| Marinestead Limited | Extraterritorial | 2013 |
| Mario 95 Ltd | Transport & logistics | 2022 |
| Marioalexandru Ltd | Transport & logistics | 2017 |
| Mariosab Ltd | Transport & logistics | 2019 |
| Mariot Limited | Transport & logistics | 2018 |
| Maris Family Properties Ltd | Construction | 2022 |
| Maris Properties Investments Ltd | Real estate | 2026 |
| Maris Way Management Company Limited | Real estate | 2024 |
| Marist Beheer Ltd | Extraterritorial | 2012 |
| Maristella Property Limited | Real estate | 2019 |
| Marius Dany Trans Ltd | Transport & logistics | 2018 |
| Marius Mihaescu Ltd | Transport & logistics | 2025 |
| Marj & Retas (Preston) Limited | Hospitality | 2026 |
| Marj 27 Property Ltd | Real estate | 2025 |
| Mark Appleyard Limited | Administrative & support | 2007 |
| Mark Dickinson Limited | Financial services | 2025 |
| Mark Eduard Mocanu Ltd | Transport & logistics | 2022 |
| Mark Fairclough Electrical Limited | Manufacturing | 1997 |
| Mark Fisher (Legal Services) Limited | Professional & scientific | 2022 |
| Mark Herczeg Ltd | Professional & scientific | 2024 |
| Mark Kelly Consultancy Ltd | Information & communication | 2025 |
| Mark Pashley Limited | Manufacturing | 2008 |
| Mark Radford Design Limited | Professional & scientific | 2021 |
| Mark Sellars Construction 2017 Limited | Construction | 2017 |
| Mark Stretton Flooring Services Ltd | Construction | 2017 |
| Markannelouise Ltd | Hospitality | 2026 |
| Market CAF Ltd | Hospitality | 2024 |
| Market Place Bawtry Ltd | Construction | 2023 |
| Market Place Residential Limited | Real estate | 2023 |
| Marketing & Professional Management Ltd | Wholesale & retail | 2015 |
| Marketnet Ltd | Wholesale & retail | 2025 |
| Markl Ltd | Transport & logistics | 2024 |
| Markpoint Restaurant Group Limited | Financial services | 2025 |
| Markshif Limited | Information & communication | 2026 |
| Marlew LLP | | 2024 |
| Marley Construction Limited | Construction | 2018 |
| Marley Plant Limited | Administrative & support | 2023 |
| Marlong Ltd | Transport & logistics | 2025 |
| Marlow Assets Limited | Financial services | 2025 |
| Marlowe Anodising Limited | Manufacturing | 2025 |
| Marlowe United Limited | Extraterritorial | 2026 |
| Marlroy Property Limited | Real estate | 2025 |
| Marltec Limited | Manufacturing | 2025 |
| Marmalade Forge Ltd | Extraterritorial | 2026 |
| Maroga Bogdan Ltd | Transport & logistics | 2019 |
| Marpaul Properties Limited | Real estate | 2003 |
| Marr Grange Farm Limited | Agriculture & fishing | 2012 |
| Marrico (Sovereign Square) Ltd | Construction | 2019 |
| Marrico Asset Management LLP | | 2013 |
| Marriott Property Portfolio Limited | Real estate | 2007 |
| Marrth Limited | Construction | 2023 |
| Marsden Car & Commercial Limited | Wholesale & retail | 2024 |
| Marsden City Developments Ltd | Construction | 2024 |
| Marsden Electrical Limited | Manufacturing | 2015 |
| Marsha Meredith Ltd | Professional & scientific | 2020 |
| Marshall Farming Limited | Agriculture & fishing | 2004 |
| Marshall Property Networks Ltd | Real estate | 2024 |
| Marshall Property Purchasing Ltd | Real estate | 2026 |
| Marshall's Landscaping Limited | Administrative & support | 2016 |
| Marshall's Property Holdings Limited | Real estate | 2019 |
| Marshalls Butchers Limited | Wholesale & retail | 2018 |
| Marshalls Deli & Rotisserie Limited | Wholesale & retail | 2022 |
| Marshgate Medical Locums Limited | Health & social care | 2010 |
| Marshgate Medical Services Limited | Health & social care | 2011 |
| Marsman Group Ltd | Construction | 2026 |
| Marss Investments (UK) Ltd | Construction | 2023 |
| Martec Cooling Ltd | Construction | 2026 |
| Martek Ventures Ltd | Financial services | 2026 |
| Martial Arts 4 U Doncaster Ltd | Education | 2025 |
| Martial Arts Masters Organisation Ltd | Arts & recreation | 2024 |
| Martin & Co Building Contractors Limited | Construction | 2016 |
| Martin Little Memorial Services Limited | Manufacturing | 2003 |
| Martin Roberts Draughtsman Ltd | Administrative & support | 2017 |
| Martin Sprint Car Limited | Transport & logistics | 2022 |
| Martin Walker Consulting Limited | Professional & scientific | 2015 |
| Martines Cars Ltd | Wholesale & retail | 2017 |
| Martiz Associates Ltd | Education | 2014 |
| Martland Park Holdings Limited | Financial services | 2022 |
| Martland Park Investments Limited | Other services | 2025 |
| Martlet Geoscience Ltd | Professional & scientific | 2023 |
| Martyn J Durant Management Services Limited | Professional & scientific | 2016 |
| Maru Commercial Ltd | Transport & logistics | 2019 |
| Marv Restaurant Ltd | Hospitality | 2025 |
| Marvel Glam Limited | Wholesale & retail | 2025 |
| Marvel Heating & Renewable Energy Ltd | Construction | 2018 |
| Marwah Medics Ltd | Professional & scientific | 2026 |
| Marwood Associates Ltd | Administrative & support | 2023 |
| Mary Cargo Trans Ltd | Transport & logistics | 2019 |
| Marylebone School of English Limited | Extraterritorial | 2022 |
| Maryo & Tony Ltd | Transport & logistics | 2021 |
| MAS Construction & Maintenance Ltd | Construction | 2011 |
| Masal Pizza Limited | Hospitality | 2020 |
| Masala Bentley Doncaster Ltd | Hospitality | 2023 |
| Masalar Transport Ltd | Transport & logistics | 2022 |
| Masda Homes Ltd | Real estate | 2022 |
| Masefield Building Services Limited | Construction | 2011 |
| Maseli Limited | Health & social care | 2016 |
| Mason Electrical Services Limited | Construction | 2007 |
| Mason Manor Properties Ltd | Real estate | 2020 |
| Mason Site Safety Ltd | Construction | 2024 |