| MAC Employees Limited | Other services | 2016 |
| MAC Griff Quarry Limited | Financial services | 2025 |
| MAC Nuneaton Quarry Limited | Mining & quarrying | 2017 |
| MAC Quarries Limited | Financial services | 2014 |
| MAC Recycling Limited | Water & waste | 2009 |
| MAC Remediation Limited | Financial services | 2025 |
| MAC Skip Hire Limited | Water & waste | 2015 |
| MAC Skips Limited | Water & waste | 2016 |
| MAC Waste Management UK Limited | Water & waste | 2015 |
| Macdonald Installations Limited | Construction | 1996 |
| Machine Advocate Limited | Wholesale & retail | 2020 |
| Machine for Music Ltd | Extraterritorial | 2011 |
| Machinery Engineering Limited | Manufacturing | 1992 |
| Machinery Engineering Services Limited | Administrative & support | 1984 |
| Mackart Engineering Ltd | Manufacturing | 2016 |
| Mackay'B Ltd | Information & communication | 2015 |
| Mackwell Electronics Limited | Manufacturing | 1979 |
| Mackwell Health Limited | Health & social care | 2021 |
| Macram Services Ltd | Administrative & support | 2019 |
| Macroedustore (Mestore) Ltd | Wholesale & retail | 2025 |
| Mactcg Ltd | Information & communication | 2026 |
| Macxavier Chirwa Ltd | Other services | 2024 |
| MAD Production U.K. Ltd | Hospitality | 2024 |
| Madari Halal Meats Limited | Wholesale & retail | 2021 |
| Made in Group Limited | Information & communication | 2022 |
| Made in Poland Events Ltd | Administrative & support | 2026 |
| Made in the Midlands Limited | Other services | 2011 |
| Made in the North West Limited | Other services | 2024 |
| Made in the South East Limited | Other services | 2018 |
| Madeley Manor Developments Limited | Construction | 2022 |
| Madentiq Ltd | Health & social care | 2025 |
| Madni Food Products Ltd | Manufacturing | 2010 |
| Madnmean Limited | Wholesale & retail | 2023 |
| Mady Health Limited | Health & social care | 2011 |
| Maecon Builders Limited | Construction | 2025 |
| Maer&G Ltd | Construction | 2024 |
| Magar Properties Ltd | Real estate | 2024 |
| Magg Group Ltd | Construction | 2010 |
| Magic Scissors Walsall Ltd | Other services | 2024 |
| Magiled Ltd | Manufacturing | 2021 |
| Magna Care Services Ltd | Health & social care | 2016 |
| Magnetism Ltd | Wholesale & retail | 2024 |
| Magnolia Court (Romford) RTM Company Limited | Households | 2020 |
| Magnolia Rentals Limited | Real estate | 2020 |
| Mago Group Ltd | Wholesale & retail | 2023 |
| MAH Logistics Ltd | Transport & logistics | 2023 |
| Maha Eyes Limited | Health & social care | 2019 |
| Maha Eyes Properties Ltd | Real estate | 2023 |
| Mahadev OM Ltd | Wholesale & retail | 2026 |
| Mahan Movers Limited | Transport & logistics | 2025 |
| Mahi Sweets and Bakers Ltd | Manufacturing | 2023 |
| Mahir Trading Limited | Wholesale & retail | 2022 |
| Mahn Limited | Information & communication | 2016 |
| Mahroze Ltd | Wholesale & retail | 2019 |
| Maid to Perfection YJ Ltd | Administrative & support | 2025 |
| Maidah Realty Limited | Real estate | 2026 |
| Mailboxes (GB) Limited | Wholesale & retail | 2002 |
| Maimedia Productions Limited | Professional & scientific | 2025 |
| Main Denserv Limited | Health & social care | 2023 |
| Mainstay Property Holdings Limited | Financial services | 2021 |
| Mainstay Recruitment Solutions Ltd | Administrative & support | 2015 |
| Maison Build Ltd | Construction | 2017 |
| Maison Luxe Furniture Ltd | Wholesale & retail | 2024 |
| Maison Vitale Aesthetics and Colonics Limited | Health & social care | 2026 |
| Maisydaisy Florist Ltd | Wholesale & retail | 2022 |
| Majella Rose Ltd | Wholesale & retail | 2022 |
| Majero Ltd | Information & communication | 2016 |
| Majestic Event Hire Limited | Extraterritorial | 2018 |
| Majestic Finishing Limited | Manufacturing | 2025 |
| Majhail Express Ltd | Transport & logistics | 2024 |
| Majhe Side Ltd | Wholesale & retail | 2025 |
| Major Transport Group Ltd | Transport & logistics | 2017 |
| Majorfax Sourcing Limited | Wholesale & retail | 2016 |
| MAK Assets Ltd | Construction | 2016 |
| MAK Business Limited | Administrative & support | 2026 |
| MAK Cargo Ltd | Transport & logistics | 2023 |
| MAK Halal Walsall Ltd | Hospitality | 2021 |
| MAK Law Limited | Professional & scientific | 2012 |
| MAK Legal Ltd | Professional & scientific | 2019 |
| Makafui Care Ltd | Health & social care | 2018 |
| Makar Investments Ltd | Real estate | 2025 |
| Makcameras Ltd | Wholesale & retail | 2024 |
| Make More Community C.I.C. | Information & communication | 2023 |
| Makh Properties Limited | Real estate | 2023 |
| Making Sense Creative CIC | Education | 2026 |
| Makkah Foods Europe Ltd | Wholesale & retail | 2024 |
| Makkhanwala Ltd | Manufacturing | 2026 |
| MAL Education Ltd | Education | 2023 |
| Malayah & Co. Events Ltd | Administrative & support | 2025 |
| Malb Property Limited | Real estate | 2023 |
| Malbank Coaches Limited | Transport & logistics | 2025 |
| Malbank Limited | Transport & logistics | 2004 |
| Male Hairdressing & Lifestyle Coleshill Ltd | Other services | 2023 |
| Male Hairdressing & Lifestyle Tamworth Ltd | Other services | 2023 |
| Malgos Ltd | Transport & logistics | 2025 |
| Malhi MS Builder Limited | Construction | 2024 |
| Malibu Tanning Ltd | Other services | 2026 |
| Malik Motors PVT Ltd | Wholesale & retail | 2019 |
| Mall Estates Limited | Real estate | 2013 |
| Mallett & Sons Property Ltd | Real estate | 2025 |