| Motorcycles Masters UK Limited | Wholesale & retail | 2023 |
| Motors International Limited | Wholesale & retail | 2000 |
| Motosales Ltd | Professional & scientific | 2004 |
| Motovault Limited | Wholesale & retail | 2026 |
| Mount Zion Health Care Ltd | Health & social care | 2018 |
| Mount Zion Prayer House Limited | Health & social care | 2009 |
| Mountcray Limited | Households | 1977 |
| Mouzakis Construction Ltd | Construction | 2022 |
| Move N Trade Ltd | Construction | 2024 |
| Moving Forward Digital Solutions UK Ltd | Information & communication | 2025 |
| Moving Forward Support Services Ltd | Administrative & support | 2023 |
| Moving Lives Forward Ltd | Transport & logistics | 2024 |
| Movip Homes Ltd | Health & social care | 2024 |
| Movix Productions Ltd | Information & communication | 2024 |
| Mowad Ltd | Wholesale & retail | 2024 |
| Mowo Services Limited | Health & social care | 2005 |
| Moxera Trade Ltd | Wholesale & retail | 2026 |
| Moxie Developments Rentals Ltd | Real estate | 2019 |
| Mpid Limited | Administrative & support | 2025 |
| MPR Estates Ltd | Real estate | 2018 |
| MQF Construction Ltd | Construction | 2015 |
| MR Abul Hussain Ltd | Real estate | 2024 |
| MR Captain Ltd | Construction | 2020 |
| MR Chilled Ltd | Wholesale & retail | 2020 |
| MR Chippy Essex Ltd | Hospitality | 2025 |
| MR Computer Solutions Limited | Other services | 2008 |
| MR GB Glass Solutions Ltd | Wholesale & retail | 2020 |
| MR Marvel Entertainments Limited | Arts & recreation | 2003 |
| MR Rams Chelmsford Ltd | Hospitality | 2024 |
| MR Recoveryman Ltd | Wholesale & retail | 2007 |
| MR Shiner Ltd | Administrative & support | 2025 |
| MR Volta Electrical Ltd | Construction | 2019 |
| MRA Professional Services Ltd | Health & social care | 2013 |
| MRB Engineers Ltd | Construction | 2013 |
| Mrcxl Limited | Real estate | 2025 |
| Mrgb Property Investments UK Ltd | Real estate | 2020 |
| MRM Bulding Pro Ltd | Construction | 2025 |
| MRN Property Investments Limited | Real estate | 2016 |
| MRT Property Group Limited | Real estate | 2023 |
| MRT Windows London Limited | Construction | 2025 |
| MS Cyber Security Ltd | Information & communication | 2021 |
| MS Karim Properties Limited | Real estate | 2024 |
| MS Resources Ltd | Transport & logistics | 2021 |
| MS UK Construction Ltd | Construction | 2024 |
| MSD Business Ltd | Wholesale & retail | 2024 |
| MSF Care Services Limited | Health & social care | 2025 |
| Msft Limited | Arts & recreation | 2011 |
| MSI Group Limited | Administrative & support | 2006 |
| MSK Developers Limited | Real estate | 2015 |
| MSK Internationals UK Ltd | Administrative & support | 2016 |
| MSK Managing Agents Limited | Real estate | 2017 |
| MSM & SON Properties Ltd | Real estate | 2022 |
| MSO Lofts Limited | Construction | 2018 |
| Msooky Trading Ltd | Financial services | 2026 |
| MSR Pizza Ltd | Hospitality | 2025 |
| MT Adds Ltd | Professional & scientific | 2022 |
| MT Best Tutoring World Limited | Education | 2025 |
| MT Detailing Limited | Wholesale & retail | 2024 |
| MT Networks Ltd | Information & communication | 2024 |
| MT Trade Ltd | Other services | 2019 |
| MT01 Ltd | Construction | 2026 |
| MTB Entertainment Ltd | Information & communication | 2019 |
| MTG Electrical Services Ltd | Construction | 2021 |
| MTM Estates Ltd | Real estate | 2025 |
| MTX Source Ltd | Wholesale & retail | 2025 |
| Mubarak London Limited | Wholesale & retail | 2015 |
| Mubash Global Services Limited | Real estate | 2020 |
| Mubinah Technologies Ltd | Information & communication | 2018 |
| Mucs Properties Limited | Real estate | 2017 |
| Mufengii Limited | Manufacturing | 2024 |
| Mujy Limited | Administrative & support | 2024 |
| Mukeshkansara Ltd | Professional & scientific | 2026 |
| Mulan NW9 Limited | Other services | 2023 |
| Mullet Catering Ltd | Hospitality | 2026 |
| Multi-Ballers FC Ltd | Education | 2024 |
| Multi-Grace Limited | Households | 2014 |
| Multimart Ecommerce Ltd | Wholesale & retail | 2023 |
| Mumin Management Limited | Wholesale & retail | 2018 |
| Mumsing Choir Community Interest Company | Arts & recreation | 2025 |
| Munchworks Catering Limited | Hospitality | 2026 |
| Munns & Sons Limited | Extraterritorial | 2002 |
| Munns (Building Services) Limited | Extraterritorial | 2002 |
| Munns (Electrical Contractors) Limited | Extraterritorial | 2002 |
| Munns Group Limited | Construction | 2000 |
| Munns Limited | Construction | 1975 |
| Munshiganj Zila Nationalist Forum UK | Financial services | 2025 |
| Muntaha Group Ltd | Wholesale & retail | 2025 |
| Muro (Cafe) Limited | Hospitality | 2018 |
| Murray Brothers Properties Limited | Real estate | 1987 |
| Murray Health and Medical Ltd | Health & social care | 2022 |
| Murt Solutions Ltd | Wholesale & retail | 2019 |
| Murugan Construction Ltd | Construction | 2015 |
| Musa & Subhaan Limited | Transport & logistics | 2025 |
| Muscle HUG YK Ltd | Health & social care | 2026 |
| Muscle Leisure Ltd | Other services | 2019 |
| Muscle Workout Limited | Other services | 2016 |
| Music Gems Ltd | Information & communication | 2019 |
| Musica Baltica Ltd | Information & communication | 2023 |
| Mussit Ltd | Wholesale & retail | 2015 |
| Mustaf Investment Properties Ltd | Real estate | 2024 |