| Markiz Property Ltd | Real estate | 2023 |
| Markiz UK Limited | Wholesale & retail | 2016 |
| Markoulias Group Holdings Limited | Financial services | 2025 |
| Marku Holdings Ltd | Real estate | 2026 |
| Markus Pro Ltd | Wholesale & retail | 2021 |
| Marle Electrical Solutions Ltd | Extraterritorial | 2014 |
| Marlo's Barbers Ltd | Other services | 2025 |
| Marlon United Shipping & Trading UK Limited | Transport & logistics | 2017 |
| Marlow Construction Limited | Construction | 2012 |
| Marmara Maya Ltd | Wholesale & retail | 2018 |
| Marneale Ltd | Education | 2026 |
| Maroonwise Limited | Real estate | 2026 |
| Marsbarspars Limited | Information & communication | 2026 |
| Marsh & Partners Limited | Professional & scientific | 2018 |
| Marshall Roofing and Building Ltd | Construction | 2025 |
| Marshmallow London Limited | Professional & scientific | 2016 |
| Martin Mcmanus Services Ltd | Health & social care | 2026 |
| Martin Surveying Associates Limited | Real estate | 2014 |
| Maryanconstruction Ltd | Construction | 2024 |
| Marylinx Ltd | Wholesale & retail | 2024 |
| Maryo & Nickol Limited | Hospitality | 2025 |
| Masadi Limited | Transport & logistics | 2016 |
| Masalski Services Ltd | Construction | 2022 |
| Mascot Legal Ltd | Professional & scientific | 2019 |
| Masih Properties London Ltd | Real estate | 2022 |
| Masom Landscape Architecture Ltd | Real estate | 2020 |
| Mason Stone Ltd | Wholesale & retail | 2025 |
| Masons Capital Ltd | Real estate | 2024 |
| Massey Estates Limited | Real estate | 2021 |
| Mast Trading Ltd | Hospitality | 2019 |
| Mastella Ventures Limited | Other services | 2023 |
| Master 2 Drive Ltd | Education | 2025 |
| Master Chef (London) Ltd | Hospitality | 2019 |
| Master Developments Limited | Real estate | 2015 |
| Master Full Hands Ltd | Manufacturing | 2021 |
| Master Motorcycles Ltd | Wholesale & retail | 2022 |
| Master Pro Construct Ltd | Construction | 2026 |
| Mastermind Intelligence Centre International Limited | Education | 2023 |
| Mastermind Trading Limited | Real estate | 2001 |
| Matakov Ltd | Information & communication | 2018 |
| Math Star Tutors Ltd | Education | 2024 |
| Maths Tutor Essex Ltd | Education | 2024 |
| Maths'N Coach Ltd | Education | 2020 |
| Mati Scaffolding Ltd | Construction | 2025 |
| Matiq Innovation Studio Ltd | Information & communication | 2026 |
| Matmazel Ltd | Wholesale & retail | 2018 |
| Matriark CIC | Wholesale & retail | 2025 |
| Mattia&A Transport Ltd | Transport & logistics | 2022 |
| Matt’S Courier Service Ltd | Transport & logistics | 2026 |
| Mauritius Port Louis Assoc. (UK) CIC | Education | 2026 |
| Mausteve Limited | Health & social care | 2007 |
| Mavera Kitchen Ltd | Hospitality | 2025 |
| Maverix Impex Limited | Hospitality | 2024 |
| Mavi Kitchen Limited | Hospitality | 2025 |
| Mavicom Ltd | Real estate | 2011 |
| Mavish Limited | Wholesale & retail | 2009 |
| Mawoda Ltd | Other services | 2018 |
| Mawujayz Limited | Health & social care | 2009 |
| Mawz Services Ltd. | Administrative & support | 2016 |
| MAX Energy Solutions Ltd | Construction | 2018 |
| MAX Fashion Handbags Ltd | Wholesale & retail | 2018 |
| MAX Hospitality Ltd | Hospitality | 2026 |
| Max's Car Wash Ltd | Wholesale & retail | 2024 |
| Maxboxing UK Limited | Information & communication | 2008 |
| Maxcell Limited | Manufacturing | 2015 |
| Maxflow Ltd | Wholesale & retail | 2020 |
| Maxim Cafe Ltd | Hospitality | 2018 |
| Maximedia Marketing Ltd | Professional & scientific | 2011 |
| Maximillion Holding Limited | Other services | 2026 |
| Maximum Dance Design Limited | Arts & recreation | 2010 |
| Maximus Homes Ltd | Real estate | 2019 |
| Maximus Peers Limited | Health & social care | 2024 |
| Maxx Care Holdings Ltd | Financial services | 2024 |
| Maxx Holding Ltd | Financial services | 2014 |
| Maxy Wholesale Ltd | Wholesale & retail | 2026 |
| MAY Nails & Beauty Boutique Limited | Other services | 2023 |
| MAY Road Limited | Real estate | 2020 |
| Maybank Development Ltd | Professional & scientific | 2024 |
| Mayburn Limited | Information & communication | 2017 |
| Mayfair & Blackwell Property Maintenance Ltd | Construction | 2014 |
| Mayfair Lounge Ltd | Hospitality | 2026 |
| Mayfair Luxury Travel Limited | Administrative & support | 2022 |
| Mayfair Partners & Co Architectural Consultants Limited | Professional & scientific | 2025 |
| Mayfair Solutions (London) Ltd | Transport & logistics | 2002 |
| Mayka Barbers Limited | Other services | 2023 |
| Maynard Entertainment Ltd | Administrative & support | 2024 |
| Maypek Limited | Wholesale & retail | 2022 |
| Mayra General Beauty & Spa London Limited | Other services | 2024 |
| Maysmor Construction Ltd | Construction | 2025 |
| Mazeltovhair Limited | Wholesale & retail | 2026 |
| MB Autofix Ltd | Wholesale & retail | 2023 |
| MB Hairdresser Ltd | Other services | 2020 |
| MB Renovations & Design Ltd | Construction | 2025 |
| MB Wellness Group Ltd | Financial services | 2026 |
| Mb-Mi Investment LP | | 2016 |
| MBA Commercial Ltd | Financial services | 2024 |
| MBA Soup Ltd | Hospitality | 2025 |
| Mbale Holdings Limited | Financial services | 2022 |
| Mbay Mobility Ltd | Financial services | 2022 |
| MBB Events Ltd | Hospitality | 2019 |