| Meter Boxes UK Ltd | Manufacturing | 2019 |
| Metric Engineering Management Limited | Manufacturing | 2016 |
| Metric Real Estate Limited | Other services | 2019 |
| Metric UK Hire Ltd | Administrative & support | 2024 |
| Metro-Ducting Limited | Construction | 2013 |
| Mets Ltd | Construction | 2008 |
| MEW Meadow Solutions Ltd | Professional & scientific | 2021 |
| Mewstone Assets Limited | Real estate | 2014 |
| Mewstone Developments Limited | Construction | 2025 |
| Mewstone Events Ltd | Other services | 2025 |
| Mewstone Games Limited | Manufacturing | 2022 |
| Mewstone Physiotherapy Ltd | Other services | 2023 |
| Mewstone Wills and Estate Planning Ltd | Professional & scientific | 2024 |
| Mexicano Ltd | Hospitality | 2024 |
| Meze Grill Takeaway Ltd | Hospitality | 2024 |
| MFI Property LLP | | 2024 |
| Mfpb Ltd | Real estate | 2024 |
| MFS Properties Limited | Real estate | 2015 |
| Mfvuk Ltd | Manufacturing | 2019 |
| MFW Development Holdings Limited | Construction | 2024 |
| MG Bartlett Yacht Consulting Ltd | Manufacturing | 2024 |
| MG Coaching Limited | Arts & recreation | 2024 |
| MG Management Consultancy Ltd | Professional & scientific | 2019 |
| MGH Holdings Ltd | Financial services | 2018 |
| MGP Holdings Ltd | Real estate | 2015 |
| MGT Accounting Services Ltd | Professional & scientific | 2019 |
| MGT Seafoods Ltd | Wholesale & retail | 2025 |
| MH Associates Ltd | Other services | 2015 |
| MHJ Homes Ltd | Real estate | 2023 |
| MHL Consultants Ltd | Professional & scientific | 2017 |
| MHL H&S Ltd | Professional & scientific | 2025 |
| Mhmc Developments Limited | Construction | 2026 |
| MI Risk Associates Ltd | Professional & scientific | 2016 |
| Mia's Brews & Bubbles Ltd | Hospitality | 2026 |
| Miacorkish Ltd | Wholesale & retail | 2025 |
| Michael Inkpen F.G.A. Limited | Other services | 2003 |
| Michael Oliver 1975 Limited | Manufacturing | 2019 |
| Michael Pitts Limited | Information & communication | 2003 |
| Michael Sendall Transport Planning Liaison Limited | Professional & scientific | 2011 |
| Michael Spiers (Jewellers) Limited | Wholesale & retail | 1961 |
| Michael Wray Enterprises Limited | Manufacturing | 2018 |
| Michaela Livingstone Consulting Limited | Professional & scientific | 2026 |
| Michal IT Services Limited | Information & communication | 2023 |
| Michol Global Ltd | Hospitality | 2024 |
| Micklewright Investments Limited | Financial services | 2026 |
| Micro Brand Limited | Financial services | 2025 |
| Micro-X Limited | Information & communication | 2025 |
| Micronomy Ltd | Professional & scientific | 2022 |
| MID Cornwall Fasteners Ltd | Wholesale & retail | 2024 |
| MID Devon Fasteners Ltd | Wholesale & retail | 2024 |
| Middcab Limited | Information & communication | 2013 |
| Midec Decorating Ltd | Construction | 2024 |
| Midland House (Plymouth) 2025 Ltd | Real estate | 2025 |
| Midland House (Plymouth) Ltd | Real estate | 2025 |
| Midland House (Plymouth) Management Ltd | Real estate | 2025 |
| Midlands Cheap Cars Ltd | Wholesale & retail | 2015 |
| Midoritcg Ltd | Wholesale & retail | 2025 |
| Midrock Analysis Ltd | Information & communication | 2020 |
| Midships Cleaning Limited | Administrative & support | 2024 |
| Midtarget Property Management Limited | Households | 1988 |
| Migrant Social Integration CIC | Hospitality | 2025 |
| Migration Media Ltd | Other services | 2013 |
| MIK Property Management Ltd | Real estate | 2024 |
| Mike Cruickshank Publishing Ltd | Information & communication | 2012 |
| Mike Davies Associates Ltd | Professional & scientific | 2023 |
| Mike Dingle Consultancy Ltd | Professional & scientific | 2009 |
| Mike Flynn Coaching Ltd | Health & social care | 2016 |
| Mike Gilbert Carpentry Ltd | Construction | 2023 |
| Mike Jarvis Ltd | Construction | 2023 |
| Mike Knight Limited | Education | 2008 |
| Mike Ostler Garden & Property Services Limited | Administrative & support | 2022 |
| Mikutys 1 Limited | Construction | 2012 |
| Mikutyte Limited | Health & social care | 2018 |
| Mila's Bakehouse Ltd | Hospitality | 2020 |
| Mila's Bakery Ltd | Hospitality | 2020 |
| Mila's Plymouth Ltd | Hospitality | 2022 |
| Milehouse Villas Management Limited | Households | 2006 |
| Miliki Foods Limited | Manufacturing | 2025 |
| Military Marine Limited | Administrative & support | 2017 |
| Mill House Holdings Devon Ltd | Financial services | 2024 |
| Mill Meadow (Taunton) Management Co Limited | Households | 2010 |
| Millbay Tyres & Valeting Ltd | Wholesale & retail | 2020 |
| Millbay Tyres Ltd | Wholesale & retail | 2021 |
| Millbridge Property Development Ltd | Construction | 2010 |
| Millbrook Indian Ltd | Hospitality | 2022 |
| Millbrook Pharmacy Limited | Wholesale & retail | 2005 |
| Millennium Engineering Limited | Professional & scientific | 2006 |
| Miller Global Trading Ltd | Wholesale & retail | 2025 |
| Miller Lets Ltd | Hospitality | 2024 |
| Millfield Eco Projects Limited | Construction | 1990 |
| Millfields Community Economic Development Trust Community Interest Company | Administrative & support | 1998 |
| Millfields Inspired | Education | 2013 |
| Millhead (Properties) Limited | Real estate | 1989 |
| Millions of Vitamins Ltd | Wholesale & retail | 2026 |
| Milljay (NE) Ltd | Manufacturing | 2016 |
| Millrain Limited | Administrative & support | 2007 |
| Mills Cottages Limited | Households | 2020 |
| Mills Holdings SW Ltd | Financial services | 2020 |
| Milne & Co. Holdings Limited | Real estate | 2026 |
| Mimi & MAC Homeware Ltd | Wholesale & retail | 2023 |