| MAP Lettings Agents Limited | Real estate | 2025 |
| Marine Connect Network Limited | Information & communication | 2026 |
| Maritime ASW & Rescue Ltd | Professional & scientific | 2026 |
| Mark Bryant Construction Limited | Construction | 1995 |
| Mark D Knuckey Ltd | Real estate | 2006 |
| Mark Perry Developments Limited | Construction | 2010 |
| Market JEW Street (Penzance) Management Company Limited | Households | 2019 |
| Martyn Rowe Auctioneers and Valuers Ltd | Wholesale & retail | 2012 |
| Matronius Limited | Information & communication | 2025 |
| Mawgan Porth Land Ltd | Real estate | 2026 |
| Mawla Trading Limited | Water & waste | 2017 |
| Maxfair Ltd | Hospitality | 2012 |
| Mayjan Limited | Wholesale & retail | 2021 |
| Mayne's Garage,Limited | Construction | 1929 |
| Mcfarland Property Limited | Manufacturing | 2025 |
| Mcfb Builders Ltd | Construction | 2024 |
| Mcgrane S.E.S Ltd | Construction | 2014 |
| Mcnicol-Jones Property Limited | Real estate | 2018 |
| Meat Machine Cornwall Ltd | Wholesale & retail | 2023 |
| Meatsupermarket.Com Limited | Wholesale & retail | 2017 |
| Megarry Ltd | Professional & scientific | 1994 |
| Meltec Ltd | Construction | 2023 |
| Melvill Court (Management Company) Limited | Households | 2001 |
| Merc Autocare Ltd | Wholesale & retail | 2016 |
| Merlin Cinemas Limited | Arts & recreation | 1998 |
| Mermaid Films Limited | Information & communication | 1999 |
| Mesen Property Ltd | Real estate | 2023 |
| MFH Enterprises Limited | Wholesale & retail | 2019 |
| MG Business Ltd | Transport & logistics | 2026 |
| MGB (Cornwall) Investment 1 Limited | Financial services | 2026 |
| MGB (Cornwall) Limited | Financial services | 2023 |
| Micro Living Ltd | Construction | 2016 |
| Mike Bennett Limited | Professional & scientific | 1963 |
| Miko Coffee Limited | Wholesale & retail | 1982 |
| Miko Coffee South West Ltd | Wholesale & retail | 1993 |
| Milkflo Dairy Systems Limited | Agriculture & fishing | 2006 |
| Milkwood Publishing Limited | Wholesale & retail | 2000 |
| Millennium Classics & Restorations Limited | Extraterritorial | 2003 |
| Millennium Classics Limited | Extraterritorial | 2003 |
| Millennium Mechanics Ltd | Wholesale & retail | 2026 |
| Millennium Motorsport (UK) Limited | Wholesale & retail | 1998 |
| Millennium Plants (Cornwall) Ltd | Wholesale & retail | 2003 |
| Mindbody Gynae Limited | Health & social care | 2025 |
| Mindquest Limited | Education | 2022 |
| Miners Arms (SW) Ltd | Hospitality | 2018 |
| Mini Machines Cornwall Ltd | Construction | 2026 |
| Mining Exchange Studios CIC | Wholesale & retail | 2021 |
| Mining EYE Ltd | Financial services | 2013 |
| Mitchell & Webber (Enterprises) Limited | Professional & scientific | 1981 |
| Mitchell & Webber Limited | Wholesale & retail | 1966 |
| Mitchell Concrete Ltd | Manufacturing | 2018 |
| Mitchell Court Residents Association Limited | Real estate | 2003 |
| MIX4YOU Concrete Limited | Manufacturing | 2016 |
| MJL Ashill Limited | Construction | 2020 |
| MJL Contractors Limited | Construction | 2006 |
| MJL Developments (Cornwall) Limited | Construction | 2011 |
| MJL Holdings SW Limited | Construction | 2001 |
| MJL Homes SW Limited | Construction | 2025 |
| MJL Plant Hire (Cornwall) Limited | Construction | 2008 |
| MJL Winslade Limited | Construction | 2024 |
| MMG (Cornwall) Ltd | Wholesale & retail | 2025 |
| Mmsb Mgmt Limited | Households | 2019 |
| Moon Loom Craft Ltd | Wholesale & retail | 2026 |
| Moonchild and the Pirate Limited | Health & social care | 2024 |
| Moontide Swimwear Limited | Manufacturing | 2001 |
| Moor to Sea Services (SW) Limited | Other services | 2014 |
| Mordros Holdings Limited | Real estate | 2022 |
| Morlaix Network Solutions Limited | Information & communication | 2000 |
| Morlanow Management Company Limited | Real estate | 2016 |
| Morrab Road Property Management Co Limited | Households | 2011 |
| Morrish Properties Ltd | Real estate | 2017 |
| Morva Recruitment Limited | Administrative & support | 2023 |
| Mouldstop Limited | Wholesale & retail | 2018 |
| MPH Minerals Consultancy Ltd | Professional & scientific | 2015 |
| MR David P C Ltd | Agriculture & fishing | 2025 |
| MT3 Cycles Ltd | Wholesale & retail | 2019 |
| MT3 SW Ltd | Wholesale & retail | 2026 |
| MTN Electrical Ltd | Construction | 2023 |
| Multibeam Services Ltd | Professional & scientific | 2025 |
| Music for Good Ltd | Education | 2004 |
| Myathkar Ltd | Hospitality | 2025 |
| N T Enterprises (SW) Ltd | Real estate | 2019 |
| Nancekuke Lettings Limited | Real estate | 2020 |
| Natural Patterns Ltd | Arts & recreation | 2020 |
| Natural Spark Ltd | Construction | 2012 |
| Nautilus Owners Limited | Households | 2003 |
| Ndyl Ltd | Information & communication | 2025 |
| Neill Gorton Prosthetics Studio Limited | Arts & recreation | 2003 |
| Neill Sandys Ltd | Professional & scientific | 2023 |
| Netherwood Insight Ltd | Professional & scientific | 2025 |
| Neurofriendly Ltd | Professional & scientific | 2025 |
| New Green Ventures Limited | Administrative & support | 1997 |
| Newbias Solutions CIC | Information & communication | 2022 |
| Newseal Limited | Construction | 2004 |
| Nexgen Infrastructure Limited | Professional & scientific | 2022 |
| Next Wave Marketing Ltd | Professional & scientific | 2025 |
| Nice and Clear Ltd. | Health & social care | 2013 |
| Niche Property Maintenance Ltd | Construction | 2016 |
| Nick the Estate Agent Ltd | Real estate | 2025 |
| Niles Bakery Holdings Limited | Financial services | 2026 |