| Meci Suliana Limited | Wholesale & retail | 2023 |
| Medforth CS Ltd | Professional & scientific | 2024 |
| Medical Diagnostic Solutions Ltd | Professional & scientific | 2024 |
| Medineeds UK Ltd | Health & social care | 2020 |
| Medley Court (Exeter) Management NO 1 Limited | Households | 2004 |
| Medusa Media Consultancy Limited | Professional & scientific | 2025 |
| Medusa's Hair Salons Ltd | Other services | 2013 |
| Meet Cutes South West Ltd | Arts & recreation | 2025 |
| Mei's YOU Someset Limited | Hospitality | 2017 |
| Meijers Canatan Advocaten LLP | | 2020 |
| Meldon Consulting Limited | Administrative & support | 2002 |
| Melrose HR Ltd | Administrative & support | 2006 |
| Meltor Developments Limited | Real estate | 2010 |
| Meltor Properties Limited | Construction | 2012 |
| Meltor Somerset Limited | Construction | 2021 |
| Membership Plans Limited | Administrative & support | 2007 |
| Memoire Collective Ltd | Information & communication | 2026 |
| Memtec Holdings Ltd | Real estate | 2024 |
| Mendez Limited | Wholesale & retail | 2021 |
| Mendip Estates Limited | Real estate | 2003 |
| Mendip Ropemakers Limited | Manufacturing | 2012 |
| Mendip Stoves Limited | Extraterritorial | 2011 |
| Mendip Timber Designs Limited | Professional & scientific | 2016 |
| Meningitis Action Ltd | Health & social care | 2024 |
| Mercedes Bits Ltd | Wholesale & retail | 2025 |
| Mercury Business Park Management Company Limited | Households | 2020 |
| Mergate CIC | Arts & recreation | 2017 |
| Merlin Customs Ltd | Professional & scientific | 2024 |
| Merry Medical Ltd | Health & social care | 2018 |
| Merrythorn Limited | Real estate | 2018 |
| Message Masters Limited | Extraterritorial | 2004 |
| Metadosis Limited | Real estate | 2025 |
| Metal Contract Management Limited | Wholesale & retail | 1998 |
| Metal Monkey Designs Limited | Manufacturing | 2016 |
| Metis Creative Limited | Professional & scientific | 2021 |
| Metric Roofing Systems Ltd | Construction | 1994 |
| Metro Centre Ltd | Health & social care | 1992 |
| Metropole Court 2000 Limited | Real estate | 2001 |
| Mevagissey Bay View LLP | | 2011 |
| Mewp Operators Ltd | Construction | 2017 |
| Mews Commercial Limited | Real estate | 2017 |
| Meyar Ltd | Information & communication | 2021 |
| Mezzabarba UK Limited | Wholesale & retail | 2022 |
| Mg-Logos Ltd | Wholesale & retail | 2021 |
| Mgrr Ltd | Real estate | 2016 |
| MH Group Consulting Limited | Health & social care | 2015 |
| MH Technology Ltd | Information & communication | 2018 |
| MH Zackeriya Limited | Real estate | 2025 |
| MHH Davis Enterprises Limited | Wholesale & retail | 2016 |
| Mhpg 2020 Limited | Hospitality | 2020 |
| MI Specialty Ltd | Financial services | 2010 |
| MI Vets Ltd | Financial services | 2023 |
| Mi&Ma UK Limited | Wholesale & retail | 2026 |
| Micash Enterprise Ltd | Construction | 2009 |
| Michael Adams Landscaping Limited | Agriculture & fishing | 2007 |
| Michael Taxis Taunton Ltd | Transport & logistics | 2025 |
| Mickie Sharp Limited | Information & communication | 2011 |
| MID Somerset Forestry Limited | Agriculture & fishing | 2014 |
| MID Strategic Consulting Limited | Professional & scientific | 2024 |
| Middle Lodge Limited | Real estate | 2024 |
| Middle Street Holdings Ltd. | Real estate | 2010 |
| Middletons Motor Care Limited | Wholesale & retail | 2014 |
| Mielie Limited | Health & social care | 2007 |
| Mihai Iacob Ltd | Health & social care | 2012 |
| Mihai-Silviu Gherman Limited | Professional & scientific | 2016 |
| Mihaz Ltd | Professional & scientific | 2019 |
| Mijenin Limited | Financial services | 2019 |
| Mikare Ltd | Health & social care | 2017 |
| Mikclimax Concept Limited | Health & social care | 2023 |
| Mike and Charlie Ltd | Professional & scientific | 2021 |
| Mike Lock Construction Limited | Construction | 1989 |
| Mike Rogers Wealth Management (IFA) Limited | Financial services | 2011 |
| Mike's Classic Car Repairs Limited | Wholesale & retail | 2026 |
| Mikontact Ltd | Health & social care | 2025 |
| MIL10 Holdings | Financial services | 2021 |
| MIL10 Investments | Financial services | 2021 |
| Milan 1950 Limited | Administrative & support | 2025 |
| Milborne Place (Milborne) Management Company Limited | Households | 2015 |
| Miles Alexander Limited | Real estate | 2016 |
| Miles Tool & Machinery Centre Limited | Wholesale & retail | 1984 |
| Milford Court Management Company Limited | Households | 1987 |
| Mili Healthcare Limited | Wholesale & retail | 2001 |
| Mill House SW Ltd | Hospitality | 2022 |
| Mill Lane Properties Ltd | Extraterritorial | 2018 |
| Millichamp & Hall Limited | Manufacturing | 2010 |
| Million Trading Limited | Wholesale & retail | 2015 |
| Milliphore Ltd | Health & social care | 2023 |
| Mills PIC Holdings Ltd | Professional & scientific | 2024 |
| Mills Services Group Ltd | Financial services | 2020 |
| Millstones Limited | Wholesale & retail | 2003 |
| Millthorn House (Street) Management Company Limited | Real estate | 1992 |
| Milnor Property Ltd | Real estate | 2021 |
| Milsted Langdon Financial Services Limited | Financial services | 2000 |
| Milsted Langdon LLP | | 2007 |
| Milton Brothers Limited | Construction | 2013 |
| Milton Enterprises Limited | Agriculture & fishing | 2003 |
| Milton Lodge RTM Company Limited | Extraterritorial | 2011 |
| Milverton Enterprises Ltd | Real estate | 2025 |
| Milverton Studio Ltd | Professional & scientific | 2022 |
| Mime Architects Limited | Professional & scientific | 2010 |