| Martin Horwell Ltd | Construction | 2022 |
| Martin Miller Financial Services Limited | Financial services | 2012 |
| Martin Parker Limited | Information & communication | 2014 |
| Martins Landscaping Limited | Administrative & support | 2012 |
| Martyn Bounsall Plumbing and Heating Ltd | Construction | 2023 |
| Marvell House (Plymouth) RTM Company Limited | Households | 2024 |
| Masala Street Ltd | Hospitality | 2026 |
| Mascott Holdings Limited | Construction | 2017 |
| Mash Care Services Ltd | Health & social care | 2015 |
| Mason & Page Bakehouse Ltd | Manufacturing | 2026 |
| Massdesigned Ltd | Professional & scientific | 2023 |
| Massdeveloped Ltd | Professional & scientific | 2022 |
| Master Cutz Ltd | Other services | 2026 |
| Masy Chips Limited | Hospitality | 2025 |
| MAT Medicals Limited | Health & social care | 2012 |
| Match Local Ltd | Information & communication | 2026 |
| Matechpower UK Ltd | Manufacturing | 2014 |
| Matham Investments Limited | Financial services | 1992 |
| Mathematic UK Ltd | Information & communication | 2025 |
| Mather Construction Ltd | Construction | 2022 |
| Matheson Estates Limited | Real estate | 2014 |
| Matheson Financial Limited | Financial services | 2022 |
| Matheson Investments Ltd | Real estate | 2019 |
| Matheson Property Services Ltd | Real estate | 2006 |
| Matlock Court (Torquay) Limited | Households | 1986 |
| Matrix 17 Consulting Ltd | Professional & scientific | 2023 |
| Matrix Carpentry Services Ltd | Manufacturing | 2025 |
| Matrix Er/Hr Limited | Administrative & support | 2006 |
| Matrix Marketing & Media Solutions Ltd. | Professional & scientific | 2002 |
| Matt Rogers Farming Limited | Agriculture & fishing | 2020 |
| Matt Scott Limited | Arts & recreation | 2017 |
| Matter Matter Ltd | Professional & scientific | 2012 |
| Mattgee Limited | Professional & scientific | 2017 |
| Matthew Auburn Ltd | Information & communication | 2020 |
| Matthew Edward (Holdings) Limited | Professional & scientific | 2021 |
| Matthew Edward Developments Limited | Construction | 2021 |
| Matthew Edward Limited | Professional & scientific | 2020 |
| Matthew Kitchen Bodywork Ltd | Manufacturing | 2026 |
| Matthew Stevens & SON Limited | Manufacturing | 2004 |
| Matthew Stevens and SON Holdings Limited | Manufacturing | 2011 |
| Matthew Taylor Ltd | Education | 2024 |
| Matthews Sonography Ltd | Health & social care | 2026 |
| Mattmore Properties Ltd | Real estate | 2023 |
| Mattock Lane (Walpole) Management Company Limited | Households | 2011 |
| Maugre Limited | Wholesale & retail | 2024 |
| Maurice Parker Structural Engineers Limited | Professional & scientific | 2009 |
| MAV FSA Limited | Public administration | 2026 |
| Maven Kairos Associates Ltd | Information & communication | 2025 |
| Maverick Consultancies Ltd | Professional & scientific | 2017 |
| Maverick Roofing Solutions Limited | Construction | 2023 |
| Maverickjack Ltd | Administrative & support | 2024 |
| Maverrik Digital Services Ltd | Professional & scientific | 2020 |
| Maverrik Ventures Limited | Financial services | 2014 |
| Mavic Services Limited | Extraterritorial | 2013 |
| Mavx Ltd | Professional & scientific | 2022 |
| Mavy T Media Ltd | Information & communication | 2025 |
| MAX and Scarlett Limited | Real estate | 2021 |
| Maxim-Eyes Opticians Limited | Wholesale & retail | 2013 |
| Maximise Construction Ltd | Construction | 2018 |
| Maximum Hire Ltd | Administrative & support | 2021 |
| Maximus Profitus Ltd | Construction | 2026 |
| Maxwon Ltd | Construction | 2019 |
| MAY Asset Management Ltd | Real estate | 2019 |
| MAY Fong Kitchen Limited | Hospitality | 2021 |
| MAY Groundworks Ltd | Construction | 2026 |
| MAY Group (SW) Ltd | Financial services | 2019 |
| MAY Recruitment Specialists Ltd | Administrative & support | 2020 |
| MAY Skye Services Ltd | Construction | 2019 |
| Mayajoy Design Ltd | Wholesale & retail | 2025 |
| Mayer Developments (SW) Limited | Construction | 2022 |
| Mayer Estate Agents Ltd | Other services | 2015 |
| Mayer Properties (SW) Ltd | Real estate | 2021 |
| Mayfair House RTM Company Limited | Households | 2020 |
| Mayfair Properties Plymouth Limited | Real estate | 2022 |
| Mayfair Restaurant (Seaton Carew) Ltd | Hospitality | 2019 |
| Mayflower Bidco Limited | Financial services | 2023 |
| Mayflower College of English Limited | Education | 1988 |
| Mayflower Connections Ltd | Wholesale & retail | 2024 |
| Mayflower Developments Limited | Construction | 2025 |
| Mayflower Evaluations Ltd | Manufacturing | 2020 |
| Mayflower Finco Limited | Financial services | 2023 |
| Mayflower House Art Limited | Wholesale & retail | 2011 |
| Mayflower House Limited | Health & social care | 2008 |
| Mayflower Medical Supplies Limited | Administrative & support | 2007 |
| Mayflower Moves Ltd | Real estate | 2025 |
| Mayflower Travel Limited | Transport & logistics | 2013 |
| Mayflowerstone Limited | Construction | 2006 |
| Mayford Financial Services Limited | Professional & scientific | 2009 |
| Mayorlyte Ltd | Transport & logistics | 2024 |
| Mayprath Property Ltd. | Real estate | 2013 |
| Maytec Solutions Ltd | Manufacturing | 2010 |
| MAZ K Properties Ltd | Real estate | 2022 |
| Mazingtree Limited | Information & communication | 2006 |
| MB Air-Conditioning & Mechanical Engineering Services Ltd | Energy | 2018 |
| MB Environmental SW Ltd | Administrative & support | 2026 |
| MB Motor Services Limited | Wholesale & retail | 2019 |
| MB Partnership Ltd | Wholesale & retail | 2026 |
| MB Psych Limited | Health & social care | 2020 |
| MB Suites Ltd | Real estate | 2025 |
| MBF Partners Limited | Transport & logistics | 2026 |