| Mike Coad Ltd | Wholesale & retail | 2021 |
| Mike Martin Window Systems Limited | Construction | 2018 |
| MIL Collections Ltd | Administrative & support | 2003 |
| MIL Outsource Limited | Administrative & support | 2010 |
| Milk IT Bakehouse Limited | Manufacturing | 2025 |
| Millands Home Ltd | Professional & scientific | 2024 |
| Miller and SON SW LLP | | 2012 |
| Miller Commercial LLP | | 2012 |
| Millers Gardening & General Maintenance Ltd | Administrative & support | 2026 |
| Millerson (Camborne) Limited | Real estate | 2025 |
| Millerson (Hayle) Limited | Real estate | 2025 |
| Millgate Hospitality Limited | Hospitality | 2025 |
| Millmerran Limited | Manufacturing | 2026 |
| Mind Feast Games Ltd | Information & communication | 2020 |
| Mine Smart Solutions Ltd | Information & communication | 2023 |
| Miners Court Flats Ltd | Households | 2005 |
| Miners Limited | Real estate | 1949 |
| Mining Education Training and Learning Limited | Professional & scientific | 2020 |
| Mint Construction South West Ltd | Construction | 2026 |
| Mint House Interiors Limited | Professional & scientific | 2014 |
| Mintmech Engineering Services Ltd | Professional & scientific | 2026 |
| Mintmech Holding Ltd | Financial services | 2026 |
| Mintmech Limited | Professional & scientific | 2018 |
| Minx Entertainment Limited | Arts & recreation | 2014 |
| Mirchi (Bude) Ltd | Hospitality | 2015 |
| Mirect Goods Ltd | Wholesale & retail | 2025 |
| Mirror Image Yachts Ltd | Manufacturing | 2007 |
| Mitchell and Andrew Limited | Construction | 2015 |
| Mixcourt Limited | Administrative & support | 2007 |
| MJA Property Development and Investors Limited | Administrative & support | 2017 |
| MJC Appliance Care Ltd | Manufacturing | 2013 |
| MJC Consulting (SW) Limited | Construction | 2019 |
| Mjjs Building Services Ltd | Construction | 2018 |
| MK 1 Cortina Owners Club Limited | Other services | 2011 |
| MK2AV LLP | | 2013 |
| ML Engineering Design Limited | Professional & scientific | 2014 |
| ML Plumbing & Heating Ltd | Construction | 2024 |
| MM Photography & Video Ltd | Professional & scientific | 2022 |
| MM Travel & Digital Ltd | Professional & scientific | 2025 |
| MMB Respiratory Limited | Health & social care | 2021 |
| MMW Property Developments Limited | Construction | 2022 |
| MNS Construction Ltd | Construction | 2016 |
| Mobility Adaptations Limited | Other services | 2013 |
| Modelplain Limited | Real estate | 2001 |
| Modular Mapper Limited | Information & communication | 2017 |
| Modus Operandi Consultants Ltd | Professional & scientific | 2015 |
| Mojo Climbing Limited | Manufacturing | 2006 |
| Molendotech Limited | Administrative & support | 2017 |
| Molwin Estates Limited | Construction | 1994 |
| Molwin Investments Limited | Real estate | 2014 |
| Monalisa Production Ltd | Wholesale & retail | 2025 |
| Monkey Puzzle Art Ltd | Manufacturing | 2020 |
| Monks Way Residents Association Ltd | Households | 2024 |
| Monster Minders Ltd | Health & social care | 2021 |
| Monster Mowing Cornwall Ltd | Administrative & support | 2025 |
| Moon Phase Studio Ltd | Wholesale & retail | 2020 |
| Moonfleet Investments Ltd | Real estate | 2024 |
| MOR and Wild Ltd | Arts & recreation | 2026 |
| MOR Cornwall Limited | Hospitality | 2024 |
| MOR Finance Limited | Financial services | 2025 |
| MOR Interiors Limited | Wholesale & retail | 2017 |
| MOR Outdoors Ltd | Other services | 2025 |
| MOR-2-EAT Limited | Hospitality | 2016 |
| Moresk Holdings Limited | Financial services | 2023 |
| Morgan Masonry Limited | Manufacturing | 1988 |
| Morganic Healing Ltd | Wholesale & retail | 2014 |
| Morlaix Ltd | Financial services | 2010 |
| Morrow Partners Limited | Extraterritorial | 2007 |
| Morse's Wood Ltd | Real estate | 2014 |
| Morton's Golfpro Services Limited | Wholesale & retail | 2013 |
| Morva Carpentry & Construction Ltd | Construction | 2024 |
| Morva Construction Ltd | Construction | 2026 |
| Moses Site Engineering Limited | Construction | 2017 |
| Mosevic Collection Limited | Manufacturing | 2017 |
| Motor Dance Journal Ltd | Information & communication | 2022 |
| Mount Pleasant Farm Developments (2026) Limited | Construction | 2026 |
| Mount Pleasant Farm Investments (2026) Limited | Real estate | 2026 |
| Mounts Bay Beach Huts Ltd | Real estate | 2024 |
| Mowhay Manna Limited | Energy | 2012 |
| MR Falmouth Land Train Tours Limited | Real estate | 2025 |
| MR Scorse Ltd | Administrative & support | 2017 |
| Ms&D Ltd | Construction | 2013 |
| MSK Aware CIC | Health & social care | 2020 |
| MSS Hospitality Limited | Hospitality | 2023 |
| MTA Stores Ltd | Wholesale & retail | 2024 |
| MTT Developments Limited | Construction | 2017 |
| Mundo Holdings Limited | Financial services | 2026 |
| Mundo SPV1 Limited | Financial services | 2026 |
| Murrell Associates LLP | | 2018 |
| Murugesan Urology Services Limited | Health & social care | 2019 |
| Music Halls Project Ltd | Arts & recreation | 2017 |
| MWG Estates Limited | Real estate | 2004 |
| Mwjv Ltd | Professional & scientific | 2018 |
| MWR Media Limited | Administrative & support | 2002 |
| MWS Property Services Limited | Real estate | 2022 |
| My BRU Ltd | Hospitality | 2025 |
| My Coast Limited | Information & communication | 2020 |
| My Cornwall Limited | Information & communication | 2023 |
| My Divorce Club Ltd | Other services | 2025 |
| My Dog Wash Limited | Administrative & support | 2024 |