor Investments Limited | Real estate | 2017 |
| Meporosu Limited | Real estate | 2015 |
| Meraj E Business Ltd | Professional & scientific | 2023 |
| Meramax Properties Management Ltd | Real estate | 2013 |
| Meridian Crest Property Ltd | Real estate | 2026 |
| Merie BIN Mahfouz Company (UK) Limited | Real estate | 1982 |
| Merkurum Ltd | Construction | 2025 |
| Merriment Homes Ltd | Real estate | 2015 |
| Merson Ltd | Hospitality | 2024 |
| Merthyr Properties Ltd | Real estate | 2016 |
| MES Holdings Group Ltd | Real estate | 2018 |
| MES Investments Limited | Real estate | 2016 |
| Mesan Electric Ltd | Wholesale & retail | 2023 |
| Metaglobe Labs Ltd | Information & communication | 2019 |
| Metal Construct Ltd | Construction | 2026 |
| Metal Promotional Ltd | Manufacturing | 2020 |
| Metasuperfoods Ltd | Wholesale & retail | 2019 |
| Metech Ltd | Information & communication | 2024 |
| Metech Solutions Ltd | Wholesale & retail | 2026 |
| Meva Telematics Ltd | Manufacturing | 2026 |
| Mews 'N' Barks LLP | | 2023 |
| Mexicroft Limited | Transport & logistics | 2017 |
| Mexmoor Limited | Extraterritorial | 2018 |
| Mezcali Limited | Wholesale & retail | 2008 |
| MF Drylining Ltd | Construction | 2023 |
| Mfhz Properties Limited | Real estate | 2020 |
| Mfrml Limited | Professional & scientific | 2004 |
| MG & Family Ltd | Information & communication | 2008 |
| MG Construction Middlesex Limited | Construction | 2017 |
| MG Little Bees Limited | Health & social care | 2024 |
| MG Testing Solutions Ltd | Professional & scientific | 2021 |
| Mg&F Properties Limited | Real estate | 2025 |
| MG2M Construction Ltd | Construction | 2023 |
| MGC Limited Company Ltd | Construction | 2019 |
| MGH Roofing & Building Contractors Ltd | Construction | 2023 |
| MGL Interiors Limited | Construction | 2007 |
| Mgrd Ltd | Information & communication | 2026 |
| MH Human Capital Ltd | Administrative & support | 2024 |
| MHU Catering Ltd | Hospitality | 2022 |
| MHU Homes Ltd | Real estate | 2026 |
| MIA Molato Architects Ltd | Professional & scientific | 2020 |
| MIA Pietra Ltd | Wholesale & retail | 2025 |
| Miamy Nutrition Ltd | Other services | 2018 |
| Mick R’S Ltd | Wholesale & retail | 2024 |
| Mictan Holdings Limited | Real estate | 2021 |
| Midco Enterprise 2 Limited | Financial services | 2023 |
| Midco Enterprise Limited | Financial services | 2023 |
| Middlesex Cleaning Services Limited | Other services | 2019 |
| Middlesex County Football Association Limited | Arts & recreation | 2003 |
| Middlesex Stadium Limited | Real estate | 2007 |
| Midland OIL Recycling Ltd | Water & waste | 2020 |
| Midlands First Security Ltd | Administrative & support | 2022 |
| Midlands Training and Consultancy Services Ltd | Education | 2020 |
| Midnight Heating Ltd | Construction | 2017 |
| Midnight LAB Ltd | Manufacturing | 2025 |
| Mifa UK. Limited | Financial services | 2006 |
| Migrant Children's Foundation | Professional & scientific | 2010 |
| Migz Ltd | Professional & scientific | 2025 |
| Mikes Paving & Landscaping Limited | Construction | 2019 |
| Milanda Ltd | Manufacturing | 2019 |
| Mile-Ex Capital UK Limited | Financial services | 2025 |
| Mill Lane Project Limited | Construction | 2016 |
| Mimapay Ltd | Professional & scientific | 2019 |
| MIN & Mich Ltd | Wholesale & retail | 2020 |
| Mina Clinic Limited | Health & social care | 2026 |
| Mind Music Ltd | Information & communication | 2014 |
| Mindful Yoga Limited | Arts & recreation | 2010 |
| Mindkin Ltd | Professional & scientific | 2024 |
| Mindsport Limited | Health & social care | 2007 |
| Minerva Mediation Ltd | Professional & scientific | 2011 |
| Mingchuang Metals Co., Ltd | Administrative & support | 2023 |
| Mingxing Crafts Co., Ltd | Administrative & support | 2019 |
| Mini India the Grocers Ltd | Wholesale & retail | 2020 |