| Manor Building Company (Torbay) Limited | Construction | 2015 |
| Manor House Offices Limited | Real estate | 2023 |
| Manor Self Storage Ltd | Administrative & support | 2022 |
| Manson Guitar Works Limited | Manufacturing | 2013 |
| Manteion Limited | Professional & scientific | 2005 |
| Mantracom Limited | Wholesale & retail | 2011 |
| Manuell Properties Ltd | Real estate | 2018 |
| Maple Green Property Limited | Real estate | 2018 |
| Marathon Taxis Limited | Transport & logistics | 2016 |
| Marble Mosaic Company Limited(The) | Construction | 1923 |
| March Golf Academy Limited | Wholesale & retail | 2025 |
| Margoux Limited | Hospitality | 2019 |
| Marhamchurch Antiques Limited | Wholesale & retail | 2013 |
| Mariners Limited | Real estate | 2003 |
| Maritime AMC Limited | Other services | 2016 |
| Mark Ford Builders Limited | Construction | 2009 |
| Mark II Builders and Bar Fitters Limited | Construction | 2007 |
| Mark II Holdings Limited | Financial services | 2018 |
| Marketsmart Limited | Wholesale & retail | 2001 |
| Marldon Marquees Limited | Administrative & support | 2009 |
| Marlow Mechanical Ltd | Construction | 2020 |
| Marlpark Electrical Limited | Construction | 2013 |
| Marmik Window Machinery Limited | Manufacturing | 2004 |
| Marsh Investments (North) Ltd | Manufacturing | 2003 |
| Marsha Miles Consultancy Limited | Administrative & support | 2017 |
| Marshall Plant Hire Limited | Agriculture & fishing | 2007 |
| Marshalls Electrical Contractors Limited | Construction | 2009 |
| Marsland Nash Associates Ltd | Professional & scientific | 2003 |
| Martin Buhagiar Properties Ltd | Real estate | 2026 |
| Martin-Cutts Consulting Ltd | Professional & scientific | 2022 |
| Martinez Consultancy Ltd | Professional & scientific | 2025 |
| Martyn Ward Limited | Professional & scientific | 2003 |
| Maskery Wealth Management Ltd | Financial services | 2016 |
| Maskery WM Ltd | Financial services | 2025 |
| Mason Developments Limited | Construction | 2011 |
| Mason Ecommerce Ltd | Wholesale & retail | 2024 |
| Master Class Education (South West) Limited | Administrative & support | 2013 |
| Match Strike Ltd | Professional & scientific | 2023 |
| Matrix Performance Ltd | Professional & scientific | 2020 |
| Matrix Productions Ltd | Information & communication | 2026 |
| Matt Bayles Professional Tree Care Ltd | Agriculture & fishing | 2007 |
| Matt Smith Plant Hire Limited | Administrative & support | 2016 |
| Matterealise Limited | Professional & scientific | 2014 |
| Matthew Masters Transport Solutions Ltd | Professional & scientific | 2021 |
| Mavbrick Ltd | Real estate | 2025 |
| Maven App Ltd | Information & communication | 2026 |
| Maven Creative Limited | Information & communication | 2021 |
| Maven Solutions Ltd | Professional & scientific | 2021 |
| Maxllg Ltd | Information & communication | 2019 |
| Maxwell Investments Limited | Real estate | 2021 |
| Maxwells Consultancy Limited | Extraterritorial | 2004 |
| MBB Transport Ltd | Transport & logistics | 2020 |
| MBP Fire Protection Ltd | Construction | 2019 |
| MC Hearing Services (SW) Limited | Health & social care | 2021 |
| Mc-Do-Well Homes Ltd | Real estate | 2025 |
| MCA Inc. Ltd | Wholesale & retail | 2023 |
| Mcblacklin Ltd | Real estate | 2017 |
| Mccarthy (Contractors) SW Limited | Construction | 2001 |
| Mcclennon Developments Limited | Construction | 2018 |
| Mcgrath Paving Ltd | Construction | 2022 |
| Mcpherson Jarvie Medical Limited | Health & social care | 2022 |
| Mcurson Ltd | Construction | 2020 |
| Mdlll Limited | Real estate | 2022 |
| MDP (Holdings) Limited | Financial services | 2014 |
| Meadow Estates (SW) Limited | Construction | 2018 |
| Meadows Construction Ltd | Construction | 2015 |
| MEAT59 (Exeter) Limited | Hospitality | 2016 |
| Meddings Thermalec Limited | Manufacturing | 1969 |
| Media Asset Capital Limited | Professional & scientific | 2002 |
| Mediquate Consultancy Limited | Professional & scientific | 2024 |
| Mediterranean Plant Company Ltd | Wholesale & retail | 2016 |
| Meetingbooker Ltd | Administrative & support | 2017 |
| Megan GEE Design Ltd | Professional & scientific | 2024 |
| Meldon Hall Management Company Limited | Households | 1974 |
| Mella Design Limited | Construction | 1999 |
| Memphis Holdings Ltd | Hospitality | 2021 |
| Menai Cleaning Services Limited | Administrative & support | 2017 |
| Mendocino Ltd | Agriculture & fishing | 2015 |
| Mental Health for ALL Ltd | Information & communication | 2021 |
| Menu Bespoke Ltd | Hospitality | 2023 |
| Meraki Hair by Karla Newbury Limited | Other services | 2025 |
| Meraki Healing Limited | Other services | 2020 |
| Mercury Vets Limited | Professional & scientific | 2019 |
| Merrifield Motor Works Limited | Wholesale & retail | 2017 |
| Merrymeet (Investment) Limited | Financial services | 2023 |
| Mesopotamia Food Ltd | Hospitality | 2025 |
| Meta Communications Ltd | Information & communication | 2022 |
| Metal Fabrication South West Ltd | Manufacturing | 2017 |
| Michaelangelo (Devon) Limited | Real estate | 2010 |
| Michelle Lyons Interiors Ltd | Professional & scientific | 2005 |
| Micom 3 Ltd | Construction | 2015 |
| Micro Update Limited | Information & communication | 1987 |
| Middle Rocombe Farm Management Company Limited | Real estate | 2018 |
| Middleton Exeter Orthopaedics Limited | Health & social care | 2023 |
| Midnight Blue Tattoo Ltd | Other services | 2018 |
| Midnight Mentor Ltd | Health & social care | 2022 |
| Mike Evans Photography Limited | Professional & scientific | 2003 |
| Mike Harding Ltd | Wholesale & retail | 2015 |
| Mike Hutton TV Ltd | Information & communication | 2019 |
| Mike Pooley Consulting Ltd | Professional & scientific | 2023 |