| Maoters Furniture Ltd | Manufacturing | 2025 |
| Maphil International Ltd | Other services | 2020 |
| Mapvisibility Pros Ltd | Wholesale & retail | 2024 |
| Maqit Limited | Professional & scientific | 2006 |
| Maraecowell Ltd | Wholesale & retail | 2025 |
| Marahan Limited | Wholesale & retail | 2025 |
| Marali Design Ltd | Wholesale & retail | 2025 |
| Maraserti Trading Company Limited | Administrative & support | 2021 |
| Marber Kitson Limited | Administrative & support | 2024 |
| Marber Partnership LLP | | 2026 |
| Marble Communications Group Ltd | Construction | 2018 |
| Marble Music Ltd | Arts & recreation | 2018 |
| Marble Private Ltd | Professional & scientific | 2020 |
| Marchant’S Maintenance Service Ltd | Construction | 2022 |
| Marches Medical Services Ltd | Health & social care | 2013 |
| Marcont Group Ltd | Wholesale & retail | 2022 |
| Mardo Limited | Manufacturing | 2017 |
| Marfence Limited | Manufacturing | 2025 |
| Margine S Ltd | Manufacturing | 2025 |
| Mariam Legal Solutions Limited | Professional & scientific | 2025 |
| Mariamd Ltd | Health & social care | 2023 |
| Marine Coast Limited | Administrative & support | 2026 |
| Mario's Pizza Van Ltd | Hospitality | 2023 |
| Marita Designs Limited | Information & communication | 2013 |
| Mark Costar Limited | Extraterritorial | 2023 |
| Mark Leamy Ltd | Transport & logistics | 2015 |
| Market Central Ltd | Administrative & support | 2014 |
| Marketing Labs Europe Ltd | Professional & scientific | 2025 |
| Marl Hall Holdings Ltd | Real estate | 2022 |
| Marlmaise Homes Limited | Real estate | 2025 |
| Marlo Management & Consulting Ltd | Professional & scientific | 2024 |
| Marlow Boating Ltd | Administrative & support | 2024 |
| Marlow Ltd | Wholesale & retail | 2025 |
| Marmalade Brands Limited | Wholesale & retail | 2025 |
| Maroonretail Ltd | Wholesale & retail | 2025 |
| Marozi Ltd | Professional & scientific | 2024 |
| Marques Coaching Ltd | Arts & recreation | 2026 |
| Marrakech Metacraft Ltd | Other services | 2022 |
| Marriedtothemoney Ltd | Wholesale & retail | 2022 |
| Marrzon Ltd | Wholesale & retail | 2023 |
| Marshall Property Solutions Ltd | Households | 2018 |
| Marshall Psychology Ltd | Health & social care | 2025 |
| Marshalsey Consultancy Limited | Information & communication | 2025 |
| Marshalsey Properties Limited | Real estate | 2025 |
| MART4DESIGN Ltd | Construction | 2018 |
| Martamed Ltd | Wholesale & retail | 2026 |
| Martbae Ltd | Wholesale & retail | 2025 |
| Martleather Ltd | Wholesale & retail | 2021 |
| Maruf Media Publishing Limited | Wholesale & retail | 2022 |
| Marvel Solution Ltd | Information & communication | 2019 |
| Marvelinx Ltd | Information & communication | 2024 |
| Marvi Collections Ltd | Wholesale & retail | 2026 |
| Marview Praserail Ltd | Wholesale & retail | 2025 |
| Marvlientrade Ltd | Wholesale & retail | 2026 |
| Mary F Corry Limited | Education | 2016 |
| Masaab Ltd | Wholesale & retail | 2026 |
| Masaily Ltd | Extraterritorial | 2024 |
| Masena UK Limited | Information & communication | 2026 |
| Maskell Ltd | Professional & scientific | 2018 |
| Masq Trading Ltd | Information & communication | 2004 |
| Massar Lesley Ltd | Wholesale & retail | 2025 |
| Massless Ltd | Information & communication | 2021 |
| Master Accounts Ltd | Professional & scientific | 2019 |
| Master Signs Custom Works Ltd | Wholesale & retail | 2020 |
| Master Your Finances Limited | Professional & scientific | 2023 |
| Masterbuild Collective Ltd | Construction | 2026 |
| Mastq Properties Ltd | Real estate | 2024 |
| Matavyn Required Lists Ltd | Information & communication | 2026 |
| Matchaa Ltd | Wholesale & retail | 2025 |
| Matcore Solutions Ltd | Information & communication | 2026 |
| Materialist Wear Limited | Wholesale & retail | 2025 |
| Mathieu Business Solutions Ltd | Professional & scientific | 2026 |
| Matinaah Care International C.I.C. | Health & social care | 2026 |
| Matizfine Trading Co., Ltd | Extraterritorial | 2024 |
| Matjarnokhba Ltd | Wholesale & retail | 2025 |
| Matm Group Ltd | Wholesale & retail | 2025 |
| Matnetworks Events Limited | Education | 2025 |
| Matrix Digital Designs Limited | Information & communication | 2026 |
| Matrix Novo Technologies Co., Ltd. | Administrative & support | 2023 |
| Mattews Tech Co., Ltd | Wholesale & retail | 2023 |
| Matthews & Hoole Property Group Limited | Households | 2026 |
| Matthews Yard Events Limited | Arts & recreation | 2019 |
| Matthews Yard Trading Limited | Hospitality | 2019 |
| Matthews Yard Workspace Limited | Real estate | 2019 |
| Matthewsyard UK Limited | Arts & recreation | 2017 |
| Mattson Holdings Management Co., Ltd | Manufacturing | 2022 |
| Matuk Ltd | Information & communication | 2025 |
| Maveni Beauty Ltd | Wholesale & retail | 2025 |
| Maverick IT & Business Solutions Ltd | Information & communication | 2025 |
| MAX Azul Ltd | Professional & scientific | 2023 |
| MAX Goten Ltd | Wholesale & retail | 2026 |
| MAX Infinity Solutions Limited | Wholesale & retail | 2026 |
| MAX Sociedades Limited | Professional & scientific | 2021 |
| MAX Traducciones Ltd | Administrative & support | 2022 |
| Maxavion Ltd | Manufacturing | 2025 |
| Maxecomerce Group Ltd | Wholesale & retail | 2026 |
| Maxford Industry Co., Ltd | Administrative & support | 2019 |
| Maxim Culture Limited | Information & communication | 2024 |
| Maxluxxe Ltd | Wholesale & retail | 2025 |
| Maxs' Natural Therapies Ltd | Other services | 2026 |