| Marquis Insurance Brokers Limited | Financial services | 2014 |
| Marr Contracting (International) Ltd | Construction | 2016 |
| Marra Industries Ltd | Administrative & support | 2022 |
| Marrion Wealth Management Limited | Financial services | 2024 |
| Marriot Limited | Wholesale & retail | 2025 |
| Marriott Financial Consulting Ltd | Professional & scientific | 2020 |
| Marroccofellas Limited | Real estate | 2003 |
| Mars Consulting Ltd | Information & communication | 2026 |
| MARS17 Ltd | Transport & logistics | 2024 |
| Marsay Reselling Ltd | Wholesale & retail | 2023 |
| Marsden Cloud Ltd | Information & communication | 2023 |
| Marsden Court Management Company Limited | Households | 1984 |
| Marsden Educational Psychology Ltd | Education | 2025 |
| Marsel Display Company Limited | Manufacturing | 1976 |
| Marsh Corporate Compliance Limited | Information & communication | 2015 |
| Marsh Corporate Consulting Limited | Professional & scientific | 1990 |
| Marsh Lane Apartments Limited | Real estate | 2007 |
| Marsh Recruitment Ltd | Administrative & support | 2024 |
| Marshall & Co (2000) Limited | Administrative & support | 2010 |
| Marshall Bradbury Properties Ltd | Real estate | 2022 |
| Marshall Capital Limited | Financial services | 2025 |
| Marshall Carter Limited | Information & communication | 2011 |
| Marshall Court Management Company Limited | Households | 2002 |
| Marshall Electrical (Yorkshire) Ltd | Construction | 2026 |
| Marshall Farmer Limited | Wholesale & retail | 1976 |
| Marshall Jones Ltd | Construction | 2017 |
| Marshall Made Limited | Information & communication | 2012 |
| Marshall Property Developments Limited | Real estate | 2015 |
| Marshall Search Limited | Administrative & support | 2003 |
| Marshall Studios Ltd | Professional & scientific | 2020 |
| Marshall Thompson Leadwork Limited | Construction | 2021 |
| Marshall Wealth Management Limited | Financial services | 2014 |
| Marshall Wooldridge Financial Services Limited | Financial services | 2015 |
| Marshall Wooldridge Wealth Management Ltd | Financial services | 2021 |
| Marshallprint Limited | Manufacturing | 2009 |
| Marshalls Dormant (NO.1) Limited | Professional & scientific | 1922 |
| Marshalls Dormant (NO.6) Limited | Professional & scientific | 1904 |
| Marshalls Dormant (NO.9) Limited | Professional & scientific | 1924 |
| Marshalls Equine Ltd | Agriculture & fishing | 2025 |
| Marshalls Property Group Ltd | Real estate | 2022 |
| Marshall’S Renovations Limited | Construction | 2021 |
| Marsham Properties Limited | Construction | 2007 |
| Marshgate Properties Limited | Real estate | 2000 |
| Marshk Engg Ltd | Professional & scientific | 2019 |
| Marsley Forwarding Limited | Transport & logistics | 1981 |
| Marster Manufactories Ltd | Manufacturing | 2025 |
| Martatransport Ltd | Transport & logistics | 2025 |
| Martello Civil Infrastructure Ltd | Construction | 2025 |
| Martha's Creation Station Ltd | Arts & recreation | 2025 |
| Marthon Limited | | 1969 |
| Martial Limited | Real estate | 2019 |
| Martial Marketing Limited | Professional & scientific | 2024 |
| Martin Day Electricians Limited | Construction | 2009 |
| Martin Dresner Limited | Health & social care | 2011 |
| Martin Flynn Sport Limited | Professional & scientific | 2013 |
| Martin Gaffney Legal Services Limited | Professional & scientific | 2009 |
| Martin Hirst Holdings Limited | Financial services | 2005 |
| Martin Lloyds Ltd | Administrative & support | 2024 |
| Martin MAE Interiors Limited | Wholesale & retail | 2024 |
| Martin Mullen Building Contractors Limited | Construction | 2008 |
| Martin Pears Sporting Limited | Agriculture & fishing | 2018 |
| Martin ST Development Ltd | Construction | 2018 |
| Martin Thornton Lettings Ltd | Real estate | 2017 |
| Martin Thornton Ltd | Real estate | 2015 |
| Martina Rocha LUZ Ltd | Arts & recreation | 2022 |
| Martindale Analytical Services Limited | Transport & logistics | 2016 |
| Martindale Group Holdings Limited | Professional & scientific | 2019 |
| Martindale Group Limited | Professional & scientific | 2015 |
| Martindale Leasing Limited | Administrative & support | 2023 |
| Martindale Property Management Limited | Real estate | 2016 |
| Martinhal (Gym 2024) Limited | Arts & recreation | 2024 |
| Martinhal LLP | | 2005 |
| Martinhal Properties Limited | Construction | 2018 |
| Martini Engineering Limited | Professional & scientific | 2005 |
| Martini Private Ltd | Financial services | 2018 |
| Martins Travel and Transport Ltd | Transport & logistics | 2025 |
| Martinville Developments Limited | Extraterritorial | 2021 |
| Martius Limited | | 1983 |
| Marton Road (Bridlington) Management Company Limited | Real estate | 2005 |
| Martyn Carnell Property Ltd | Real estate | 2021 |
| Marufi Merchants Limited | Wholesale & retail | 2025 |
| Marun Care Ltd | Health & social care | 2026 |
| Maruti Ltd | Wholesale & retail | 2026 |
| Marvel Accountants (UK) Ltd | Professional & scientific | 2023 |
| Marvel Commercial Ltd | Professional & scientific | 2021 |
| Marvel Financial Group Ltd | Extraterritorial | 2021 |
| Marvel Financial Ltd | Financial services | 2019 |
| Marvel Qualities Limited | Information & communication | 2017 |
| Marvica Cleaning Services Ltd | Administrative & support | 2023 |
| Marvin Medical Limited | Administrative & support | 2022 |
| Marweezy Ltd | Real estate | 2023 |
| Marweezy Real Estate Ltd | Real estate | 2024 |
| Marwood Flooring Company Limited | Professional & scientific | 1976 |
| Mary & K Cleaning Service Ltd | Administrative & support | 2025 |
| Mary & MAI Events Ltd | Administrative & support | 2024 |
| Mary Catherine Ynot Ltd | Health & social care | 2025 |
| Mary Claire Limited | Other services | 2019 |
| Mary Deering Catering Limited | Hospitality | 2018 |
| Mary Randall Vickers & Co Limited | Manufacturing | 2017 |
| Mary Seacole Nurses Association | Health & social care | 1989 |