| Major Group Management Services Ltd | Financial services | 2023 |
| MAK Merch UK Ltd | Wholesale & retail | 2024 |
| Make Digital Limited | Information & communication | 2021 |
| Make IT Sparkle Cleaning Ltd | Administrative & support | 2020 |
| Make New Traditions Ltd | Information & communication | 2024 |
| Makelsan Yachting Ltd | Extraterritorial | 2021 |
| Making Connections (Isle of Wight) Ltd | Education | 2005 |
| Making the Grade Ltd | Education | 2020 |
| Makkaj Perfumes UK Limited | Wholesale & retail | 2025 |
| Makot Ltd | Health & social care | 2021 |
| Maksymilian Delivery Ltd | Transport & logistics | 2024 |
| Malago Coffee Ltd | Wholesale & retail | 2025 |
| Malbroomproperty Ltd | Real estate | 2024 |
| Malcolm Bevan Limited | Other services | 2021 |
| Malcolm Perry Aldershot Social Landlord | Real estate | 2023 |
| Maldiva Clinic Limited | Other services | 2023 |
| Maley Properties Ltd | Real estate | 2022 |
| Malik Faisal Business Developers Limited | Professional & scientific | 2013 |
| Mall Property Management (IOW) Limited | Households | 2005 |
| Mallard Grange Residents Association Limited | Real estate | 1997 |
| Mallett & Daughters Ltd | Transport & logistics | 2026 |
| Mallett Transport Services Limited | Transport & logistics | 2009 |
| Maloney Clothing Ltd | Wholesale & retail | 2026 |
| Malosa Mews Ltd | Real estate | 2021 |
| Malpas Cottage Ltd | Hospitality | 2019 |
| Malpas Court Social Enterprise Ltd | Hospitality | 2010 |
| Malpas Curry Ltd | Hospitality | 2019 |
| Malpas Minibus Hire Limited | Transport & logistics | 2011 |
| Malpas Plumbing & Heating Solutions Ltd | Extraterritorial | 2018 |
| Mami Maggie’S Recipes Ltd | Hospitality | 2023 |
| Mamthoe Healthcare Ltd | Health & social care | 2024 |
| Mamu's Chaii Limited | Manufacturing | 2023 |
| Manage and Construct Limited | Professional & scientific | 2025 |
| Management Solutions (Wales) Limited | Extraterritorial | 2007 |
| Manat Bites Ltd | Hospitality | 2024 |
| Mandalay Investments Limited | Construction | 1996 |
| Mandalay Property Developments Ltd | Construction | 2018 |
| Manea Ltd | Transport & logistics | 2025 |
| Manergen Limited | Energy | 2025 |
| Manesis Search & Selection Ltd | Administrative & support | 2013 |
| Mango House Ltd | Hospitality | 2025 |
| Mango Monkeys Ltd | Real estate | 2021 |
| Manic Mechanics Newport Ltd. | Wholesale & retail | 2013 |
| Manik Social Care Counts Ltd | Health & social care | 2024 |
| Manisc Holdings Limited | Financial services | 2022 |
| Maniver Hussain ALI Limited | Transport & logistics | 2015 |
| Mankal Medical Limited | Health & social care | 2017 |
| Manna Express Ltd | Hospitality | 2025 |
| Manning Travel Limited | Administrative & support | 1992 |
| Manon Carpenter Ltd | Information & communication | 2015 |
| Manorbrook Media Limited | Information & communication | 2010 |
| Manshika Ltd | Real estate | 2025 |
| Mansoor Barbers Ltd | Other services | 2023 |
| Mantis Investments Ltd | Real estate | 2020 |
| Manufacturing Performance Solutions Limited | Professional & scientific | 2021 |
| Manzoor Ahmad Limited | Transport & logistics | 2023 |
| Maono Ltd | Professional & scientific | 2016 |
| Maranatha (Isle of Wight) Management Limited | Other services | 2005 |
| Marc Bolton Excavations & Groundworks Limited | Construction | 2014 |
| Marcel Ngogbehei Center for Cancer Education and Care Ltd | Education | 2025 |
| Marco Polo Trans Ltd | Transport & logistics | 2016 |
| Marcus Rickard Agricultural Services Ltd | Agriculture & fishing | 2015 |
| Marenghi's Restaurant Limited | Hospitality | 2023 |
| Margobull Ltd | Transport & logistics | 2019 |
| Marhaven Limited | Real estate | 1988 |
| Maria & Sons Ltd | Extraterritorial | 2020 |
| Mariam and Noshine Property Ltd | Real estate | 2026 |
| Mariappan Ltd | Health & social care | 2024 |
| Marina Court Management Limited | Households | 1985 |
| Marina Rentals Ltd | Real estate | 2022 |
| Marine Centre (Cardiff) Limited | Real estate | 1972 |
| Marine Data Systems Limited | Manufacturing | 2004 |
| Marine GAS Solutions Ltd | Manufacturing | 2021 |
| Marion Autolock Ltd | Wholesale & retail | 2023 |
| Marisa Valemma Limited | Health & social care | 2020 |
| Maritime Technology Solutions Ltd | Information & communication | 2024 |
| Marizmic Investments Limited | Financial services | 2025 |
| Mark 2 (Estate Agents) Ltd | Real estate | 2018 |
| Mark Anthony Hughes Ltd | Construction | 2020 |
| Mark Bebbington Services Limited | Transport & logistics | 2019 |
| Mark Coburn Vehicle Repairs Limited | Wholesale & retail | 2011 |
| Mark Evans Flooring Ltd | Construction | 2016 |
| Mark Jones Transformational Mentoring Limited | Health & social care | 2017 |
| Mark Robinson Maritime Consultants Ltd. | Extraterritorial | 2015 |
| Mark Sansom Engineering Limited | Manufacturing | 2015 |
| Marketingmotor Limited | Professional & scientific | 2019 |
| Markham Marine Services Ltd | Wholesale & retail | 2018 |
| Markt Trading Ltd | Wholesale & retail | 2025 |
| Markwick Holdings Group Ltd | Financial services | 2025 |
| Markwick Property Holdings Ltd | Real estate | 2025 |
| Marle Piece Properties Limited | Real estate | 2017 |
| Mars Property Ventures Ltd | Real estate | 2024 |
| Marschelle Limited | Extraterritorial | 2015 |
| Marshfield Monkeys Day Nursery Wrap Around & Holiday Club Ltd | Health & social care | 2021 |
| Marstol Limited | Health & social care | 2024 |
| Martels Wholesalers Limited | Wholesale & retail | 2017 |
| Martin John Evans Associates Ltd | Professional & scientific | 2020 |
| Martinsmaterial Ltd | Wholesale & retail | 2025 |
| Martyn Prowel Property Limited | Real estate | 2022 |
| Martyn Reader Mortgages Limited | Financial services | 2017 |