| Mills Court (Helston) RTM Company Limited | Households | 2025 |
| Mills Maritime Ltd | Professional & scientific | 2016 |
| Minhoco 78 Limited | Real estate | 2022 |
| Minster Treatment Works Limited | Real estate | 2002 |
| Minwarth Ltd | Professional & scientific | 2017 |
| Mirage Marine Limited | Administrative & support | 2026 |
| MJG Developments Limited | Construction | 2024 |
| MJG Properties Limited | Construction | 2006 |
| MJH Software Consultants Limited | Information & communication | 2007 |
| MK Big Sale Ltd | Wholesale & retail | 2016 |
| Moon Bay Limited | Hospitality | 2018 |
| Moonbay Cuisine Limited | Hospitality | 2025 |
| Moonbay Helston Limited | Hospitality | 2023 |
| Moonflower 10 Limited | Hospitality | 2019 |
| Moore's Floors Limited | Wholesale & retail | 2004 |
| Morgan Workplace Consultancy Ltd | Professional & scientific | 2009 |
| Morkanto Limited | Administrative & support | 2011 |
| Morvoren Limited | Real estate | 2021 |
| Moth and Mole Solutions Ltd | Wholesale & retail | 2023 |
| Mounts Bay Holidays Limited | Real estate | 2009 |
| Movefortytwo Ltd | Real estate | 2019 |
| MRW Plumbing Ltd | Construction | 2021 |
| MSB Group Mechanical & Electrical Ltd | Construction | 2020 |
| MSB Heating Solutions Limited | Construction | 2019 |
| MSC Property Investments Ltd | Real estate | 2019 |
| Mullion Cottages Limited | Extraterritorial | 2011 |
| Mullion Cove Harbour Group Ltd | Transport & logistics | 2024 |
| Mullion Garage Limited | Construction | 1947 |
| Mullion Golf Club Trading Ltd | Wholesale & retail | 2018 |
| Mullion Mechanics Limited | Wholesale & retail | 2014 |
| Mullion Village Community Interest Company | Administrative & support | 2013 |
| Music & Dance Education Limited | Education | 2003 |
| Music and Dance Education Trust | Arts & recreation | 1997 |
| Music Marketing Global Ltd | Wholesale & retail | 2023 |
| Mussel Shoal Brewery Ltd | Manufacturing | 2020 |
| Mussel Shoal Newquay Ltd | Hospitality | 2023 |
| Mussel Shoals Carlyon Ltd | Hospitality | 2023 |
| Mussel Shoals Ltd | Hospitality | 2018 |
| Mustard Seed (SW) | Other services | 2008 |
| MW Property Solutions Ltd | Construction | 2013 |
| MW Solar Limited | Construction | 2021 |
| My Drinks Club (UK) Ltd | Wholesale & retail | 2024 |
| Mycelium Studio Ltd | Professional & scientific | 2019 |
| N Moss & Co Limited | Hospitality | 2018 |
| N S Crisp Building & Roofing Limited | Construction | 2010 |
| Nalu Travel & Events Ltd | Administrative & support | 2023 |
| National Fishery Services Ltd | Agriculture & fishing | 2018 |
| Natterjack Properties Limited | Real estate | 2024 |
| Natural Pools Cornwall Ltd | Administrative & support | 2025 |
| Nature Connects CIC | Health & social care | 2020 |
| Nature Works Brands Limited | Manufacturing | 2010 |
| Nauti BUT Ice Limited | Hospitality | 2011 |
| Negys Ltd | Information & communication | 2011 |
| Neil Rowe Farming Limited | Agriculture & fishing | 2018 |
| Neville J Harris Insurance Brokers Ltd | Financial services | 2020 |
| New Habits Ltd | Health & social care | 2023 |
| New Harmony Fishing Ltd | Agriculture & fishing | 2024 |
| New Wave Pilates Ltd | Arts & recreation | 2023 |
| Newleaf Group Ltd | Real estate | 2022 |
| Newman Design Consultancy Limited | Professional & scientific | 2025 |
| Newton Holiday Cottages Ltd | Hospitality | 2022 |
| Nick Puttick Marine Services Limited | Professional & scientific | 2021 |
| Nick Street Electrical Ltd | Construction | 2019 |
| Nick Sturmy Limited | Construction | 2002 |
| Nicola Bealing Ltd | Arts & recreation | 2014 |
| Nigel Neil Sumpter Limited | Extraterritorial | 2025 |
| Nigel Thurley Automotive Limited | Wholesale & retail | 2003 |
| NJG Construction Ltd | Construction | 2025 |
| NKH Groundworks Ltd | Construction | 2025 |
| Nomad Seafoods Limited | Agriculture & fishing | 2025 |
| North Coast Services Limited | Construction | 2016 |
| NOW Kitchens Limited | Manufacturing | 2017 |
| NP Engineering Limited | Professional & scientific | 2015 |
| Nutrient Neutrality Solutions Limited | Professional & scientific | 2025 |
| NV Solar and Electrical Ltd | Construction | 2023 |
| Oak Ridge Natural Build Ltd | Construction | 2014 |
| Oaktide Construction Ltd | Construction | 2026 |
| Oasis Petroleum Exploration Consultants Limited | Mining & quarrying | 2000 |
| Oceangreens Ltd | Agriculture & fishing | 2025 |
| Old Corn Mill Gweek (Management) Limited | Administrative & support | 1979 |
| Olivers Estate Agents (Cornwall) Limited | Real estate | 2013 |
| OM & WC Limited | Real estate | 2026 |
| Optima Eventum Ltd | Administrative & support | 2012 |
| Orange Labs Ltd | Information & communication | 2026 |
| Orca Sea Safaris Ltd | Transport & logistics | 2010 |
| Orchard Court (Basingstoke) Management Company Limited | Households | 2005 |
| ORI Design Agent Ltd | Wholesale & retail | 2025 |
| Orion Conservation Services Limited | Administrative & support | 2022 |
| Oswald London Ltd | Professional & scientific | 2017 |
| OTC Building Limited | Construction | 2015 |
| OTC Developers Limited | Construction | 2019 |
| Oyster Holdings Limited | Professional & scientific | 2016 |
| P&B Lettings Limited | Real estate | 2025 |
| Paddle Steamer Ryde Trust | Extraterritorial | 2006 |
| Padstow Private Hire and Taxi Ltd | Transport & logistics | 2023 |
| Painless Fittings Limited | Construction | 2006 |
| Panama Music Limited | Information & communication | 1991 |
| Paradolia Ltd | Arts & recreation | 2023 |
| Parc Bottom Engine Works Limited | Professional & scientific | 2020 |
| Parker Diving Limited | Manufacturing | 1993 |