| MMK Civil Engineering Ltd. | Construction | 2007 |
| MMK Group Ltd | Real estate | 2020 |
| MML Coaching Ltd | Other services | 2024 |
| MN Industrial Flooring Ltd | Construction | 2018 |
| MNM PCN Limited | Health & social care | 2022 |
| MNR Medical Services Limited | Health & social care | 2025 |
| Mobilityco Healthcare Group Limited | Financial services | 2024 |
| Mobilityco Ltd | Wholesale & retail | 2020 |
| Mobitechs Wilmslow Limited | Wholesale & retail | 2023 |
| Mockingbird Developments Limited | Real estate | 2009 |
| Moco Homes Limited | Wholesale & retail | 2023 |
| Modern Cloud Consulting Ltd | Professional & scientific | 2024 |
| Modular Roofing Solutions Ltd | Professional & scientific | 2023 |
| Modulus Recruitment Limited | Administrative & support | 2017 |
| Mohsha MCR Ltd | Manufacturing | 2025 |
| Moid Media Limited | Information & communication | 2020 |
| Monaghan Climate Services Ltd | Construction | 2026 |
| Monarch Construction Management Ltd | Construction | 2019 |
| Monday 9AM Ltd | Information & communication | 2009 |
| Monday Club Hospitality Ltd | Hospitality | 2020 |
| Mongoose Cyber Security Ltd | Information & communication | 2022 |
| Monkey Nuts Garage Ltd | Wholesale & retail | 2025 |
| Mono Carbon Limited | Professional & scientific | 2024 |
| Monolith Design Ltd | Professional & scientific | 2025 |
| Montgomery Cowen Limited | Other services | 2018 |
| Montmano Properties Ltd | Real estate | 2019 |
| Moonbeam Homes Limited | Real estate | 2022 |
| Moonbeam Investments Limited | Other services | 2021 |
| Moore Secure Limited | Construction | 1999 |
| Moore Secure Solutions Ltd | Administrative & support | 2021 |
| Moorside Place (Management Company) NO.1 Limited | Households | 2009 |
| Moreira Meah Ltd | Administrative & support | 2024 |
| Morethansports Coaching Ltd | Arts & recreation | 2026 |
| Morgan Orthopaedics Ltd | Health & social care | 2019 |
| Morris (Deysbrook) Limited | Extraterritorial | 2003 |
| Morris (Warwick) Limited | Extraterritorial | 2003 |
| Morris Developments (North) Limited | Construction | 1985 |
| Morris Group Limited | Professional & scientific | 2004 |
| Morris Health Solutions Consulting Limited | Administrative & support | 2015 |
| Morris Homes (Kettering) Limited | Construction | 1994 |
| Morris Homes (Midlands) Limited | Construction | 1922 |
| Morris Homes (Milton Keynes) Limited | Professional & scientific | 2005 |
| Morris Homes (North) Limited | Construction | 1964 |
| Morris Homes (West Midlands) Limited | Construction | 1990 |
| Morris Homes (Winnington) Limited | Construction | 2000 |
| Morris Homes Developments Limited | Construction | 1987 |
| Morris Homes Group Limited | Other services | 2021 |
| Morris Homes Limited | Construction | 1998 |
| Morris Ventures Limited | Construction | 2003 |
| Morritt Holdings Limited | Financial services | 2023 |
| Morritt Medical Limited | Extraterritorial | 2025 |
| Mort-Tech Ltd | Professional & scientific | 2026 |
| Mortgage Savers Limited | Financial services | 1999 |
| Morton Interim Health Management Limited | Professional & scientific | 2012 |
| Mosaic Films Production Ltd | Professional & scientific | 2025 |
| Mosaic Private Equity (Nominees) Limited | Professional & scientific | 2007 |
| Mosaic Private Equity Limited | Administrative & support | 2006 |
| Motionary Ltd | Information & communication | 2025 |
| MOTOR44.COM Ltd. | Wholesale & retail | 2019 |
| Mount Medical Limited | Health & social care | 2023 |
| Move Ahead Media Limited | Administrative & support | 2019 |
| Movementum Natural Health Systems Ltd | Manufacturing | 2020 |
| Mozhgan Ltd | Other services | 2013 |
| MP Performance Limited | Other services | 2026 |
| MP26 Ltd | Hospitality | 2026 |
| MPE Orbur Group Limited | Professional & scientific | 2012 |
| Mpht Limited | Health & social care | 2019 |
| MR a Watts Limited | Health & social care | 2012 |
| MR Baker's WM Limited | Hospitality | 2018 |
| MR Flavour Drinks Ltd | Administrative & support | 2023 |
| MR J P Byrne Limited | Health & social care | 2015 |
| MR M Madan Limited | Health & social care | 2019 |
| MR Neil Walker Limited | Health & social care | 2018 |
| MR Qureshi Limited | Health & social care | 2014 |
| MR R C Young Limited | Health & social care | 2013 |
| MR R Paul Harris Ltd | Health & social care | 2019 |
| MR Simon P Hargreaves Limited | Health & social care | 2010 |
| MR Tuabin Rasheed Limited | Health & social care | 2015 |
| Mram Ltd | Health & social care | 2014 |
| MRB Media Ltd | Professional & scientific | 2026 |
| MRK5 Fitness Limited | Arts & recreation | 2021 |
| MRW Capital Ltd | Professional & scientific | 2026 |
| Ms.Nayak Limited | Health & social care | 2020 |
| MSK Commercial Ltd | Real estate | 2025 |
| Mspme Limited | Information & communication | 2022 |
| Mswk IT Service Solutions Ltd | Information & communication | 2017 |
| MT Fire Protection Ltd | Construction | 2021 |
| MT Medicolegal Ltd | Health & social care | 2022 |
| MTT Online Retail Limited | Administrative & support | 2022 |
| MTT Retail Consultancy Limited | Professional & scientific | 2022 |
| MTX Contracts Limited | Construction | 2002 |
| MTX Holdings Limited | Financial services | 2015 |
| MUD 11 Ground Maintenance Limited | Administrative & support | 2026 |
| Muffauto Limited | Wholesale & retail | 2025 |
| Muffdrive Ltd | Administrative & support | 2025 |
| Muffwash Ltd | Wholesale & retail | 2025 |
| Mukuma Limited | Health & social care | 2025 |
| Multipack Foods Ltd | Other services | 2015 |
| Multipack Logistics Ltd | Administrative & support | 2014 |
| Multisports Coaching Limited | Education | 2023 |