| MAT Construct Ltd | Construction | 2026 |
| Matching Land Limited | Administrative & support | 2014 |
| Mateas Ltd | Construction | 2021 |
| Matipo Arts CIC | Education | 2021 |
| Matt Stent Ltd | Information & communication | 2023 |
| Matthew's Plants Ltd | Agriculture & fishing | 2022 |
| Matthews Haulage & Partners LLP | | 2021 |
| Matthews Haulage Limited | Transport & logistics | 1975 |
| Matti Care Limited | Health & social care | 2022 |
| Matwill Wealth Management Ltd | Professional & scientific | 2023 |
| Maureen Eleanor Powell Ltd | Extraterritorial | 2022 |
| Mauroxy Properties Ltd | Real estate | 2025 |
| Maven Investment Limited | Real estate | 2021 |
| MAX Cars Ltd | Wholesale & retail | 2025 |
| MAX Exposure Ltd | Professional & scientific | 2022 |
| MAX Fit Pro Ltd | Manufacturing | 2024 |
| MAX Ukhome Ltd. | Real estate | 2023 |
| Maximvs Health Ltd. | Health & social care | 2018 |
| Maxord Consultancy Services Ltd | Other services | 2024 |
| Maxord Technical Services Ltd | Other services | 2024 |
| Maxzara (UK) Limited | Wholesale & retail | 2012 |
| MAY AIY Limited | Professional & scientific | 2024 |
| MAY and Gill Global Resource Limited | Health & social care | 2019 |
| Maya Holdings PVT Ltd | Manufacturing | 2025 |
| Maybelle Ltd | Construction | 2024 |
| Maybury Court Management (Ealing) Limited | Households | 1972 |
| Maydas Healthcare Ltd | Health & social care | 2021 |
| Maydas Properties Limited | Real estate | 2021 |
| Maydichi Limited | Real estate | 2023 |
| Mayfair Court (Derby) Co. Limited | Real estate | 2018 |
| Mayfield Farm Bakery Limited | Manufacturing | 2012 |
| Mayflower Rise Over Norton Limited | Households | 2021 |
| Mayhew Fitness Innovations Limited | Manufacturing | 2025 |
| Maymae Limited | Professional & scientific | 2021 |
| Maymana Ltd | Real estate | 2021 |
| Mayrom Ltd | Health & social care | 2026 |
| MAZ Property Holdings Ltd | Real estate | 2020 |
| Mazalo Ltd | Health & social care | 2023 |
| Mazztech Limited | Information & communication | 2020 |
| MB Membranes Limited | Construction | 2015 |
| MB NAV Consultancy Services Ltd | Information & communication | 2018 |
| MB UK Auto Electrical Limited | Wholesale & retail | 2022 |
| MBB Trading Limited | Wholesale & retail | 2015 |
| MBH Collective Ltd | Wholesale & retail | 2026 |
| Mbill Ltd | Information & communication | 2020 |
| Mccollins International Limited | Other services | 2018 |
| MCF Financial Consultancy Ltd | Professional & scientific | 2020 |
| Mcguckin Plant Hire Limited | Construction | 1970 |
| Mckellar & Sons Removal & Storage Limited | Transport & logistics | 2008 |
| Mckenzie Arnold Group Ltd | Other services | 2015 |
| Mckenzie Friends UK Support Ltd | Administrative & support | 2026 |
| MCL Law Limited | Professional & scientific | 2026 |
| Mcp&Tm Services Ltd | Professional & scientific | 2026 |
| MCS Stonecare Limited | Administrative & support | 2009 |
| Mcvicar Aviation Limited | Manufacturing | 2022 |
| MD Glass Partitions Limited | Construction | 2018 |
| MD Safety Solutions Ltd | Financial services | 2022 |
| MDC Work Surfaces Limited | Construction | 2013 |
| MDL Glazing Ltd | Financial services | 2024 |
| MDM Autos Ltd | Wholesale & retail | 2025 |
| MDP Services (Southern) Ltd | Other services | 2017 |
| ME Pegasus Props Ltd | Arts & recreation | 2016 |
| Mead Testing Ltd | Professional & scientific | 2002 |
| Meadow Projects Ltd | Construction | 2021 |
| Meas Services Limited | Health & social care | 2024 |
| Meaty Solutions Ltd | Information & communication | 2015 |
| MEB Coffee Limited | Hospitality | 2025 |
| MEC 5.1 Ltd | Hospitality | 2024 |
| MEC5 Ltd | Real estate | 2018 |
| Med-Chaservices Ltd | Health & social care | 2019 |
| Med-First Care Limited | Health & social care | 2022 |
| Medbury Medical Services UK Ltd | Health & social care | 2021 |
| Medcom Personnel Ltd | Health & social care | 2011 |
| Medi Mobile-Uk Limited | Health & social care | 2016 |
| Mediatechinvision Ltd | Professional & scientific | 2022 |
| Medicale Group Ltd | Health & social care | 2021 |
| Medicrew Services Limited | Health & social care | 2018 |
| Mediplumb Ltd | Construction | 2026 |
| Medivita Ltd | Health & social care | 2025 |
| Medspart Limited | Health & social care | 2025 |
| MEE Sushi Ltd | Hospitality | 2023 |
| Meebest Healthcare Ltd | Education | 2018 |
| Megas Holdings CIC | Real estate | 2026 |
| Megatouring Ltd | Arts & recreation | 2024 |
| Meinert Corporation Ltd | Administrative & support | 2010 |
| Melade Limited | Administrative & support | 2025 |
| Mele Freight Ltd | Transport & logistics | 2022 |
| Mello Properties Ltd | Real estate | 2024 |
| Melmil Ltd | Health & social care | 2023 |
| Membley Limited | Health & social care | 2015 |
| Membrane Management Services Ltd | Real estate | 2022 |
| Memento-Trading Ltd | Wholesale & retail | 2022 |
| Memzhairandbeauty Ltd | Other services | 2021 |
| Menssun Medical Services Limited | Health & social care | 2023 |
| Menutech Solutions Limited | Information & communication | 2025 |
| Menyi Steele 2 Limited | Real estate | 2025 |
| Menyi Steele 3 Limited | Real estate | 2026 |
| Menyi Steele Limited | Construction | 2024 |
| Merchant Agencies Limited | Professional & scientific | 2017 |
| Mercy Health Care Ltd | Health & social care | 2014 |