| Martlands Waste Solutions Ltd | Water & waste | 2009 |
| Marty's Cafe Limited | Hospitality | 2025 |
| Martyn Collis Trading Limited | Professional & scientific | 2017 |
| Maru Limited | Hospitality | 2019 |
| Marutombole Ltd | Wholesale & retail | 2022 |
| Marvel Electronics Ltd | Manufacturing | 2025 |
| Marvel Knight Ltd | Transport & logistics | 2022 |
| Marvell Training & Development & Consultancy Services Limited | Administrative & support | 2006 |
| Marvelous Studio Ltd | Wholesale & retail | 2021 |
| Marven Trading Limited | Wholesale & retail | 2019 |
| Marvic Builders Limited | Construction | 2025 |
| Marvin VFX Ltd | Information & communication | 2021 |
| Marvio Green Ltd | Construction | 2018 |
| Marx Insurance Services Limited | Financial services | 1986 |
| Mary Austin Associates Ltd | Other services | 2015 |
| Mary Bedford Ltd | Professional & scientific | 2021 |
| Mary Joy Cruiz Ltd | Professional & scientific | 2024 |
| Mary Kate Property Management Limited | Real estate | 2013 |
| Mary Margaret Mackie Trading Limited | Agriculture & fishing | 2015 |
| Mary Mary Floral Design Limited | Wholesale & retail | 2021 |
| Mary N Smyth Ltd | Professional & scientific | 2023 |
| Maryanji Medical Limited | Health & social care | 2015 |
| Marybone Youth & Community Association Limited | Other services | 1997 |
| Maryholm Trading Limited | Professional & scientific | 2015 |
| Maryland Bidco Limited | Financial services | 2022 |
| Maryland Carehome Ltd | Health & social care | 2009 |
| Maryvale Nurseries (Holdings) Limited | Financial services | 2019 |
| Maryvale Nurseries Ltd | Education | 2003 |
| Marzipan Marketing Ltd | Professional & scientific | 2024 |
| MAS Cosmetics Ltd | Wholesale & retail | 2025 |
| MAS Financial Services Limited | Professional & scientific | 2024 |
| MAS International Education Services Limited | Education | 2022 |
| Masakeen Express Limited | Hospitality | 2026 |
| Masaken Limited | Households | 2024 |
| MASC4MASKS Limited | Wholesale & retail | 2020 |
| Masda Gym Liverpool Limited | Arts & recreation | 2025 |
| Mase Build Ltd | Real estate | 2025 |
| Mase Projects Ltd | Real estate | 2024 |
| Maslen Asset Management Limited | Real estate | 1963 |
| Mason & Partners Limited | Real estate | 1993 |
| Mason Alexander Property Consultancy Ltd | Real estate | 2019 |
| Mason Bibby 1981 Trust | Professional & scientific | 2020 |
| Mason Finch Ltd | Administrative & support | 2023 |
| Mason Freeport Ltd | Transport & logistics | 2021 |
| Mason Owen & Partners Limited | Real estate | 1979 |
| Mason Owen (Specialist Risks) Limited | Extraterritorial | 2013 |
| Mason Owen Financial Services (Wirral) Ltd | Extraterritorial | 1985 |
| Mason Owen Financial Services Limited | Financial services | 1988 |
| Mason Owen Nominees One Limited | Professional & scientific | 2019 |
| Mason Owen Nominees Two Limited | Professional & scientific | 2019 |
| Mason Partners LLP | | 2012 |
| Mason Property Holdings Ltd | Real estate | 2020 |
| Mason Verdi Holdings Ltd | Real estate | 2021 |
| Mason Verdi Ltd | Real estate | 2017 |
| Mason Wright Associates Ltd | Professional & scientific | 2016 |
| Mason-Wade Developments Ltd | Real estate | 2019 |
| Masonic Real Estate Ltd | Real estate | 2022 |
| Masons Building RTM Company Ltd | Real estate | 2015 |
| Masons Cleaning Services Ltd | Administrative & support | 2024 |
| Masons Paviors Ltd | Construction | 2016 |
| Masons Properties NW Limited | Real estate | 2024 |
| Mason’S Media Ltd | Professional & scientific | 2024 |
| Mass International Group Ltd | Manufacturing | 2022 |
| Mass Nutrition Ltd | Manufacturing | 2026 |
| Massage Store Ltd | Wholesale & retail | 2008 |
| Massala House Ltd | Hospitality | 2024 |
| Massey Coldbeck Engineering Ltd | Manufacturing | 2002 |
| Massey Coldbeck Limited | Wholesale & retail | 1980 |
| Massie Properties (North West) Ltd | Real estate | 2019 |
| Massimì Ltd | Hospitality | 2025 |
| Masstrax Music Ltd | Arts & recreation | 2010 |
| Mast Group Limited | Manufacturing | 1959 |
| Mastab Ltd | Wholesale & retail | 2024 |
| Master a Ltd | Education | 2025 |
| Master Academy Ltd | Professional & scientific | 2016 |
| Master AD Ltd | Professional & scientific | 2014 |
| Master Class (Liverpool) Limited | Arts & recreation | 2012 |
| Master Concrete (Northern) Limited | Manufacturing | 2014 |
| Master Installs Ltd | Construction | 2024 |
| Master KIT Limited | Administrative & support | 2017 |
| Master Prep Ltd | Hospitality | 2018 |
| Masterbau Patrycja Chlebowicz Ltd | Wholesale & retail | 2025 |
| Mastercraft Limited | Administrative & support | 2022 |
| Masterplan Holdings Ltd | Real estate | 2024 |
| Masters Costs Consultants Ltd | Professional & scientific | 1997 |
| MAT Care Limited | Administrative & support | 2016 |
| Matalan AF Limited | Financial services | 2021 |
| Matalan Direct Limited | Wholesale & retail | 2013 |
| Matalan Finance PLC | Financial services | 2006 |
| Matalan Holding Company Limited | Financial services | 2001 |
| Matalan Investments Limited | Financial services | 2001 |
| Matalan Limited | Financial services | 1981 |
| Matalan Retail Ltd. | Wholesale & retail | 1987 |
| Matalan Travel Limited | Administrative & support | 2001 |
| Matames Ltd | Information & communication | 2025 |
| Matanda Equestrian Ltd | Wholesale & retail | 2019 |
| Matars Fast Food Ltd | Hospitality | 2023 |
| Matars Ltd | Other services | 2019 |
| Match Day Prints Limited | Wholesale & retail | 2025 |
| Match Fit Catering Limited | Hospitality | 2017 |