| MAZ Trans Ltd | Transport & logistics | 2026 |
| Mazi Empire Ltd | Wholesale & retail | 2023 |
| Mazies Floristry Limited | Wholesale & retail | 2024 |
| MB Ashford Limited | Wholesale & retail | 2024 |
| MB Basildon Limited | Manufacturing | 2024 |
| MB Movers Ltd | Transport & logistics | 2024 |
| MB Staines Limited | Wholesale & retail | 2018 |
| MB4 Express Ltd | Wholesale & retail | 2018 |
| Mbelle Limited | Professional & scientific | 2024 |
| MBM Group Ltd | Construction | 2015 |
| MBM Haulage Ltd | Transport & logistics | 2026 |
| MC Electrical Services Ltd | Construction | 2017 |
| MC Home Property Management and Development Ltd | Real estate | 2017 |
| Mc'Jorge Limited | Real estate | 2023 |
| Mcbride Smith Limited | Real estate | 2019 |
| Mccollin Bryan Limited | Manufacturing | 2010 |
| MCE Visionconstruction Ltd | Construction | 2025 |
| Mcginty Contractors Ltd | Construction | 2007 |
| Mckops Move IT Limited | Water & waste | 2021 |
| MCL Construct Limited | Construction | 2016 |
| Mclovin Limited | Hospitality | 2016 |
| Mclovin Takeaway Limited | Hospitality | 2017 |
| MCM Acris Ltd | Construction | 2026 |
| Mcquean Supply Management Ltd | Professional & scientific | 2019 |
| MCW (Essex) Electrical Limited | Construction | 2023 |
| MD Construction & Design Ltd | Construction | 2015 |
| MD Dargis Construction Ltd | Construction | 2025 |
| Md&W Ltd | Construction | 2024 |
| MDC Real Estate Ltd | Real estate | 2023 |
| MDD Construction Ltd | Construction | 2019 |
| Mdrd Investments Ltd | Real estate | 2021 |
| Mead Electrical Services Ltd | Construction | 2018 |
| Mead VT Group Holdings Limited | Extraterritorial | 2014 |
| Mebyomotola Ltd | Health & social care | 2026 |
| MEC Consultancy Services (UK) Ltd | Construction | 2020 |
| Mechatronics Consulting Limited | Professional & scientific | 2015 |
| Medi Property Invest Ltd | Real estate | 2021 |
| Media Mayhem Ltd | Professional & scientific | 2015 |
| MEDIA365 Limited | Information & communication | 2013 |
| Medicin Ltd | Health & social care | 2019 |
| Medipath International Limited | Education | 2023 |
| Medisoma Ltd | Wholesale & retail | 2021 |
| Medo Cleaning Service Ltd | Administrative & support | 2015 |
| Medo Group Ltd | Transport & logistics | 2025 |
| Medtuyou Ltd. | Wholesale & retail | 2011 |
| Meehan Testing Solutions Ltd | Information & communication | 2022 |
| Meelumeelu Limited | Wholesale & retail | 2020 |
| Meesons Lane Management Company Limited | Households | 1989 |
| Meet to Aspire Limited | Information & communication | 2026 |
| Megan Mcloughlin Limited | Professional & scientific | 2021 |
| Megan Salmon-Ferrari Limited | Other services | 2021 |
| Megatrim Ltd | Wholesale & retail | 2012 |
| Megavston Limited | Professional & scientific | 2024 |
| Megawatts Electrical Services Ltd | Construction | 2026 |
| Mege Furniture Ltd | Construction | 2022 |
| Mehr N Properties Limited | Real estate | 2021 |
| Mehta Urology Ltd | Health & social care | 2016 |
| Meko Driver Ltd | Transport & logistics | 2017 |
| MEL998 Ltd | Wholesale & retail | 2024 |
| Mela Ngai Ltd | Manufacturing | 2022 |
| Melafel Ltd | Other services | 2023 |
| Mellett Ltd | Real estate | 2023 |
| Melodia Care Ltd | Public administration | 2024 |
| Melrose and Fellows Management Limited | Real estate | 2024 |
| Memi Services Limited | Information & communication | 2025 |
| MEMO1 Ltd | Construction | 2026 |
| Mended International Limited | Information & communication | 2026 |
| Mentores.Lt Ltd | Administrative & support | 2021 |
| Mentors After School Club Ltd | Education | 2020 |
| Mentors ASC | Education | 2019 |
| Merch Magic Ltd | Wholesale & retail | 2026 |
| Mercify UK Ltd | Health & social care | 2019 |
| Mercy Gold Limited | Health & social care | 2008 |
| Meridian Collection Ltd | Hospitality | 2025 |
| Merlin Components (London) Limited | Wholesale & retail | 1989 |
| Meronblue Limited | Real estate | 2006 |
| Mesa Grill Ltd | Hospitality | 2024 |
| Mesh-Iot Limited | Extraterritorial | 2015 |
| Mestre Delivery Company Limited | Transport & logistics | 2015 |
| MET Compliance Ltd | Professional & scientific | 2017 |
| MET5828 Limited | Professional & scientific | 2014 |
| Metal Partitions Ltd | Manufacturing | 2019 |
| Metalove Ltd | Manufacturing | 2019 |
| Metricwave Advertising Ltd | Professional & scientific | 2026 |
| Metro Rides Ltd | Transport & logistics | 2023 |
| MEZ Transport Ltd | Transport & logistics | 2019 |
| MF Hair Limited | Other services | 2024 |
| MG Construction LTU Limited | Construction | 2017 |
| MG Services General Ltd | Manufacturing | 2025 |
| MGH Façade Installation Ltd | Construction | 2019 |
| MGM Motors Ltd | Transport & logistics | 2018 |
| MGM Route 66 Ltd | Transport & logistics | 2016 |
| MGS Security Ltd | Other services | 2016 |
| MH1 Services Limited | Wholesale & retail | 2025 |
| MI26 Ltd | Arts & recreation | 2023 |
| Miagoods Ltd | Wholesale & retail | 2023 |
| Miah Estates Ltd | Real estate | 2019 |
| Mian & Brother Limited | Wholesale & retail | 2024 |
| Mian Traders Ltd | Administrative & support | 2017 |
| Mianzada Services Limited | Administrative & support | 2026 |