| M.W.H. & H. Ward Estates Limited | Agriculture & fishing | 1990 |
| M.Y Connect UK Ltd | Wholesale & retail | 2015 |
| M.Y Products & Services Limited | Other services | 2021 |
| M.Y. Trondex Limited | Professional & scientific | 1936 |
| M.Y.Sum Trading Limited | Hospitality | 2022 |
| M1 Foam & Chrome Detailing Ltd | Other services | 2018 |
| M1 Homes Limited | Real estate | 2025 |
| M14 Innovations Limited | Water & waste | 2024 |
| M1DECO Ltd | Construction | 2018 |
| M2 Developments Ltd | Real estate | 2024 |
| M2 Flooring Limited | Construction | 1978 |
| M2 Property Invest Limited | Administrative & support | 2016 |
| M25 Motors & Repair Ltd | Health & social care | 2024 |
| M2C International Group Co., Ltd | Wholesale & retail | 2020 |
| M2M Investments Limited | Real estate | 2024 |
| M3 Agency Wales Ltd | Professional & scientific | 2025 |
| M3 Dental Limited | Health & social care | 2025 |
| M3 Nature World Ltd | Information & communication | 2018 |
| M3 Transport Ltd | Other services | 2019 |
| M3EENDIGITAL Ltd | Manufacturing | 2025 |
| M4 Digital Group Ltd | Information & communication | 2013 |
| M4 Freight Ltd | Transport & logistics | 2019 |
| M4 Industrial Estates Limited | Real estate | 2019 |
| M4 Mortgages Ltd | Financial services | 2015 |
| M7 Asset Management Limited | Financial services | 2023 |
| MA & ST Hill Limited | Health & social care | 2011 |
| MA Argabi Ltd | Wholesale & retail | 2025 |
| MA Baker LOO Limited | Administrative & support | 2024 |
| MA Business Hub Limited | Information & communication | 2019 |
| MA Capital Ltd | Construction | 2018 |
| MA Dynamic Trading Limited | Wholesale & retail | 2025 |
| MA Engineering Solutions Limited | Professional & scientific | 2014 |
| MA Grocery Store Limited | Wholesale & retail | 2022 |
| MA Groundworks and Landscaping Limited | Construction | 2012 |
| MA Investments Group Ltd | Professional & scientific | 2021 |
| MA Ltd Group Ltd | Information & communication | 2025 |
| MA Luisa Taguran Ltd | Wholesale & retail | 2025 |
| MA Niel Phoenix Limited | Financial services | 2016 |
| MA Niel UK Limited | Financial services | 2016 |
| MA Property Sourcing Ltd | Administrative & support | 2023 |
| MA Traderz Ltd | Wholesale & retail | 2022 |
| MA Wealth Management Limited | Real estate | 2024 |
| Ma'Ana Group Ltd | Wholesale & retail | 2017 |
| MAA Digital Solutions Ltd | Wholesale & retail | 2023 |
| Maac Limited | Construction | 2015 |
| Maaf Business Group Ltd | Wholesale & retail | 2025 |
| Maaif Botanica Limited | Wholesale & retail | 2023 |
| Maalik Trading Ltd | Wholesale & retail | 2026 |
| Maans Craft Limited | Wholesale & retail | 2026 |
| Maasi's Ltd | Hospitality | 2019 |
| Maath Constructions Ltd | Construction | 2022 |
| MAB Media Global Ltd | Information & communication | 2025 |
| Maba Holdings Ltd | Real estate | 2021 |
| Mabby PUB Company Limited | Hospitality | 2015 |
| Mabe Limited | Professional & scientific | 2019 |
| Mabel Estates Limited | Administrative & support | 2018 |
| Mabli Knits Limited | Wholesale & retail | 2016 |
| Mably Consulting Limited | Professional & scientific | 2023 |
| Mably Holdings Limited | Real estate | 2023 |
| Mably Investment Limited | Construction | 1994 |
| Mably Surgical Limited | Health & social care | 2025 |
| Mabrolez Solutions Ltd | Wholesale & retail | 2021 |
| Mabs Barnet Limited | Wholesale & retail | 2020 |
| MAC and Gray Limited | Education | 2021 |
| MAC Assist Ltd | Professional & scientific | 2019 |
| MAC Digital Group Ltd | Administrative & support | 2022 |
| MAC Electrical 247 Ltd | Construction | 2017 |
| MAC Property Group Ltd | Construction | 2019 |
| MAC Scaffolding (Cardiff) Ltd | Construction | 2011 |
| MAC Scaffolding Limited | Construction | 2015 |
| MAC Star Services Ltd | Construction | 2020 |
| Mac-Ed Training Ltd | Education | 2019 |
| Mac.Lovingg Limited | Hospitality | 2025 |
| Macaan Vending Limited | Hospitality | 2025 |
| Macao Industry Ltd | Wholesale & retail | 2025 |
| Macaulay Clift Associates Limited | Health & social care | 2014 |
| Macaulay Hewitt Ltd | Real estate | 2017 |
| Macca Care Ltd | Health & social care | 2015 |
| Maccasa Limited | Real estate | 2024 |
| Macchiato Media Ltd | Information & communication | 2023 |
| Macd IT Ltd | Information & communication | 2011 |
| Mace Construct Group Limited | Construction | 2026 |
| Macelariaromaneascalanasusifinu Ltd | Manufacturing | 2020 |
| Maceluka | Professional & scientific | 2025 |
| Macfas Ltd | Energy | 2023 |
| Macgregor Consultancy Limited | Administrative & support | 2009 |
| Mache Confederation Ltd | Information & communication | 2023 |
| Mache Money ENT Ltd | Wholesale & retail | 2018 |
| Machi Cleaning Company Limited | Administrative & support | 2025 |
| Machinery Movements & Crane Hire Limited | Administrative & support | 2003 |
| Machnc Limited | Manufacturing | 2016 |
| Macho Republic CIC | Information & communication | 2025 |
| Machur Limited | Professional & scientific | 2023 |
| Macice Investments Ltd | Wholesale & retail | 2015 |
| Macies GED Ltd | Hospitality | 2025 |
| Maciomhair Telecomms Ltd | Information & communication | 2012 |
| Mack Gentlemen's Grooming (Bar) Ltd | Hospitality | 2025 |
| Mack Gentlemen's Grooming Ltd | Other services | 2018 |
| Mackay & Mckenzie Financial Services Ltd | Financial services | 2021 |
| Mackenzie & Hartley Tools Limited | Wholesale & retail | 2019 |