| Mannington Consulting Ltd | Professional & scientific | 2024 |
| Manor Commercial Business Services Ltd | Professional & scientific | 2019 |
| Manor Farms (Little Milton) Limited | Agriculture & fishing | 1993 |
| Manor Homes (Dorset) Ltd | Construction | 2002 |
| Mansouth Ltd. | Construction | 2005 |
| Manston and Sons Limited | Construction | 2014 |
| Mantage Limited | Professional & scientific | 2020 |
| Mantis BIO Ltd | Professional & scientific | 2025 |
| Maple Leaf Intelligence Limited | Information & communication | 2024 |
| Mapleview Ltd | Information & communication | 1997 |
| Maplow Ltd | Information & communication | 2024 |
| Marche Consulting Limited | Information & communication | 2023 |
| Marchmont Farms Limited | Agriculture & fishing | 1983 |
| Marden Edwards Group Holdings Limited | Financial services | 2011 |
| Marden Edwards Limited | Manufacturing | 1931 |
| Marden Edwards Property Limited | Real estate | 2018 |
| Margaret Turner Limited | Wholesale & retail | 1995 |
| Marina Garage Limited | Wholesale & retail | 1983 |
| Marine Resources Ltd | Professional & scientific | 2014 |
| Marine Services Poole LLP | | 2015 |
| Mark Bowles Plastering Limited | Construction | 2025 |
| Mark Brookfield Limited | Information & communication | 2011 |
| Mark Field Fitness Ltd | Other services | 2019 |
| Mark Hinsley Arboricultural Consultants Limited | Agriculture & fishing | 2010 |
| Mark RAE Music Ltd | Information & communication | 2001 |
| Market Court Hayle RTM Company Limited | Real estate | 2009 |
| Marketing Plus Agency Limited | Professional & scientific | 2024 |
| Markets Evolution Ltd | Professional & scientific | 2014 |
| Markets Made Simple Ltd | Information & communication | 2025 |
| Marks Yard (Wimborne) Management Limited | Households | 2018 |
| Marlborough Court Management Company Limited | Administrative & support | 1981 |
| Marlie Makes Ltd | Manufacturing | 2020 |
| Marlou Homes Limited | Real estate | 2024 |
| Marlow Consulting Ltd | Professional & scientific | 2024 |
| Marquee Print Limited | Manufacturing | 2022 |
| Marsden Consulting Limited | Professional & scientific | 2023 |
| Marshalls Consulting Ltd | Professional & scientific | 2025 |
| Mart MU Ltd | Real estate | 2025 |
| Marte Marie Forsberg Photography Ltd | Arts & recreation | 2015 |
| Martin Avenue Limited | Construction | 2024 |
| Martin Beardsley Limited | Construction | 2012 |
| Marvela Group Ltd | Professional & scientific | 2024 |
| Masala Boss Wimborne Ltd | Hospitality | 2025 |
| Maskell Properties Limited | Real estate | 2021 |
| Mason & Turner Ltd | Construction | 2005 |
| Matbo Solutions Limited | Information & communication | 2022 |
| Matex LAB UK Ltd | Wholesale & retail | 2020 |
| Mathew Wheatley Ltd | Professional & scientific | 2020 |
| Matisa Services Limited | Information & communication | 2014 |
| Matrix Quantity Surveying Services Limited | Professional & scientific | 2023 |
| Matrod Frampton Limited | Construction | 2000 |
| Matsis Solutions Ltd | Information & communication | 2024 |
| Matt Rigbye Consulting Ltd | Information & communication | 2024 |
| Matthew Barlow Psychology Services Ltd | Education | 2025 |
| Matthew CB Communications Limited | Professional & scientific | 2023 |
| Matthew Urquhart IT Consultant Limited | Information & communication | 2024 |
| Mauveworx Ltd | Manufacturing | 2017 |
| Maven Publishing Ltd | Information & communication | 2018 |
| Mavilly's Meadow Ltd | Health & social care | 2026 |
| Mavoks Design Ltd | Professional & scientific | 2023 |
| Mavrik Ltd | Professional & scientific | 2025 |
| Mavu Ltd | Professional & scientific | 2025 |
| Maw-Pm Limited | Information & communication | 2022 |
| Mawgan Limited | Extraterritorial | 2021 |
| Mawgan VFT Limited | Professional & scientific | 2017 |
| MAX Alpha Limited | Professional & scientific | 2017 |
| MAX Dyer Ltd | Professional & scientific | 2026 |
| Maxbelle Ltd | Wholesale & retail | 2017 |
| Maxim Olliver Consulting Limited | Professional & scientific | 2024 |
| Maximal Fire Ltd | Information & communication | 2024 |
| Maxspace Interiors Ltd | Professional & scientific | 2012 |
| Maxwell S Manston Ltd | Construction | 2020 |
| Maya Beauty Wimborne Limited | Other services | 2025 |
| Mayfly Vintage Limited | Wholesale & retail | 2019 |
| Mayteq Ltd | Information & communication | 2025 |
| Mazac IT Consultancy Limited | Information & communication | 2024 |
| Mazda Tech Limited | Information & communication | 2020 |
| MB Interior Contracting Limited | Construction | 2016 |
| Mbcb Holdings Limited | Professional & scientific | 2013 |
| Mbody Limited | Health & social care | 2025 |
| MBR Consulting Services Ltd | Information & communication | 2023 |
| MC Automotive Centre Ltd | Wholesale & retail | 2025 |
| MC Immersive Ltd | Other services | 2020 |
| MC IT Technical Solutions Limited | Information & communication | 2014 |
| MC Projects (Dorset) Ltd | Construction | 2022 |
| MC Shed Limited | Real estate | 2021 |
| Mcarrow Engineering Ltd | Information & communication | 2022 |
| Mcdonnell Medical Communications Ltd | Professional & scientific | 2022 |
| Mcgrath Healthcare Ltd | Health & social care | 2022 |
| MCH Limited | Construction | 2005 |
| Mckie Farming Ltd | Agriculture & fishing | 2025 |
| Mckie Taylor-Brown Ltd | Professional & scientific | 2023 |
| Mcmorton Developments Limited | Real estate | 2017 |
| Mcms Property Group Ltd | Real estate | 2023 |
| Mcnidder & Grace Limited | Information & communication | 2011 |
| Mcol Developments Ltd | Construction | 2022 |
| MCP Holdings (U.K) Limited | Financial services | 2017 |
| MCP Projects (U.K) Limited | Real estate | 2017 |
| MCP Properties (U.K) Ltd | Real estate | 2006 |
| Mcyc Studio Ltd | Professional & scientific | 2023 |