| M.Y.K-Hoopooe Limited | Hospitality | 2021 |
| M/Y Carz Ltd | Administrative & support | 2015 |
| M1ND CIC | Education | 2019 |
| M2 Building Limited | Construction | 2017 |
| M22NCH Ltd | Real estate | 2023 |
| M2I2 Limited | Information & communication | 2025 |
| M2M Construction Group Ltd | Financial services | 2020 |
| M2M Joinery Limited | Manufacturing | 2015 |
| M2M Properties Limited | Real estate | 2021 |
| M2M Windows & Doors Ltd | Manufacturing | 2020 |
| M3 Cuts Limited | Other services | 2025 |
| M3 Lettings Property Services Limited | Real estate | 2014 |
| M32 Elite Ltd | Education | 2025 |
| M33MA Limited | Construction | 2020 |
| M4T Properties Limited | Real estate | 2024 |
| M8 Services Ltd | Wholesale & retail | 2020 |
| MA & HG Consulting Ltd | Professional & scientific | 2024 |
| MA & KP Ltd | Health & social care | 2019 |
| MA & PA Shelley Limited | Real estate | 2023 |
| MA A2Z Ltd | Transport & logistics | 2024 |
| MA Car Services Ltd | Wholesale & retail | 2025 |
| MA Care Ltd | Health & social care | 2022 |
| MA Consultancy Ltd | Education | 2021 |
| MA Education Consultancy CIC | Education | 2019 |
| MA Egerton's Ltd | Hospitality | 2012 |
| MA EST Limited | Real estate | 2022 |
| MA Estate Builder Ltd | Construction | 2025 |
| MA Estates and Property Services Ltd | Real estate | 2024 |
| MA Good Guys Ltd | Wholesale & retail | 2018 |
| MA Warehousing Ltd | Transport & logistics | 2024 |
| MAA JI Limited | Hospitality | 2020 |
| Maad Studio Ltd | Professional & scientific | 2021 |
| MAAG2 Ltd | Hospitality | 2026 |
| Maal Propco Ltd | Real estate | 2020 |
| Maan Somali Mental Health Sheffield | Health & social care | 2008 |
| Maandeeq Cafe Ltd | Hospitality | 2025 |
| Maap Medical Limited | Real estate | 2018 |
| Maawal Ltd | Health & social care | 2023 |
| Mabasa Health Care Limited | Health & social care | 2013 |
| Mabelspace Ltd | Professional & scientific | 2023 |
| Mabico Ltd | Construction | 2013 |
| Mablethorpe Care Limited | Health & social care | 2017 |
| Mabo Consulting Ltd | Professional & scientific | 2008 |
| MAC Cleaning Services Ltd | Administrative & support | 2025 |
| MAC F&B Ltd | Hospitality | 2024 |
| MAC Finance Limited | Other services | 2018 |
| MAC Imports Limited | Wholesale & retail | 2004 |
| MAC Office Supplies Ltd | Administrative & support | 2004 |
| MAC Rendering Ltd | Construction | 2020 |
| MAC Tools Sheffield Limited | Wholesale & retail | 2025 |
| MAC Transit Parts Ltd | Wholesale & retail | 2025 |
| Mac'Ants Abrasives Limited | Manufacturing | 1977 |
| Mac's Traders Ltd | Construction | 2024 |
| Maca Rendering Ltd | Construction | 2018 |
| Maca Workwear Ltd | Wholesale & retail | 2019 |
| Macalloy Cast Products Limited | Manufacturing | 2011 |
| Macalloy Limited | Manufacturing | 2009 |
| Macaw Store Limited | Wholesale & retail | 2025 |
| Macclesfield Mini Market Limited | Wholesale & retail | 2025 |
| Macclesfield Superstore Limited | Wholesale & retail | 2026 |
| Macdonald Joinery and Construction Ltd | Construction | 2003 |
| Maceo Ltd. | Professional & scientific | 2018 |
| Mach One (Holdings) Limited | Professional & scientific | 1998 |
| Mach One (International) Limited | Manufacturing | 1991 |
| Machen & MAW Ltd | Construction | 2014 |
| Machine Knives and Blades Ltd | Wholesale & retail | 2014 |
| Machine Mind Solutions Ltd | Information & communication | 2023 |
| Machine Reflex Limited | Information & communication | 2014 |
| Machineworks Limited | Information & communication | 2002 |
| Machon Estates Ltd | Real estate | 2024 |
| Machon Management Company Limited | Households | 2001 |
| Mack Construction Ltd | Construction | 2017 |
| Mack RAE Limited | Real estate | 2003 |
| Mackay Kennedy Productions Limited | Information & communication | 2014 |
| Mackenzie Cain IT Limited | Information & communication | 2011 |
| Mackenzie Hodgson Ltd | Administrative & support | 2017 |
| Mackenzie Morgan Limited | Professional & scientific | 2005 |
| Mackenzie Spencer Limited | Professional & scientific | 2021 |
| Mackron Limited | Professional & scientific | 2005 |
| Mackworth Travels Ltd | Transport & logistics | 2024 |
| Maclean & Beyond Ltd | Wholesale & retail | 2022 |
| Maclure Properties Ltd | Real estate | 2019 |
| Macmillan QS Limited | Professional & scientific | 2014 |
| Macmor Consulting Limited | Professional & scientific | 2020 |
| Maco Corporation UK Ltd | Manufacturing | 2026 |
| Macpherson Investments Ltd | Real estate | 2024 |
| Macs Consultants Limited | Professional & scientific | 2024 |
| Mactech Global Ventures Ltd | Wholesale & retail | 2025 |
| Mactombolo Ltd | Transport & logistics | 2025 |
| Macvein Ltd | Health & social care | 2026 |
| MAD Boss World Music Productions Limited | Information & communication | 2024 |
| MAD Dog Marketing Limited | Wholesale & retail | 2004 |
| MAD Monkey Merchandise Limited | Wholesale & retail | 2018 |
| Madandkat Holdings Limited | Financial services | 2015 |
| Madandkat Properties Limited | Real estate | 2016 |
| Madani Memorials S.Yorks Limited | Manufacturing | 2019 |
| Maddison Hair Salon Limited | Other services | 2025 |
| Made by an Englishman Limited | Manufacturing | 2016 |
| Made by Jonty Limited | Hospitality | 2010 |
| Made Co Group Limited | Hospitality | 2026 |