| Mabu International Limited | Wholesale & retail | 2025 |
| Mabwo Limited | Health & social care | 2014 |
| MAC Aerials and Satellites Ltd | Information & communication | 2019 |
| MAC CC Group Limited | Professional & scientific | 2019 |
| MAC CC Holdings Limited | Professional & scientific | 2023 |
| MAC Cleaning Limited | Administrative & support | 2022 |
| MAC Construction Consultants Limited | Construction | 2012 |
| MAC Design Consultancy Services Limited | Construction | 2012 |
| MAC Project Management Limited | Construction | 2012 |
| Macalpha Services Ltd | Administrative & support | 2026 |
| Macangel & Associates Limited | Construction | 2023 |
| Macarie Financial Limited | Professional & scientific | 2019 |
| Macarius Investment Group Limited | Real estate | 2021 |
| Macarthur Kennedy Consulting Ltd | Professional & scientific | 2024 |
| Macavity Limited | Information & communication | 2021 |
| Macavity Press Limited | Information & communication | 2023 |
| Macbeth Estates Ltd | Real estate | 2025 |
| Macharia Limited | Health & social care | 2022 |
| Machroar Streetwear Ltd | Wholesale & retail | 2024 |
| Macian Music Limited | Manufacturing | 2018 |
| Macilla Afrik Designs Ltd | Wholesale & retail | 2023 |
| Macintyre Academies | Education | 2012 |
| Macintyre Care | Education | 1966 |
| Macintyre Hudson Advisory Services LLP | | 2010 |
| Macintyre Hudson Holdings Limited | Professional & scientific | 1999 |
| Macintyre Hudson Limited | Administrative & support | 1985 |
| Macintyre Hudson LLP | | 2005 |
| Macintyre Hudson Treasury Limited | Professional & scientific | 2013 |
| Macintyre Law (DM) Ltd | Administrative & support | 2023 |
| Macintyre Law Limited | Professional & scientific | 2009 |
| Macintyre Nominees | Professional & scientific | 1989 |
| Macioszek Ltd | Financial services | 2025 |
| Mackenzie Investments Ltd | Real estate | 2021 |
| Mackenzie Nail Company Limited | Financial services | 2017 |
| Mackenzie RLC Ltd | Real estate | 2024 |
| Mackles Care Limited | Health & social care | 2025 |
| Maclean Visuals Limited | Wholesale & retail | 2023 |
| Macloc Limited | Construction | 2021 |
| Maclow Property Management Ltd | Households | 2025 |
| Macnica UK Limited | Professional & scientific | 2015 |
| Macrae Alterations Limited | Transport & logistics | 2003 |
| Macrico Services Ltd | Professional & scientific | 2010 |
| Macs and Sons Limited | Construction | 2015 |
| Macson Investments Limited | Professional & scientific | 2020 |
| Macspudz Ltd | Hospitality | 2025 |
| MAD 4 Motocross Ltd | Wholesale & retail | 2006 |
| MAD Performers Ltd | Arts & recreation | 2026 |
| MAD4 Limited | Wholesale & retail | 2017 |
| Madbear Ltd | Financial services | 2026 |
| Madd Transport Service Ltd | Transport & logistics | 2018 |
| Maddock Street Construction Limited | Construction | 2019 |
| Made Consulting Limited | Households | 2022 |
| Made in England (Estates) Limited | Real estate | 2019 |
| Made Investors Limited | Real estate | 2025 |
| Made With Mummy Love Ltd | Manufacturing | 2014 |
| Madeira Estates Limited | Real estate | 2022 |
| Maden Properties Ltd | Real estate | 2025 |
| Madhava Spirit Ltd | Professional & scientific | 2026 |
| Madhen Productions Limited | Administrative & support | 2008 |
| Madi MAI Engineering Limited | Professional & scientific | 2014 |
| Madilo Limited | Wholesale & retail | 2020 |
| Madmoldovans Ltd | Hospitality | 2023 |
| Madni Halal Meat Milton Keynes Ltd | Wholesale & retail | 2026 |
| Madrose Landscapes Ltd | Administrative & support | 2022 |
| Mads Tech Ltd | Information & communication | 2020 |
| Madson Properties Limited | Real estate | 2018 |
| MAE Limited | Information & communication | 2006 |
| Maester Magic Ltd | Wholesale & retail | 2025 |
| Maestro Property Group Ltd | Real estate | 2025 |
| Maestro Publishing Ltd | Information & communication | 2019 |
| Maeve Liffey Management Limited | Other services | 2016 |
| Maeve M Jackson Mortgages Ltd | Financial services | 2025 |
| Mafiacuts Limited | Other services | 2019 |
| Mafifa Ltd | Extraterritorial | 2023 |
| Mafuta IT Solutions Ltd | Information & communication | 2015 |
| Maga MED Limited | Health & social care | 2026 |
| Magard Limited | Extraterritorial | 2010 |
| Magaya Health Care Limited | Health & social care | 2022 |
| Magbuck Cleaning Services Ltd | Administrative & support | 2026 |
| Magellan Consultancy Services Ltd | Professional & scientific | 2003 |
| Magellantide Digital Technology Ltd | Wholesale & retail | 2025 |
| Magenta Line Limited | Professional & scientific | 2014 |
| Magethy Ltd | Health & social care | 2020 |
| Magic Acupuncture Ltd | Health & social care | 2021 |
| Magic Cube Ltd | Real estate | 2023 |
| Magic Key Properties Ltd | Real estate | 2024 |
| Magic Maids Ltd | Administrative & support | 2025 |
| Magic Valeting (Watford) Limited | Wholesale & retail | 2018 |
| Magic Valeting Centre (City MK) Ltd | Other services | 2008 |
| Magic Voices Limited | Arts & recreation | 2013 |
| Magical Mumma Ltd | Manufacturing | 2025 |
| Magical Way Limited | Professional & scientific | 2024 |
| Magna Development Group Ltd | Real estate | 2020 |
| Magnetoflow Ltd | Other services | 2024 |
| Magnifico Property Ltd | Real estate | 2023 |
| Magnolia Curtains Ltd | Manufacturing | 2023 |
| Magnolia Shop (MK) Ltd | Wholesale & retail | 2021 |
| Magnolia Tree Consultancy Limited | Professional & scientific | 2023 |
| Magnum BRO Ltd | Transport & logistics | 2018 |
| Magnum Consulting Limited | Information & communication | 2008 |