| Mark Brands Group Ltd | Wholesale & retail | 2024 |
| Mark Kelly Trading Company Ltd | Professional & scientific | 2018 |
| Mark Tester Limited | Wholesale & retail | 2015 |
| Markdasilva Ltd | Real estate | 2025 |
| Marketing Sciences 4U Ltd | Professional & scientific | 2023 |
| Marketron Digital Solutions Limited | Professional & scientific | 2026 |
| Marketshare Initiatives Limited | Information & communication | 2020 |
| Markhor Realty Ltd | Administrative & support | 2023 |
| Markpapp.Tv Limited | Information & communication | 2014 |
| Marks and Marks Limited | Wholesale & retail | 2020 |
| Marley Strategy Ltd | Professional & scientific | 2024 |
| Marmont Management Ltd | Other services | 1983 |
| Marsdens Caterers of Sheffield Limited | Hospitality | 1939 |
| Marshland Limited | Information & communication | 2004 |
| Marsworth House Management Company Limited | Extraterritorial | 2014 |
| Martial World Limited | Arts & recreation | 2020 |
| Martin Polke Limited | Construction | 2012 |
| Martinax Property Solutions Ltd | Construction | 2026 |
| Martini Film Productions Ltd | Information & communication | 2025 |
| Martins Greengrocers & Florist Limited | Wholesale & retail | 2010 |
| Maru Creates Ltd | Construction | 2021 |
| Marutham Ltd | Professional & scientific | 2023 |
| Maruthi Express Limited | Hospitality | 2025 |
| Maruti Aircon Ltd | Manufacturing | 2025 |
| Maruti Arrk Ltd | Real estate | 2018 |
| Marvel Building Solutions Ltd | Construction | 2020 |
| Marvel Home Properties Ltd | Real estate | 2024 |
| Marvellous Creator Limited | Administrative & support | 2023 |
| Marvellous Hair and Beauty Parlour Limited | Other services | 2026 |
| Marvellous International Ltd. | Administrative & support | 2016 |
| Marvra Limited | Construction | 2020 |
| Marwan Auto Ltd | Wholesale & retail | 2020 |
| Maryam Jewellers Limited | Wholesale & retail | 2026 |
| Maryam’S Gift Box Ltd | Wholesale & retail | 2026 |
| Marycos Limited | Transport & logistics | 2016 |
| Marylebone Holdco Limited | Transport & logistics | 2019 |
| Marz Limited | Professional & scientific | 2005 |
| MAS Cargo Company Ltd | Transport & logistics | 2026 |
| MAS Meta Limited | Education | 2021 |
| Masala London Limited | Real estate | 2019 |
| Masc Holdings Ltd | Financial services | 2021 |
| Mascar Services Ltd | Administrative & support | 2024 |
| Masco (GB) Limited | Wholesale & retail | 2014 |
| Masg Ltd | Construction | 2025 |
| Masguitarra Ltd | Wholesale & retail | 2018 |
| Mashhad Bilal Hajj & Umrah Services Ltd | Administrative & support | 2025 |
| Masor Construction Ltd | Construction | 2025 |
| Mass Beautician Ltd | Other services | 2014 |
| Mass Cooling Ltd | Energy | 2023 |
| Massage Mama Limited | Other services | 2023 |
| Master Finance Limited | Professional & scientific | 2014 |
| Master Vendor 1 Ltd | Wholesale & retail | 2021 |
| Master Wholesaler Ltd | Manufacturing | 2022 |
| Masterclass-Cricket-Academy Ltd | Arts & recreation | 2017 |
| Masterclass-Cricket-Coaching Ltd | Arts & recreation | 2023 |
| Mastermind Design & Build Limited | Construction | 2023 |
| Masti Enterprises Ltd | Hospitality | 2019 |
| Masti London Ltd | Hospitality | 2019 |
| Mastron Ltd | Wholesale & retail | 2020 |
| Matagrafix IT Solution Ltd | Information & communication | 2025 |
| Matbakh AL Khaleej AL Arabi Ltd | Hospitality | 2014 |
| Match Cosmetics Limited | Other services | 2026 |
| Matden Ltd | Construction | 2018 |
| Matel Limited | Extraterritorial | 2022 |
| Math Mentor London Limited | Education | 2024 |
| Mathuman Invest Ltd | Real estate | 2017 |
| Matishalin Consultants Ltd | Professional & scientific | 2014 |
| Matplus Consulting Ltd. | Professional & scientific | 2017 |
| Matplus Leasehold Limited | Real estate | 2025 |
| Matplus Limited | Professional & scientific | 2014 |
| Matplus Properties Limited | Administrative & support | 2009 |
| Matplus Property Holding Ltd | Real estate | 2020 |
| Matplus Wills & Probate Ltd | Professional & scientific | 2012 |
| Matrix Anna Ltd | Health & social care | 2010 |
| Matrix Glass Ltd | Manufacturing | 2024 |
| Matrix Transport Logistics Limited | Transport & logistics | 2020 |
| Matsumoto Limited | Information & communication | 2024 |
| Matt Stuart Limited | Professional & scientific | 2006 |
| Mattos Films Limited | Information & communication | 2023 |
| Matuszak Implantology Limited | Health & social care | 2017 |
| Matv Broadcasting Limited | Information & communication | 2008 |
| MAU Formwork Ltd | Construction | 2016 |
| Maveric Impex Ltd | Construction | 2008 |
| MAX 7P Limited | Information & communication | 2016 |
| MAX Food Distributors Ltd | Wholesale & retail | 2022 |
| MAX Joiners Ltd | Construction | 2019 |
| MAX Medical Products Ltd | Manufacturing | 2010 |
| MAX Power Nutrition Ltd | Hospitality | 2022 |
| Maxhair Limited | Other services | 2006 |
| Maxi Autos Ltd | Wholesale & retail | 2021 |
| Maxima Logic Ltd | Wholesale & retail | 2025 |
| Maximum Care Excellence Ltd | Health & social care | 2025 |
| Maximus Legal Limited | Professional & scientific | 2020 |
| Maxlond Ltd. | Construction | 2015 |
| Maxou Traders Ltd | Construction | 2011 |
| Maxxvending Ltd | Wholesale & retail | 2025 |
| MAY Properties U.K. Limited | Real estate | 2017 |
| Maya Hotel Ltd | Hospitality | 2015 |
| Mayaa Limited | Transport & logistics | 2022 |
| Mayfair & Co Chauffers Ltd | Transport & logistics | 2025 |