| Mike Ruth Plumbing & Heating Limited | Construction | 2011 |
| Mike's Maths Limited | Education | 2015 |
| Milber Construction and Management Services Limited | Construction | 2012 |
| Milber Court Management Company Limited | Households | 2015 |
| Milber Developments Limited | Real estate | 2014 |
| Milber Estates Limited | Real estate | 1995 |
| Milber Salvage & Spares Limited | Water & waste | 2003 |
| Miles Coatings Limited | Manufacturing | 2019 |
| Milestones Veterinary Centre Limited | Professional & scientific | 2011 |
| Mill END Hotel (UK) Limited | Hospitality | 1998 |
| Mill Management Company (N a) Limited | Households | 2005 |
| Millbrook Villas Limited | Health & social care | 2013 |
| Milldc Limited | Professional & scientific | 2015 |
| Millen Drywall Limited | Construction | 2011 |
| Miller Bay Limited | Construction | 2013 |
| Miller-Reid Consultancy Ltd | Education | 2024 |
| Mills Medical Consultancy Services Limited | Health & social care | 2015 |
| Millside Therapy Ltd | Health & social care | 2021 |
| Miltons of Salcombe Ltd | Wholesale & retail | 2007 |
| Miltonside Limited | Real estate | 2014 |
| Mind That Large GAP Limited | Arts & recreation | 2016 |
| Minds Align Limited | Administrative & support | 2022 |
| Mindwise Management Limited | Professional & scientific | 2025 |
| Minerva Accounting Solutions Ltd | Professional & scientific | 2009 |
| Mintaka Coffee Limited | Hospitality | 2022 |
| Mintbrook Properties Limited | Real estate | 2002 |
| Mirage (Ipplepen) Limited | Hospitality | 2013 |
| Mista Trading Ltd | Wholesale & retail | 2025 |
| Mital&Sons Ltd | Wholesale & retail | 2022 |
| Mitus Transportation Limited | Transport & logistics | 2021 |
| Mixin Consultancy Ltd | Information & communication | 2022 |
| Mixin Homecare Ltd | Health & social care | 2023 |
| Mizen (Consultation & Training) Ltd | Health & social care | 2024 |
| Mj&Tjw Property Management Ltd | Real estate | 2025 |
| Mjdrains Ltd | Administrative & support | 2017 |
| MJE Accounting Limited | Professional & scientific | 2012 |
| MJE Electrical Services SW Ltd | Construction | 2018 |
| MJS Scaffolding Ltd | Construction | 2016 |
| MJT Services Limited | Information & communication | 2015 |
| MJW Red Barn Ltd | Construction | 2025 |
| MK Envirocare Services Limited | Administrative & support | 2003 |
| MK Fire & Security Ltd | Public administration | 2022 |
| MKH Architects Ltd | Professional & scientific | 2024 |
| MLB Aesthetics & Beauty Ltd | Other services | 2024 |
| MLB Hospitality Ltd | Hospitality | 2024 |
| MLR Ltd | Financial services | 2020 |
| MLS Roofing Ltd | Construction | 2022 |
| MLS Scaffolding Ltd | Construction | 2026 |
| MLS Waste Ltd | Water & waste | 2024 |
| MM 24 HR Auto Services Limited | Wholesale & retail | 2019 |
| MMC Property Holdings Limited | Real estate | 2017 |
| MN Enamel Limited | Health & social care | 2025 |
| Mo'Wax Music Limited | Information & communication | 1995 |
| Mobile Arena Bristol Limited | Wholesale & retail | 2019 |
| Modemma Ltd | Hospitality | 2024 |
| Modu Hygiene Limited | Extraterritorial | 2026 |
| Momentum Clinic Newton Abbot Ltd | Health & social care | 2021 |
| MON Freq Limited | Information & communication | 2025 |
| Mondeor Group Ltd | Financial services | 2025 |
| Monepi Ltd | Real estate | 2024 |
| Monmouth Ltd | Real estate | 1957 |
| Monopoli Capital Limited | Professional & scientific | 2021 |
| Monopoli Consulting Ltd | Administrative & support | 2023 |
| Monotch UK Limited | Information & communication | 2025 |
| Monstarz Holdings Ltd | Financial services | 2025 |
| Monte Rosa Management Company Limited | Households | 1980 |
| Monterey Park (Management Company) Limited | Other services | 2008 |
| Montis Energy Group Ltd | Construction | 2023 |
| Montpellier House Limited | Real estate | 2002 |
| Monument Fuels Limited | Wholesale & retail | 2011 |
| Mooch Art and Makers Ltd | Wholesale & retail | 2026 |
| Moonhoney Meadery Ltd | Manufacturing | 2020 |
| Moonstone Hotel Limited | Hospitality | 2022 |
| Moor & Shore Estates Ltd | Real estate | 2025 |
| Moor Amps Ltd | Manufacturing | 2018 |
| Moor Barton Wilding CIC | Agriculture & fishing | 2022 |
| Moor Cleaning Services Ltd | Administrative & support | 2024 |
| Moor Medical Limited | Health & social care | 2019 |
| Moor Park Residents Limited | Households | 1989 |
| Moor-Build Ltd | Construction | 2020 |
| MOOR2SEA Outdoors Ltd | Arts & recreation | 2025 |
| Moorcrest Investments Limited | Administrative & support | 2025 |
| Moores Construction (SW) Ltd | Construction | 2017 |
| Moores Developments (SW) Ltd | Construction | 2020 |
| Moores Maintenance (SW) Limited | Households | 2022 |
| Moorland Blast Cleaning Limited | Administrative & support | 2010 |
| Moorland Bookkeeping Ltd | Professional & scientific | 2025 |
| Moorland Guides Limited | Arts & recreation | 2011 |
| Moorland Property Development Ltd | Administrative & support | 2014 |
| Moorland View South West Limited | Financial services | 2021 |
| Moorswood Ltd | Manufacturing | 2017 |
| Morden Solutions (UK) Limited | Administrative & support | 2007 |
| Moreton Newsagents Ltd | Wholesale & retail | 2020 |
| Moretonhampstead Development Trust | Other services | 2004 |
| Moretonhampstead Information Centre Ltd | Administrative & support | 2003 |
| Moretonhampstead Sports and Community Centre Limited | Arts & recreation | 2009 |
| Morgan Hacking Limited | Wholesale & retail | 2009 |
| Morgan Properties Limited | Real estate | 1982 |
| Morrell Electrical Limited | Construction | 2014 |
| Morris Aesthetics Limited | Health & social care | 2013 |