| M Hale Joinery Ltd | Construction | 2021 |
| M Lloyd Property Ltd | Construction | 2026 |
| M Lloyd Services Ltd | Agriculture & fishing | 2022 |
| M W Carpenter Welding Limited | Manufacturing | 2003 |
| M&P Pharma Services Ltd | Financial services | 2022 |
| M.A.Seabridge&Sons Ltd | Transport & logistics | 2020 |
| M.H.G Motor Company Limited | Wholesale & retail | 2003 |
| M.K. Preece Excavations Ltd | Construction | 2003 |
| Macclesfield Propco Limited | Real estate | 2025 |
| Macenergie Limited | Energy | 2011 |
| Mackenzie & George Ltd | Manufacturing | 2012 |
| Macl Commissioning Management Ltd | Construction | 2025 |
| MAD Dog's Blades Limited | Manufacturing | 2023 |
| Madbergs Ltd | Professional & scientific | 2018 |
| Maelor Forest Nurseries Holdings Limited | Financial services | 2016 |
| Maelor Forest Nurseries Limited | Agriculture & fishing | 2004 |
| Magic Dragon Brewing Ltd | Manufacturing | 2025 |
| Magic Dragon Brewing Wrexham Ltd | Hospitality | 2019 |
| Magic Heating Limited | Agriculture & fishing | 2023 |
| Mahker Ltd | Wholesale & retail | 2021 |
| Maia Vitality Ltd | Health & social care | 2025 |
| Mainswell Ltd | Water & waste | 2024 |
| Maintel UK Limited | Information & communication | 2002 |
| Make a Point Limited | Administrative & support | 2018 |
| Make Waves Films Ltd | Information & communication | 2023 |
| Make Waves Limited | Information & communication | 2018 |
| Malcolm Harrison Auctions Limited | Other services | 2004 |
| Malvern Propco Limited | Real estate | 2025 |
| Manchester Vibes in the Area Limited | Wholesale & retail | 2026 |
| Mane Property Solutions Limited | Households | 2025 |
| Manuel Dredging Ltd | Construction | 2026 |
| Marbury Financial Limited | Professional & scientific | 2025 |
| Marbury Park Management Company Limited | Households | 2006 |
| Marina School of Dance Ltd | Education | 2020 |
| Mark James Cabinet Makers Limited | Manufacturing | 2014 |
| Mark Peplinski Technical Services Limited | Administrative & support | 2016 |
| Mark Turner Cameras Limited | Administrative & support | 2009 |
| Marlowe Court (Whitchurch) Management Limited | Households | 2004 |
| Marsdenmee Limited | Professional & scientific | 2016 |
| Marshall Exterior Cleaning Limited | Administrative & support | 2023 |
| Mary Malyon & Daughters Ltd | Real estate | 2024 |
| Masters Flooring Ltd | Wholesale & retail | 2010 |
| MAT and Education Finance Consultant Limited | Professional & scientific | 2023 |
| Matt Walker Engineering Ltd | Manufacturing | 2025 |
| Matthew Beech Holdings Limited | Financial services | 2023 |
| Matthew Beech Limited | Information & communication | 2023 |
| Matthew Ryan Investments Limited | Real estate | 2025 |
| Matthew Ryan Property Limited | Real estate | 2022 |
| Matthews Property Partners Limited | Real estate | 2022 |
| Mattison Properties Limited | Real estate | 2021 |
| MB Medical Writing Ltd | Professional & scientific | 2014 |
| Mcfour Group Limited | Extraterritorial | 2019 |
| Mcfour Limited | Construction | 1996 |
| Mcfour Plant Limited | Extraterritorial | 2019 |
| Mcgowan Grocott Land & Property Limited | Construction | 2022 |
| Mchjap Limited | Information & communication | 2010 |
| MD Aggregate Supplies Ltd | Wholesale & retail | 2016 |
| Mee-Fit Holdings Limited | Financial services | 2025 |
| Mee-Fit Limited | Arts & recreation | 2018 |
| Mee-Fit Shrewsbury Limited | Education | 2023 |
| Megji and Company Limited | Wholesale & retail | 1978 |
| Mercy and SON Limited | Transport & logistics | 2017 |
| Mere Properties Limited | Households | 2018 |
| Meredith Advisers Limited | Arts & recreation | 2014 |
| MG Electric Solutions Ltd | Construction | 2025 |
| Midan Investment Limited | Professional & scientific | 2009 |
| Midland Auto Factors Limited | Wholesale & retail | 1992 |
| Midland Shoe Imports Limited | Real estate | 1989 |
| Midway Truck Stop Ltd | Hospitality | 2017 |
| Mildmay Equine Limited | Arts & recreation | 2016 |
| Mildmay Farm & Stud Limited | Professional & scientific | 2000 |
| Milesix Ltd | Transport & logistics | 2025 |
| Mill House (WEM) Limited | Households | 1991 |
| Millenheath Farms Limited | Agriculture & fishing | 2015 |
| Millington Consultants Ltd | Professional & scientific | 2018 |
| Millward Farms Ltd | Agriculture & fishing | 2020 |
| Minet Limited | Information & communication | 2018 |
| Mjen Tech Services Limited | Professional & scientific | 2015 |
| MJH Automotive Limited | Financial services | 2022 |
| MJP Travel Ltd | Administrative & support | 2016 |
| MJR Pressure Washers Limited | Manufacturing | 2022 |
| Mm&D Land Ltd | Real estate | 2025 |
| Mobexx Holdings Ltd | Wholesale & retail | 2026 |
| Mobexx Ltd | Information & communication | 2008 |
| Mobexx-Ex Ltd | Wholesale & retail | 2026 |
| Mobxscan Ltd | Information & communication | 2011 |
| Mode Sports Ltd | Manufacturing | 2023 |
| Mole Music Ltd. | Arts & recreation | 2002 |
| Monarchbuildingcompany Ltd | Manufacturing | 2025 |
| Moneytomove Limited | Financial services | 2005 |
| MOO and Boom Limited | Wholesale & retail | 2023 |
| Moo's Coffee Bar Ltd | Hospitality | 2019 |
| MOP Media Limited | Administrative & support | 2009 |
| Moreton Wood Farm Ltd | Agriculture & fishing | 2017 |
| Morley Enterprises Ltd | Transport & logistics | 2026 |
| Morren Accountancy Limited | Professional & scientific | 2013 |
| Morris Evans Oils Limited | Extraterritorial | 1993 |
| Morus Business Advisors Limited | Professional & scientific | 2013 |
| Mosaic Wealth Management Limited | Financial services | 2024 |
| Moto 888 Limited | Wholesale & retail | 2020 |