| Margaret Campbell Enterprises Ltd | Financial services | 2025 |
| Margetts & Walker Construction Limited | Construction | 2019 |
| Margot's Farm Ltd | Agriculture & fishing | 2025 |
| Marina Bristol Ltd | Health & social care | 2015 |
| Mario Bathroom Installer Ltd | Construction | 2020 |
| Mark B Taylor Limited | Professional & scientific | 2019 |
| Mark Butterfield Furniture Limited | Manufacturing | 2005 |
| Mark Devine Medicolegal Ltd | Professional & scientific | 2022 |
| Mark Harris Upholstery Limited | Other services | 2008 |
| Mark Mcclure Studio Ltd. | Administrative & support | 2007 |
| Mark Moor Metals Ltd. | Wholesale & retail | 2024 |
| Mark Peters Electrical Limited | Construction | 2012 |
| Mark Pritchard Design Limited | Professional & scientific | 2011 |
| Mark Roden Properties Limited | Real estate | 2005 |
| Mark Stancer Limited | Wholesale & retail | 2016 |
| Markan Properties Limited | Real estate | 2019 |
| Market Quarter (Hatherleigh) Management Company Limited | Households | 2020 |
| Marketing Know-How Ltd. | Professional & scientific | 2015 |
| Marks Builders and Carpentry Ltd | Construction | 2017 |
| Marland Limited | Real estate | 2020 |
| Marmaris Kebab(Taunton) Ltd | Hospitality | 2019 |
| Marmaris Pizza House Ltd | Hospitality | 2025 |
| Marmos Fast Delivery Ltd | Transport & logistics | 2020 |
| Marran Properties (Cornwall) Limited | Real estate | 2019 |
| Marsh Farm Estates Limited | Construction | 2026 |
| Marshalsea Engineering Limited | Professional & scientific | 2019 |
| Marshfield House (Minehead) Limited | Households | 2003 |
| Martan Trading Limited | Hospitality | 2002 |
| Martec Holdings Limited | Education | 1996 |
| Martec International Limited | Information & communication | 1988 |
| Martial Arts Equipment UK Ltd | Wholesale & retail | 2009 |
| Martin Cash Limited | Construction | 2012 |
| Martin Cocks Angling Supplies Limited | Wholesale & retail | 2006 |
| Martin Haskett Agricultural Contractors Ltd | Agriculture & fishing | 2002 |
| Martinmy Limited | Wholesale & retail | 2026 |
| Martock Minibuses Limited | Administrative & support | 2015 |
| Martyn Grellier Limited | Construction | 2013 |
| Marvelle Ltd | Administrative & support | 2010 |
| Marwan Interiors Ltd | Construction | 2022 |
| Mary's Nifty Solutions Ltd | Construction | 2021 |
| MAS Partners Ltd | Professional & scientific | 2024 |
| Masala BOT Ltd | Hospitality | 2024 |
| Mash Group Ltd | Administrative & support | 2011 |
| Masiff Interiors Ltd | Professional & scientific | 2016 |
| Maskgraphics Limited | Information & communication | 2003 |
| Masons Arms Management Limited | Real estate | 2007 |
| Masra Properties Limited | Real estate | 2018 |
| Mass Automotive Limited | Wholesale & retail | 2026 |
| Mass Care Momentous Ltd | Administrative & support | 2016 |
| Mass Logistics Solutions Ltd | Transport & logistics | 2017 |
| Mastergen Ltd | Agriculture & fishing | 2014 |
| Mastergleam Commercial Cleaning Services Ltd | Other services | 1995 |
| Masterplumb Limited | Construction | 2005 |
| Mastertile (South West) Limited | Construction | 2018 |
| Mastervend SW Limited | Other services | 2015 |
| Mastolux Limited | Wholesale & retail | 2023 |
| Mata PA Hamba Ltd | Professional & scientific | 2025 |
| Material Movements Limited | Transport & logistics | 2012 |
| Matotwe Ltd | Construction | 2017 |
| Matravers Engineering Limited | Manufacturing | 1990 |
| Matt Frost Ltd | Professional & scientific | 2012 |
| Matt Kirk Consultancy Ltd | Professional & scientific | 2026 |
| Mattancherry Ltd | Hospitality | 2019 |
| Matthew Cookson Ltd | Wholesale & retail | 2013 |
| Matthew Jonathan Paterson Limited | Health & social care | 2014 |
| Matthews Electrical Services South West Limited | Construction | 2015 |
| Mattocks Green Enterprises Ltd | Professional & scientific | 2022 |
| Mattox Limited | Information & communication | 2024 |
| Matvec Ltd | Information & communication | 2020 |
| Maura Properties SW Ltd | Real estate | 2024 |
| Mauve Stripe Limited | Construction | 2026 |
| Mayetta Limited | Information & communication | 2018 |
| Mayfair Plumbing & Heating Limited | Construction | 2016 |
| Mayland Fruit Farms (Wellington) Limited | Extraterritorial | 1932 |
| Mayne Investments Limited | Real estate | 1997 |
| Maze Networks Limited | Professional & scientific | 2015 |
| MB Solar Cleaning Limited | Administrative & support | 2022 |
| MB Tree Services Limited | Construction | 2016 |
| Mbatex Ltd | Administrative & support | 2025 |
| MBR Capital Ltd | Real estate | 2020 |
| MBS Farriers Limited | Administrative & support | 2008 |
| Mcarthur Consultancy Limited | Professional & scientific | 2023 |
| Mcdermott & Simpson Ltd | Financial services | 2026 |
| Mcdiamond Solutions Limited | Education | 2010 |
| Mcdn Strategies & Operations Limited | Professional & scientific | 2023 |
| Mcdowall Vending Co. Ltd | Wholesale & retail | 2026 |
| Mckenna Property (Taunton) Limited | Real estate | 2014 |
| Mcmahon & West Limited | Real estate | 2019 |
| MCT Reman Limited | Manufacturing | 2009 |
| MD Consult Limited | Professional & scientific | 2011 |
| MD Jeycare Limited | Real estate | 2024 |
| MD Property (Taunton) Limited | Real estate | 2024 |
| MEA Sales & Marketing Limited | Wholesale & retail | 2004 |
| Mead Farm Foods Ltd | Manufacturing | 2016 |
| Mead Park Limited | Agriculture & fishing | 2016 |
| Meadow LEE Holiday Park Ltd | Hospitality | 2015 |
| Meadow Somerset Limited | Hospitality | 2025 |
| Meadowside (Somerset) Ltd | Health & social care | 2026 |
| Meare Court Ltd | Hospitality | 2019 |
| Meat Link (South West) Limited | Professional & scientific | 2008 |