| Morris Publishing Limited | Information & communication | 1946 |
| Morris Racing Limited | Arts & recreation | 2014 |
| Morticus Ltd | Professional & scientific | 2025 |
| Moss Motorsport Composites Limited | Manufacturing | 2013 |
| Motion Publishing Limited | Information & communication | 2019 |
| Moto-Drift Limited | Transport & logistics | 2013 |
| Motomindz CIC | Education | 2025 |
| Motorworx Car Storage Ltd | Transport & logistics | 2025 |
| Mount Pleasant Services Ltd | Professional & scientific | 2025 |
| Movations Limited | Manufacturing | 2023 |
| MOVE2YOU Ltd | Transport & logistics | 2023 |
| Movo Sameday Ltd | Transport & logistics | 2025 |
| MP Electrical (Oxon) Limited | Construction | 2015 |
| MP Jobs Ltd | Administrative & support | 2013 |
| MR Punch Audiobooks Ltd | Information & communication | 2021 |
| MRK Buildco Ltd | Construction | 2026 |
| MRS Magnetics Limited | Manufacturing | 2014 |
| MRS Potato Head Limited | Hospitality | 2025 |
| MS Britannica Ltd | Real estate | 2022 |
| MSB Services Limited | Construction | 2016 |
| MSL Taxis Ltd | Transport & logistics | 2025 |
| Mt-Spaces Ltd | Administrative & support | 2005 |
| MTM Company a Limited | Professional & scientific | 2025 |
| MTW Consultancy Services Ltd | Administrative & support | 2022 |
| Muca General Builders Ltd | Construction | 2024 |
| Muddy Spades Limited | Administrative & support | 2023 |
| Multi Channel Limited | Professional & scientific | 2023 |
| Multi-Channel Skills Ltd | Information & communication | 2015 |
| Multinella Ltd | Wholesale & retail | 2025 |
| Mumby's Live-In Care Limited | Health & social care | 2002 |
| Mumbys Introductory Live-In Care Service Limited | Health & social care | 2018 |
| Mummies Alive (UK) Limited | Information & communication | 2014 |
| Mummymusthave Ltd | Wholesale & retail | 2024 |
| Muncer Consulting Limited | Other services | 2021 |
| Munch @ the LOG Cabin Limited | Hospitality | 2015 |
| Munden Consultancy Limited | Wholesale & retail | 2015 |
| Muppets and Whatnots Ltd | Arts & recreation | 2023 |
| Murphy and Grace Limited | Arts & recreation | 2016 |
| MW Learning Ltd | Information & communication | 2023 |
| Mwmw Ltd | Arts & recreation | 2025 |
| MWTW25 Limited | Real estate | 2025 |
| My Medical Department Ltd | Professional & scientific | 2014 |
| My Music Store Limited | Wholesale & retail | 2018 |
| My Rockerbox Limited | Information & communication | 2020 |
| Myaidepartments Ltd | Wholesale & retail | 2025 |
| Mycablebox Ltd | Wholesale & retail | 2009 |
| Myhomekeepers Limited | Administrative & support | 2019 |
| Myodynamics Ltd | Health & social care | 2011 |
| Myriad IT Recruitment Limited | Extraterritorial | 1982 |
| Myrrh & Thyme Ltd | Real estate | 2019 |
| Myter Construction Ltd | Construction | 2022 |
| N and S Ventures Limited | Real estate | 2017 |
| N Marcos Ltd | Transport & logistics | 2018 |
| N&T Limited | Real estate | 2021 |
| N. Scott Accident Repair Limited | Wholesale & retail | 2024 |
| Nails 2 Envy Ltd | Other services | 2026 |
| Naked Nectar Ltd | Hospitality | 2024 |
| Napier Court M.C. (Abingdon) Limited | Professional & scientific | 1989 |
| NAT Transport Ltd | Transport & logistics | 2015 |
| National Communications Group Limited | Information & communication | 1996 |
| Natural Stone Craft Limited | Construction | 2008 |
| Navigating HR Limited | Professional & scientific | 2025 |
| Navigating IT ALL Limited | Professional & scientific | 2024 |
| Navitas SAE Holdings Limited | Financial services | 2022 |
| Navitas UK Holdings Limited | Education | 2006 |
| Navy Black Ltd | Arts & recreation | 2023 |
| NDJ Housing Ltd | Real estate | 2025 |
| Ne&N Limited | Information & communication | 2023 |
| Nebula Education Ltd | Information & communication | 2020 |
| Nemo Engineering Ltd. | Professional & scientific | 2016 |
| Neonhos Software Ltd | Wholesale & retail | 2025 |
| Neovac Ltd | Professional & scientific | 2021 |
| Neptune Sports Management Limited | Arts & recreation | 2019 |
| Neterian Limited | Information & communication | 2006 |
| Network Point Management (Witney) Limited | Real estate | 2001 |
| Neuro-Bio Ltd | Professional & scientific | 2013 |
| New AGE Inc Ltd | Information & communication | 2024 |
| New Chapter Solutions Limited | Information & communication | 2017 |
| New England Biolabs Lyophilization Sciences Ltd. | Administrative & support | 2011 |
| New Inn Services Limited | Financial services | 2024 |
| Newcombe & Sons Limited | Professional & scientific | 2024 |
| Newcrowd Ltd | Other services | 2014 |
| Newlus Limited | Professional & scientific | 2002 |
| Newnet Limited | Extraterritorial | 2016 |
| Newstar Innovation Ltd | Professional & scientific | 2021 |
| Newton Consultancy Limited | Extraterritorial | 2024 |
| Newton Consultants Limited | Extraterritorial | 2024 |
| Newton Consulting Group Limited | Extraterritorial | 2023 |
| Newton Consulting International Limited | Extraterritorial | 2024 |
| Newton Consulting Limited | Professional & scientific | 2001 |
| Newton Europe Bidco Limited | Professional & scientific | 2021 |
| Newton Europe Limited | Extraterritorial | 2022 |
| Newton Europe Midco Limited | Professional & scientific | 2021 |
| Newton Group Holdings Limited | Professional & scientific | 2021 |
| Newton Group International Limited | Extraterritorial | 2026 |
| Newton Holdco Limited | Professional & scientific | 2021 |
| Newton Impact Limited | Extraterritorial | 2023 |
| Newton Industrial Consultants Holdings Limited | Professional & scientific | 2011 |
| Newton International Limited | Extraterritorial | 2023 |
| Nexeon Limited | Manufacturing | 2006 |