| Maradolf International Limited | Administrative & support | 2021 |
| Maradolf Properties Acquisition and Management Limited | Real estate | 2021 |
| Mararep Ltd | Financial services | 2024 |
| Marbas Consulting Ltd | Construction | 2022 |
| Marbas Frost Solutions Limited | Construction | 2023 |
| Marbelia-Lux Ltd | Construction | 2025 |
| Marble House W9 Ltd | Real estate | 2023 |
| Marble Star Ltd | Construction | 2018 |
| Marbleous Limited | Wholesale & retail | 2009 |
| Marcel Marketing Ltd | Other services | 2019 |
| Marcel Mechanical Limited | Construction | 2024 |
| Marcel Services 73 Ltd | Transport & logistics | 2015 |
| Marchaa Foods Limited | Manufacturing | 2021 |
| Marci Polish Ltd | Other services | 2025 |
| Marcomedia Solutions (London) Ltd | Professional & scientific | 2010 |
| Marcon Works Limited | Construction | 2023 |
| Marconi Shaving Limited | Wholesale & retail | 2018 |
| Marcroft PLC | | 1989 |
| Marcsom Limited | Construction | 2018 |
| Mardari Pro FIX Ltd | Construction | 2024 |
| Mardass Ltd | Other services | 2019 |
| Marengo 1 Limited | Real estate | 2019 |
| Marentin Solutions Limited | Construction | 2026 |
| Marep Ltd | Wholesale & retail | 2021 |
| Margaret Rudo Ltd | Health & social care | 2018 |
| Margaret Way Management Company Limited | Real estate | 1979 |
| Margate Pump House Limited | Real estate | 2017 |
| Margery Park Road Ltd | Real estate | 2015 |
| Margjoka Construction Ltd | Construction | 2024 |
| Marhaba Recovery Ltd | Transport & logistics | 2020 |
| Marhal Ltd | Real estate | 2022 |
| Maria Beauty Limited | Other services | 2013 |
| Maria Cosmetics Ltd | Wholesale & retail | 2025 |
| Maria Faisal Ltd | Wholesale & retail | 2025 |
| Maria GRD Limited | Wholesale & retail | 2020 |
| Maria Jbee Ltd | Wholesale & retail | 2023 |
| Marian Iliuta Ltd | Construction | 2020 |
| Mariana Radu Limited | Transport & logistics | 2025 |
| Mariana's World Ltd | Transport & logistics | 2024 |
| Marical Ltd | Real estate | 2024 |
| Maridana Ltd | Construction | 2026 |
| Marijan FI LLP | | 2017 |
| Marikar Investments Ltd | Real estate | 2020 |
| Marimirva Trans Ltd | Transport & logistics | 2022 |
| Marinou Psychotherapy Ltd | Health & social care | 2024 |
| Mario&George Construction Ltd | Construction | 2020 |
| Mariocom Limited | Transport & logistics | 2013 |
| Maristella Ltd | Manufacturing | 2023 |
| Mariton Ltd | Administrative & support | 2018 |
| Marius Colors Ltd | Construction | 2025 |
| Marius Decoration Ltd | Construction | 2019 |
| Marius Marian Gheorghe Ltd | Construction | 2025 |
| Marius Painting Services Ltd | Construction | 2014 |
| Mariwo Care Services Limited | Health & social care | 2024 |
| Mark & Mario Cleaning Service Limited | Administrative & support | 2025 |
| Mark & Sons Limited | Hospitality | 2006 |
| Mark Dawson & SON Ltd | Construction | 2015 |
| Mark Dennis Chauffeurs Limited | Transport & logistics | 2024 |
| Mark Higgins Property Limited | Real estate | 2006 |
| Mark Howell (Trade) Limited | Wholesale & retail | 2023 |
| Mark Howell Limited | Wholesale & retail | 2020 |
| Mark One Creative Limited | Information & communication | 2011 |
| Marker Investments Limited | Real estate | 2020 |
| Marker Master Limited | Real estate | 2025 |
| Market B&B Limited | Wholesale & retail | 2025 |
| Market Research for YOU (London) Ltd | Professional & scientific | 2016 |
| Market Zone Limited | Wholesale & retail | 2024 |
| Markethaven Commerce Ltd | Wholesale & retail | 2026 |
| Marketing Expert UK Limited | Professional & scientific | 2021 |
| Marketingprouk Ltd | Wholesale & retail | 2019 |
| Marketlywork Limited | Information & communication | 2025 |
| Marketmate Limited | Wholesale & retail | 2025 |
| Markhor Airlines Ltd | Transport & logistics | 2026 |
| Markhor Capital Ltd | Real estate | 2021 |
| Markhor Cricket Club Ltd | Arts & recreation | 2024 |
| Markhor Investments Ltd | Real estate | 2021 |
| Markitizer Limited | Professional & scientific | 2021 |
| Markkit Ltd | Wholesale & retail | 2026 |
| Marklay Estates Ltd | Real estate | 2018 |
| Marklay Mortgages Ltd | Financial services | 2019 |
| Marks Haulage Limited | Wholesale & retail | 2018 |
| Marland Property Services Ltd | Real estate | 2018 |
| Marlands Investments Limited | Real estate | 2011 |
| Marlborough House Holdings Ltd | Real estate | 2026 |
| Marlborough Street Construction Limited | Construction | 1998 |
| Marlborough Street Properties Limited | Real estate | 1988 |
| Marlborough Street Property Holdings Ltd | Financial services | 2021 |
| Marlborought Enterprises Limited | Information & communication | 2023 |
| Marlin Soft Technologies Ltd | Information & communication | 2024 |
| Marlow Autos Ltd | Wholesale & retail | 2022 |
| Marmalade Property Solutions Limited | Real estate | 2019 |
| Marmar Construction Limited | Construction | 2025 |
| Marns Properties Ltd | Real estate | 2019 |
| Maroof & SON Ltd | Real estate | 2022 |
| Marquees U K Limited | Professional & scientific | 2009 |
| Marquis IT Ltd | Professional & scientific | 2010 |
| Marr Traders Ltd | Wholesale & retail | 2021 |
| Marrany Ltd | Construction | 2018 |
| Marrygate Ltd | Information & communication | 2025 |
| Mars International Ltd | Wholesale & retail | 2025 |