| Marwan Faqee Deliveries Ltd | Transport & logistics | 2025 |
| Marwin & Partners | | 1991 |
| Marwyn Capital Growth GP Limited | Administrative & support | 2010 |
| Marwyn Capital Growth LP | | 2010 |
| Mary Carslaw Architects Limited | Professional & scientific | 2021 |
| Mary Teresa Deeney Limited | Extraterritorial | 2025 |
| Mary Teresa Walker Limited | Extraterritorial | 2025 |
| Mary's Cleaning Ltd | Administrative & support | 2023 |
| Mary's Milk Bar Ltd | Hospitality | 2015 |
| Maryan Lake SP | | 2004 |
| Marybond Group LP | | 2017 |
| Marynsol Limited | Information & communication | 2016 |
| Maryon Investments LP | | 2013 |
| Maryport Management LP | | 2013 |
| Maryport Trading LP | | 2010 |
| Marysia Software Limited | Manufacturing | 2019 |
| Marytree Associates LP | | 2010 |
| Marzella Estates Ltd | Real estate | 2019 |
| Masala Leaves Limited | Hospitality | 2024 |
| Masala Wheels Limited | Hospitality | 2025 |
| Masamo Business LP | | 2020 |
| Masaq Software Ltd | Information & communication | 2026 |
| Masawa LP | | 2002 |
| Mascot Group Limited | Professional & scientific | 2015 |
| Masfida Conception LP | | 2017 |
| Mash TUN Edinburgh Ltd | Hospitality | 2026 |
| Mask Logic Ltd | Manufacturing | 2021 |
| Maskell SLP | | 1998 |
| Masnyk Engineering Ltd | Professional & scientific | 2023 |
| Mason & Carr Property Management Ltd | Households | 2022 |
| Mason Bathroom Designs Ltd | Construction | 2025 |
| Mason Bone Projects Limited | Arts & recreation | 2014 |
| Mason Lumiere Properties Ltd | Real estate | 2025 |
| Mason Trade LP | | 2013 |
| Mason Trading LP | | 2017 |
| Masonhill Lease Holdings Ltd | Real estate | 2024 |
| Masonry Heater Builders Ltd | Construction | 2012 |
| Masons Arms Public House Limited | Hospitality | 2025 |
| Maspero Consulting Limited | Professional & scientific | 2012 |
| Masqua Holding LP | | 2016 |
| Mass Barber Shop Ltd | Other services | 2023 |
| Massevar Ltd | Administrative & support | 2023 |
| Massilyas Ecom LP | | 2020 |
| Massimiliano Ercolini LP | | 2018 |
| Massiva Services LP | | 2015 |
| Massive Associates (UK) Ltd. | Professional & scientific | 2018 |
| Massive Star LP | | 2016 |
| Masson Watson Beauty Ltd | Other services | 2024 |
| Masson Watson Holdings Ltd | Real estate | 2024 |
| Mastak Ltd | Wholesale & retail | 2025 |
| Mastar Trade LP | | 2017 |
| Maste Overseas L.P. | | 2011 |
| Master Approach LP | | 2016 |
| Master Business Services L.P. | | 2012 |
| Master Corporation L.P. | | 2012 |
| Master CUT Barberz Ltd | Other services | 2024 |
| Master Data Marvel Ltd | Information & communication | 2023 |
| Master Enterprises L.P. | | 2014 |
| Master Express L.P. | | 2011 |
| Master Genta LP | | 2015 |
| Master Global Services L.P. | | 2012 |
| Master Imports/Exports L.P. | | 2011 |
| Master Industrial Services L.P. | | 2011 |
| Master International Investments LP | | 2009 |
| Master IT Solutions Ltd | Information & communication | 2012 |
| Master Logistics Trade LP | | 2016 |
| Master Networks L.P. | | 2009 |
| Master of Code LP | | 2012 |
| Master Sincere Investment LP | | 2016 |
| Master Steel and Commodities LP | | 2017 |
| Master Supplier Pro Limited | Wholesale & retail | 2025 |
| Master Tailoring Ltd | Other services | 2020 |
| Master Touches Ltd | Real estate | 2022 |
| Master Trade Alliance LP | | 2015 |
| Master Wholesale L.P. | | 2012 |
| Master Window Cleaners Ltd | Administrative & support | 2003 |
| Master-Peace Recruitment Ltd | Administrative & support | 2010 |
| Mastercorp Investments L.P. | | 2012 |
| Mastercraft Joinery & Carpentry Ltd | Construction | 2024 |
| Masterfield Investments L.P. | | 2009 |
| Masterman Hall Ltd | Professional & scientific | 2025 |
| Masterplan Business and Engineering Limited | Professional & scientific | 2014 |
| Masterplan Developments L.P. | | 2011 |
| Masters & Steel LP | | 2016 |
| Masters Enviro Ltd | Professional & scientific | 2025 |
| Masters Trade LP | | 2017 |
| Masterserv Property Maintenance Ltd | Construction | 2025 |
| Mastertech Europe L.P. | | 2010 |
| Mastertech International L.P. | | 2008 |
| Masterton Impex LP | | 2016 |
| Masterton Properties Ltd | Real estate | 2024 |
| Mastertrade Group LP | | 2016 |
| Mastertrans LP | | 2011 |
| Mastex Group L.P. | | 2009 |
| Mastex LP | | 2015 |
| Masthouse Associates Ltd | Professional & scientific | 2025 |
| Masti Dundee Terrace Limited | Hospitality | 2024 |
| Masti Edinburgh Limited | Hospitality | 2021 |
| Masutes Group Limited | Financial services | 2017 |
| Matador LP General Partner Limited | Administrative & support | 2005 |