| Mac's Motors Limited | Wholesale & retail | 2019 |
| Macarb Holdings Ltd | Financial services | 2024 |
| Macarb Investments Ltd | Financial services | 2022 |
| Macauto Limited | Manufacturing | 1994 |
| Macbrook Developments Ltd | Financial services | 2024 |
| Macbrook Training Academy Ltd | Education | 2025 |
| Macdougall Property Limited | Construction | 2016 |
| Mace Residential Limited | Real estate | 2016 |
| Macfarlane Simpson Associates Ltd | Real estate | 2025 |
| Macg Ltd | Construction | 2021 |
| Macgregor Farming Partnership LLP | | 2025 |
| Machaba International Limited | Transport & logistics | 2019 |
| Machine & Systems Design Limited | Professional & scientific | 2020 |
| Machinery Installations (Birmingham) Limited | Transport & logistics | 1987 |
| Macie Hitter Racing Ltd | Arts & recreation | 2021 |
| Macinnes Holdings Ltd | Other services | 2026 |
| Mack Farming Company Limited | Agriculture & fishing | 2014 |
| Mackay Lake Property Limited | Real estate | 2018 |
| Mackenzie Education Ltd | Education | 2025 |
| Mackenzie Grill Ltd | Hospitality | 2025 |
| Mackenzie TM Ltd | Construction | 2022 |
| Mackie Consumer Marketing Co. Limited(The) | Real estate | 1978 |
| Maclynn Limited | Information & communication | 1996 |
| Macmaddi Ltd | Real estate | 2020 |
| Macmoran Recruitment Limited | Administrative & support | 2025 |
| Macrow Heating Ltd | Construction | 2025 |
| MAD 2 Aviation Ltd | Other services | 2017 |
| MAD Drylining Ltd | Construction | 2017 |
| MAD Enterprises (UK) Ltd | Information & communication | 2013 |
| Madara Ltd | Hospitality | 2025 |
| Madder Properties Limited | Real estate | 2021 |
| Maddison and Morgan (UK) Ltd | Professional & scientific | 2012 |
| Maddison Graphic Limited | Professional & scientific | 2023 |
| Maddison Rail & Construction Limited | Administrative & support | 2016 |
| Made by Launch Ltd | Information & communication | 2026 |
| Made by the Box Ltd | Professional & scientific | 2024 |
| Made Inc Ltd | Other services | 2021 |
| Made of Data Ltd | Professional & scientific | 2024 |
| MADE2AID Ltd | Information & communication | 2012 |
| Madefly Ltd | Information & communication | 2024 |
| Madeforshine Limited | Administrative & support | 2023 |
| Madeleines of Aylsham Limited | Hospitality | 2023 |
| Madhat Media Limited | Professional & scientific | 2018 |
| Madina 2026 Ltd | Manufacturing | 2026 |
| Madison Construction (EA) Ltd | Construction | 2021 |
| Madisons (North Walsham) Limited | Hospitality | 2003 |
| Madone Consulting Company Limited | Professional & scientific | 2020 |
| Madone Management LLP | | 2023 |
| Madras Indian Cuisine Limited | Hospitality | 2018 |
| Madrsk Holdings Ltd | Financial services | 2024 |
| Madx Ltd | Wholesale & retail | 2013 |
| MAE Cosmetics Ltd | Other services | 2016 |
| MAE Wellness Ltd. | Other services | 2023 |
| Maeer Associates Limited | Professional & scientific | 2010 |
| Maevy and Associates Ltd | Professional & scientific | 2026 |
| Mafij Consulting Ltd | Administrative & support | 2017 |
| Maftuna Limited | Wholesale & retail | 2025 |
| MAG Group Limited | Professional & scientific | 2002 |
| Maganis Ltd | Administrative & support | 2022 |
| Magata Holdings Limited | Professional & scientific | 2007 |
| Magdalen Gates Nursery Limited | Health & social care | 2025 |
| Magdalen Medical Supplies Ltd | Wholesale & retail | 2024 |
| Magdalen Norwich Ltd | Real estate | 2018 |
| Magdalen Pharma Ltd | Wholesale & retail | 2024 |
| Magdalen Road Commercial Property Ltd | Real estate | 2018 |
| Magdalen Road Store Norwich Ltd | Wholesale & retail | 2024 |
| Maged Hussien Limited | Health & social care | 2016 |
| Magel Ltd | Information & communication | 2026 |
| Magellan Consulting (Emea) Ltd | Professional & scientific | 2018 |
| Maggie Todd Limited | Professional & scientific | 2021 |
| Maggie's Feel Good Food Ltd. | Hospitality | 2017 |
| Magic 1997 Care Services Ltd | Health & social care | 2024 |
| Magic Blade Music Limited | Arts & recreation | 2019 |
| Magic Catering Ltd | Manufacturing | 2024 |
| Magicsauce Online Ltd | Information & communication | 2021 |
| Magik Clippers Ltd | Other services | 2018 |
| Maginfica Global Ltd | Wholesale & retail | 2019 |
| Magma Properties Limited | Construction | 1996 |
| Magnet Shipping (UK) Ltd | Transport & logistics | 2012 |
| Magnificent Stuff Limited | Professional & scientific | 2014 |
| Magnik Holdings Ltd | Financial services | 2026 |
| Magnolia Beauty&Beyond Ltd | Wholesale & retail | 2020 |
| Magnolia Square Limited | Professional & scientific | 2004 |
| Magnolias Restaurant (Taverham) Limited | Hospitality | 2003 |
| Magnus Group Limited | Transport & logistics | 1994 |
| Magnus Whyte Property Developments Limited | Construction | 2003 |
| Magoro Ltd | Real estate | 2020 |
| Magpies Commercial Ltd | Arts & recreation | 2024 |
| Magtag UK Distribution Ltd. | Wholesale & retail | 2025 |
| MAH2 Limited | Administrative & support | 2016 |
| Maha Shames Limited | Health & social care | 2025 |
| Mahar Bros Ltd | Hospitality | 2026 |
| Mahar Coffee Ltd | Hospitality | 2019 |
| Mahb Capital Limited | Real estate | 2010 |
| Mahle Limited | Hospitality | 2022 |
| Mahoney Green Limited | Real estate | 2023 |
| Mahtab Caterers Ltd | Hospitality | 2017 |
| Mahvash Rugs Ltd | Wholesale & retail | 2024 |
| Maiasoft Software Limited | Information & communication | 2006 |
| Maia’S Vintage Wholesale Ltd | Wholesale & retail | 2024 |