| Marjoram Holdings Ltd | Real estate | 2025 |
| Mark & JON Ltd | Real estate | 2013 |
| Mark Goldsmith Limited | Construction | 2026 |
| Mark J Biddle Ltd | Professional & scientific | 2022 |
| Mark Rainey Mortgages Ltd | Financial services | 2004 |
| Mark Westaway & SON (Horsehage) | | 2005 |
| Mark Your Packaging Ltd | Administrative & support | 2025 |
| Mark's Handyman and Van Ltd | Construction | 2023 |
| Market Wizards Ltd | Education | 2025 |
| Marketing 4 Everything Limited | Professional & scientific | 2025 |
| Marketing Angels (SW) Limited | Professional & scientific | 2015 |
| Marketing Evolved Ltd | Professional & scientific | 2011 |
| Marketing Geeks Ltd | Professional & scientific | 2017 |
| Marldon (Maple Leaf) Bowling Club Limited | Arts & recreation | 1994 |
| Marsden SW Ltd | Other services | 2005 |
| Marsden SW Property 2 Ltd | Financial services | 2026 |
| Martin BAX Organisation Limited | Real estate | 1977 |
| Martin Haycock Services Ltd | Construction | 2018 |
| Martin Rose Limited | Information & communication | 2002 |
| Martyn Kelland Coaching Ltd | Health & social care | 2024 |
| Mashford Property Investments Limited | Real estate | 2001 |
| Massey Building Management Ltd | Construction | 2007 |
| Massie Investments Ltd | Construction | 2021 |
| Maverick Aesthetics Ltd | Other services | 2025 |
| MAVERICK22 Limited | Wholesale & retail | 2024 |
| Mayfair Media Corporation Ltd | Professional & scientific | 2025 |
| Mayflower Lettings Ltd | Real estate | 2019 |
| Mccracken Consult Ltd | Construction | 2019 |
| Mccracken Developments Ltd | Construction | 2020 |
| Mcewan Associates Limited | Education | 2004 |
| MCM Partners Limited | Hospitality | 2018 |
| MCS Compliance Limited | Manufacturing | 2015 |
| MD Tapp Builders Limited | Construction | 2004 |
| Mdesign-Consultant Ltd | Wholesale & retail | 2023 |
| Meadcourt Residential Flats Limited | Households | 1985 |
| Medicine Woman Gathering Ltd | Arts & recreation | 2025 |
| Meek Lettings Ltd | Real estate | 2014 |
| Meetstop Ltd | Administrative & support | 2025 |
| Mellow Property Solutions Ltd | Real estate | 2024 |
| MEN Controls Ltd | Manufacturing | 2019 |
| Mental Monkey Ltd | Other services | 2019 |
| MEP Engineering and Expert Consultant Ltd | Professional & scientific | 2019 |
| Mermaid Mortgages Ltd | Financial services | 2022 |
| Mertbeliz Ltd | Hospitality | 2025 |
| Metatron International Limited | Other services | 2020 |
| MFS Southwest Ltd | Transport & logistics | 2025 |
| MFS Trucking Ltd | Extraterritorial | 2019 |
| MFV Amberlisa Limited | Agriculture & fishing | 2018 |
| MFV Ebonnie Limited | Agriculture & fishing | 2017 |
| MFV Heather K Limited | Agriculture & fishing | 2018 |
| MFV LA Creole II Ltd | Agriculture & fishing | 2014 |
| MG Biomass Plumbing & Heating Limited | Construction | 2018 |
| MG Education and Training Group Ltd | Other services | 2011 |
| MGF Tech Limited | Information & communication | 2023 |
| MGV Productions Ltd | Information & communication | 2010 |
| MI Bubble Ltd | Manufacturing | 2021 |
| Micro Engineering Consulting Limited | Professional & scientific | 2022 |
| Micro Plant South West Limited | Construction | 2016 |
| Micro Shure Limited | Other services | 2016 |
| Microbrand Watch Club Ltd | Wholesale & retail | 2022 |
| Microswift Ltd | Real estate | 2004 |
| Midas Mighty Ltd | Manufacturing | 2026 |
| Miechowicz Ltd | Health & social care | 2013 |
| MIL Property Holdings Ltd | Construction | 2019 |
| Milehouse Consultants Limited | Professional & scientific | 2017 |
| Milestone Collective Ltd | Wholesale & retail | 2024 |
| Milfords Amenity Limited | Households | 2007 |
| Millard Advisory Services Ltd | Professional & scientific | 2025 |
| Millbrook Steamboat and Trading Co.Limited(The) | Professional & scientific | 1929 |
| Millshill Recruitment Limited | Administrative & support | 2005 |
| Millward Consultancy Ltd | Professional & scientific | 2022 |
| Milvus Aviation Ltd | Transport & logistics | 2016 |
| Mindful Mountains Ltd | Administrative & support | 2016 |
| Mindready Solutions Ltd | Information & communication | 2009 |
| Mindscape Limited | Health & social care | 1999 |
| Mineral Digital Ltd | Professional & scientific | 2020 |
| Mini Vape Store Ltd | Wholesale & retail | 2026 |
| Minton Developments Limited | | 1988 |
| Mitchell SW Limited | Wholesale & retail | 2021 |
| MJ Newton Limited | Hospitality | 2024 |
| MJM (SW) Limited | Wholesale & retail | 2018 |
| MJS Assets Ltd | Real estate | 2026 |
| Mkjm Holdings Limited | Financial services | 2024 |
| Mmood Ltd | Transport & logistics | 2024 |
| Mod-Dec (South-West) Limited | Construction | 2004 |
| Modus Homes Ltd | Construction | 2022 |
| Mokki Ltd | Construction | 2020 |
| Monical Limited | Professional & scientific | 2022 |
| Monument AI Limited | Information & communication | 2025 |
| Moor Tors Manor Limited | Extraterritorial | 2005 |
| Moose(Bath) Limited | Wholesale & retail | 2015 |
| More Seafood Limited | Manufacturing | 2014 |
| Morgan Brooks Limited | Professional & scientific | 2019 |
| Morley Maverick Limited | Transport & logistics | 2010 |
| Morphing Ltd | Other services | 2019 |
| Moss Holdings (SW) Limited | Real estate | 2025 |
| Motorcycle Repair Torbay Ltd | Administrative & support | 2019 |
| MPQ Developments Limited | Transport & logistics | 2017 |
| MPQ Rentals Limited | Real estate | 2018 |
| MR & MR Hospitality Limited | Hospitality | 2021 |