| March Newspapers Limited | Wholesale & retail | 2002 |
| Marchburn Properties Limited | Real estate | 2024 |
| Marchmont Assets Ltd | Real estate | 2017 |
| Marchmont Capital Ltd | Real estate | 2017 |
| Marcus Alderson Developments Limited | Construction | 2023 |
| Marcus Alderson Estate Agents Limited | Real estate | 2006 |
| Marcus Alderson Hips Limited | Real estate | 2008 |
| Margot Walker Ltd | Extraterritorial | 2017 |
| Maria Ferguson Planning Limited | Professional & scientific | 2014 |
| Marie Larby Accountancy Ltd | Professional & scientific | 2012 |
| Marista Global Limited | Wholesale & retail | 2023 |
| Mark Andrew Search Limited | Administrative & support | 2024 |
| Mark Edmunds Marketing Services Limited | Professional & scientific | 2016 |
| Mark Goldstein Associates Ltd | Other services | 2012 |
| Mark Macnab Limited | Construction | 2024 |
| Mark Scott Enterprises Limited | Administrative & support | 2003 |
| Market Place Lettings Limited | Hospitality | 2026 |
| Marketconsult Ltd | Professional & scientific | 2009 |
| Marksbury Developments Limited | Professional & scientific | 2022 |
| Marktechfusion Limited | Wholesale & retail | 2024 |
| Markview International Consultancy Limited | Administrative & support | 1996 |
| Marlborough Advisors Limited | Administrative & support | 2010 |
| Marlin Intelligence Limited | Professional & scientific | 2026 |
| Marrelle International Ltd | Education | 2021 |
| Marrick Lodge Farm Ltd | Agriculture & fishing | 2025 |
| Marrick Priory Trust | Education | 2000 |
| Marriott Consulting Ltd | Professional & scientific | 2025 |
| Marsh END Management Company Limited | Households | 2006 |
| Marske Hall Leased Estate Ltd | Real estate | 2025 |
| Marston Park Ltd | Hospitality | 2016 |
| Martin Campbell and Company Limited | Real estate | 2011 |
| Martin Clark Plumbing and Heating Limited | Construction | 2018 |
| Martin Family Investment Company Limited | Professional & scientific | 2017 |
| Martin Parker Consulting Ltd | Professional & scientific | 2010 |
| Martin Rafferty Gardens Limited | Administrative & support | 2014 |
| Martineau TW1 Ltd | Real estate | 2020 |
| Martone Proerty Management Limited | | 2023 |
| Marzamemi Ltd | Hospitality | 2023 |
| Mascol Technologies Ltd | Manufacturing | 2020 |
| MASH3 Limited | Information & communication | 2008 |
| Mason Chiropractic Clinic Limited | Health & social care | 2007 |
| Mason Woodchippers Limited | Manufacturing | 2016 |
| Mast International Learning and Development Limited | Administrative & support | 2018 |
| Mastercar Limited | Wholesale & retail | 1994 |
| Masterclass Investments Limited | Professional & scientific | 2017 |
| Masterclass Resourcing Limited | Administrative & support | 2008 |
| Matalogue UK Limited | Professional & scientific | 2025 |
| Match Star Ltd | Arts & recreation | 2026 |
| Matchday Pets Ltd | Wholesale & retail | 2026 |
| Matt Ball Architecture LLP | | 2017 |
| Matt Films Ltd | Administrative & support | 2025 |
| Matt Williams Management Limited | Professional & scientific | 2018 |
| Matter of Management Ltd | Real estate | 2003 |
| Matty Cole Property Investments Ltd | Real estate | 2025 |
| Matwest (GDI) Ltd | Construction | 2015 |
| Matwest Ltd | Real estate | 2006 |
| Maudes Developments Ltd | Construction | 2026 |
| Maudes Holdings Ltd | Professional & scientific | 2026 |
| Maudes Plumbing & Heating Ltd | Construction | 2026 |
| Mawer Truck & Plant Ltd | Wholesale & retail | 2021 |
| MAX Coates Motorsports and Marketing Ltd | Information & communication | 2017 |
| Maxwell Public Relations Limited | Professional & scientific | 2019 |
| Mayfair Health Consultancy Limited | Health & social care | 2017 |
| Mayfair Risk Solutions Limited | Financial services | 2026 |
| Mayfields Rentals Limited | Hospitality | 2002 |
| MBD Education Services Limited | Administrative & support | 2010 |
| MBD House Ltd | Manufacturing | 1984 |
| MBM Travel Executives Limited | Administrative & support | 2014 |
| Mbna Services Ltd | Professional & scientific | 2024 |
| MBS Accounting Ltd | Professional & scientific | 2015 |
| Mcda Ltd. | Professional & scientific | 2018 |
| Mcewan Travel Associates Limited | Administrative & support | 2014 |
| Mclean Technology Ltd | Information & communication | 2021 |
| Mcluckie Projects Limited | Real estate | 1996 |
| Mcmahons Point Capital Limited | Professional & scientific | 2013 |
| Mcpi Rentals Ltd | Real estate | 2026 |
| MCS Pro Limited | Extraterritorial | 2018 |
| Mctaggart-Scott Ltd | Administrative & support | 2005 |
| MD9 Ltd | Education | 2025 |
| MDI Consultancy Limited | Professional & scientific | 2012 |
| Mdsa Services Limited | Professional & scientific | 2016 |
| Meadowgate Clinical Services Ltd | Health & social care | 2024 |
| Meat Advisory Limited | Wholesale & retail | 2026 |
| Mebeidcreations Ltd | Information & communication | 2018 |
| Mechanised Talent Limited | Professional & scientific | 2016 |
| Media Dreams Limited | Information & communication | 2008 |
| Medianature Consultancy UK Ltd | Professional & scientific | 2020 |
| Medicine Head Ltd | Wholesale & retail | 2022 |
| Medieval Music in the Dales Community Interest Company | Arts & recreation | 2025 |
| Medipro Consulting Limited | Professional & scientific | 2010 |
| Medius Resources Ltd | Other services | 2019 |
| Medscicommsnet Limited | Professional & scientific | 2025 |
| Meetings of Minds Limited | Administrative & support | 2004 |
| Mega Grid Limited | Professional & scientific | 2024 |
| Melbourne Street Properties Limited | Real estate | 1918 |
| Melon Worzel Limited | Other services | 2002 |
| Melrose Financial Limited | Administrative & support | 2016 |
| Melsonby Property Management Limited | Real estate | 2008 |
| Melt Content Limited | Professional & scientific | 2013 |
| Melville Advisors Limited | Professional & scientific | 2017 |