| Morgan James Property Limited | Construction | 2021 |
| Morgana Property Ltd | Real estate | 2025 |
| Moroni Enterprises Limited | Financial services | 2018 |
| Morris Molloy Limited | Professional & scientific | 2016 |
| Morrow London Limited | Wholesale & retail | 2026 |
| Mortgage Plan Limited | Financial services | 2019 |
| Mortgage Required Limited | Financial services | 2008 |
| Moss Legal Limited | Professional & scientific | 2020 |
| Moss Management Ltd | Construction | 2023 |
| Moss Penny (UK) Limited | Professional & scientific | 2004 |
| Mothermode Limited | Information & communication | 2026 |
| Moti Property Limited | Financial services | 2024 |
| Motioneager Limited | Professional & scientific | 1996 |
| Motor & Craft Limited | Transport & logistics | 2020 |
| Motor 100 Limited | Transport & logistics | 2026 |
| Motor Movements Limited | Transport & logistics | 2025 |
| Motornova Cars Ltd | Wholesale & retail | 2026 |
| Motorsport NOW Limited | Arts & recreation | 2006 |
| Motus Mediation Ltd | Professional & scientific | 2024 |
| Mount Carmel Limited | Hospitality | 2021 |
| Mount Gould Properties Ltd | Real estate | 2025 |
| Mouse Inc Limited | Arts & recreation | 2004 |
| Move Happy Fitness Ltd | Arts & recreation | 2025 |
| Move More Pro Ltd | Wholesale & retail | 2022 |
| Mpelec Ltd | Construction | 2020 |
| MPM Key Services Ltd | Other services | 2017 |
| MPM Legal Solutions Limited | Professional & scientific | 2012 |
| MPM4SCM Ltd | Other services | 2026 |
| MPP Property Services Limited | Real estate | 2024 |
| Mpsic Ltd | Health & social care | 2022 |
| MPW R&R Ltd | Professional & scientific | 2014 |
| MR Alfresco & TJD Limited | Construction | 2018 |
| MR Art 13 Limited | Construction | 2021 |
| MR Bridger Enterprises Limited | Manufacturing | 2005 |
| MR James of Marlow Limited | Wholesale & retail | 2020 |
| MR Leungs UK Ltd | Hospitality | 2020 |
| MRC Developments Limited | Professional & scientific | 1969 |
| MRM Education Services LLP | | 2024 |
| MS Ansar Consultancy Limited | Information & communication | 2025 |
| MS Dhanjal Consulting Ltd | Financial services | 2026 |
| MS Logic Consultancy Limited | Administrative & support | 2017 |
| Msbw Limited | Financial services | 2017 |
| MSD Accountancy Limited | Professional & scientific | 2005 |
| Msquare Elite Limited | Information & communication | 2009 |
| Mstj Group Ltd | Other services | 2024 |
| MSW Consults Limited | Administrative & support | 2014 |
| MTG09 Ltd | Wholesale & retail | 2025 |
| MTN Consulting Solutions Limited | Professional & scientific | 2022 |
| MTR Management Services Ltd | Households | 2013 |
| Mufc Limited | Real estate | 2020 |
| Mulberry&Orchard Ltd | Administrative & support | 2020 |
| Mullan Properties Limited | Real estate | 2018 |
| Mullane Property Ltd | Real estate | 2024 |
| Mullino Limited | Hospitality | 2019 |
| Multitude Productions Limited | Arts & recreation | 2024 |
| Munich Motors Limited | Wholesale & retail | 2003 |
| Murex Biotech Limited | Manufacturing | 1991 |
| Murmac Electrical Ltd | Construction | 2025 |
| Murphy ENG Ltd | Professional & scientific | 2025 |
| Murray Home Property Ltd | Real estate | 2021 |
| Murraymount Limited | Real estate | 2014 |
| Muscle Massacre Ltd | Arts & recreation | 2025 |
| Mushin Global Limited | Arts & recreation | 2011 |
| Musica Europa Limited | Administrative & support | 2019 |
| Musindo Professional Services Ltd | Health & social care | 2014 |
| Muzdahir Limited | Real estate | 2020 |
| MV Consulting Limited | Professional & scientific | 2003 |
| MVT Subsea Consulting Limited | Administrative & support | 2017 |
| MXN Limited | Administrative & support | 2006 |
| My Business Address Limited | Wholesale & retail | 2025 |
| My Facilities Management Ltd | Real estate | 2023 |
| My Home Office Limited | Information & communication | 2003 |
| My Legal Limited | Professional & scientific | 2014 |
| My Little Green Wardrobe Ltd | Wholesale & retail | 2021 |
| My Local Property Ltd | Information & communication | 2013 |
| My Motor Group Ltd | Wholesale & retail | 2026 |
| My Pilates House Ltd | Education | 2024 |
| Myadhdtracker Ltd | Information & communication | 2025 |
| Mybiome Limited | Health & social care | 2022 |
| Mycroft Advisory Ltd | Professional & scientific | 2024 |
| Myemina Investments Limited | Real estate | 2024 |
| Mygreensquares Ltd | Information & communication | 2023 |
| Mygynaecologist Ltd | Health & social care | 2026 |
| Myll Mead Limited | Extraterritorial | 2015 |
| Myno Limited | Real estate | 2024 |
| Myphonecase Limited | Households | 2013 |
| Myphotostation Limited | Wholesale & retail | 2021 |
| Mypolicyvault Ltd | Information & communication | 2025 |
| Myra Aesthetics Ltd | Professional & scientific | 2024 |
| Mytherapyspace Ltd | Health & social care | 2025 |
| Mythos Labs Limited | Information & communication | 2025 |
| Mywisehub Limited | Information & communication | 2017 |
| Myworkspot Limited | Real estate | 2016 |
| MZM Associates Ltd | Professional & scientific | 2018 |
| N & G Remapping Limited | Extraterritorial | 2017 |
| N & S Oral Care Ltd | Health & social care | 2018 |
| N a Services Limited | Manufacturing | 1998 |
| N D a First AID Training Ltd | Education | 2015 |
| N Lingham-Clark Ltd | Construction | 2025 |
| N.V. Mycom Europe S.A. | | 1998 |