| Molomix Bioscience Limited | Manufacturing | 2020 |
| Momentum Health & Safety Consultants Limited | Professional & scientific | 2024 |
| Monarch Property Limited | Real estate | 2025 |
| Monforte Services Limited | Administrative & support | 2009 |
| Monitoringit (UK) Ltd | Other services | 2017 |
| Monkswood Securities Limited | Real estate | 1980 |
| Monmouth Health Limited | Health & social care | 2022 |
| Moonlighting Limited | Professional & scientific | 2000 |
| Moonshine Trading Limited | Wholesale & retail | 2018 |
| Mooracre Limited | Extraterritorial | 2026 |
| Moormire Limited | Extraterritorial | 2026 |
| Moral Training & Development Ltd | Professional & scientific | 2018 |
| Morgan Allen Site Services Limited | Professional & scientific | 2020 |
| Morgan Civils & Groundworks Limited | Construction | 2026 |
| Morgan Technical Services (South Wales) Ltd | Construction | 2019 |
| Morgan-Gould Properties Limited | Professional & scientific | 2003 |
| Morgannwg Investments Ltd | Financial services | 2024 |
| Morganparkes Electrical Ltd | Construction | 2021 |
| Morgans Bistro Limited | Hospitality | 2024 |
| Morris Line Engineering (Holdings) Limited | Manufacturing | 2018 |
| Morris Line Engineering Limited | Manufacturing | 2019 |
| Morris Wholesale Limited | Wholesale & retail | 2004 |
| Morris-Smith Property & Maintenance Ltd | Real estate | 2025 |
| Motherways Stores Ltd | Wholesale & retail | 2022 |
| Motive XQ Ltd | Manufacturing | 2020 |
| Motley Grapple Co Ltd | Arts & recreation | 2025 |
| Motorrad Tours Limited | Administrative & support | 2013 |
| Motorsave Bridgend Limited | Manufacturing | 2024 |
| Mountain View Legal Services Limited | Other services | 2026 |
| Movereturn Limited | Transport & logistics | 1989 |
| Moxie Skins Ltd | Wholesale & retail | 2025 |
| MP Dynamics Ltd | Construction | 2023 |
| Mprl Limited | Professional & scientific | 2015 |
| MPS Ecology Ltd | Professional & scientific | 2023 |
| MPS Installations (Wales) Ltd | Construction | 2013 |
| MR Big Bites Limited | Hospitality | 2020 |
| MR Blinds (South Wales) Limited | Manufacturing | 2020 |
| MR Parcels Delivery Ltd | Transport & logistics | 2020 |
| MR Sparks Limited | Construction | 2017 |
| MR T. D. Owen Limited | Health & social care | 2003 |
| MRA Fast Food Ltd | Hospitality | 2023 |
| MRM Mechanical Limited | Manufacturing | 2016 |
| MRN Company Limited | Transport & logistics | 2025 |
| MRO Support Ltd | Wholesale & retail | 2017 |
| MS Waste Managment Limited | Water & waste | 2026 |
| Msav Consultancy Ltd | Wholesale & retail | 2023 |
| MSD Independent Limited | Education | 2016 |
| Msmart Electrical Ltd | Construction | 2018 |
| MTC70 Limited | Public administration | 2024 |
| MTD Diagnostics Ltd | Health & social care | 2018 |
| Mthandyman Ltd | Construction | 2020 |
| Mulfran Limited | Real estate | 2025 |
| Mumbles Dental and Cosmetic Suite (RG) Limited | Health & social care | 2011 |
| Mummy & ME Boutique Ltd | Wholesale & retail | 2026 |
| Munch Time Ltd | Professional & scientific | 2025 |
| Munchies Limited | Manufacturing | 1998 |
| Murphy & Shill Ltd | Construction | 2024 |
| Mushroom Holdings Ltd | Real estate | 2018 |
| Musical Instrument Support Ltd | Manufacturing | 2025 |
| MW MOT & Service Centre Ltd | Wholesale & retail | 2023 |
| MW Property Ventures Ltd | Real estate | 2021 |
| MW Vehicle Services Ltd | Wholesale & retail | 2020 |
| MX6 Property Ltd | Real estate | 2019 |
| Mybizonline Ltd | Information & communication | 2017 |
| Mycoderm Limited | Health & social care | 2012 |
| N & BEE Holdings Limited | Financial services | 2013 |
| N R Parsons Transport Limited | Transport & logistics | 2003 |
| N-Ergy Group Limited | Professional & scientific | 2007 |
| N.T.D. Contractors Limited | Construction | 1972 |
| Nagar Property Ltd | Real estate | 2021 |
| Nails by Shan CYF | Other services | 2025 |
| Namo EAT Ltd | Hospitality | 2020 |
| Namy 2024 Ltd | Other services | 2024 |
| Nanog Limited | Health & social care | 2025 |
| Nant-Y-Moel Community Centre and Wyndham Bowling Club Limited | Arts & recreation | 2020 |
| Nantymoel RFC Limited | Arts & recreation | 2018 |
| Naplit Limited | Information & communication | 2025 |
| Narbeth's Mechanical Services Limited | Construction | 1998 |
| Narbeths Properties Limited | Real estate | 2019 |
| Narbeths Property Services Limited | Real estate | 2019 |
| Narelle Cowan Ltd | Information & communication | 2024 |
| Narra Consulting Limited | Administrative & support | 2019 |
| NAS Medical Ltd | Health & social care | 2019 |
| Nashville Food Group Limited | Wholesale & retail | 2015 |
| Nashville Food Holdings Ltd | Financial services | 2024 |
| Natasha Bray Ltd | Education | 2016 |
| Nathaniel Property Developments Limited | Real estate | 2007 |
| National Children's Choir of Great Britain | Arts & recreation | 2001 |
| National Leisure Limited | Extraterritorial | 1993 |
| Natmac Limited | Arts & recreation | 2008 |
| Natsuttpub Ltd | Hospitality | 2026 |
| Natural Electrix Ltd | Administrative & support | 2025 |
| Navitas Solutions Group Limited | Manufacturing | 2023 |
| Naytech Ltd | Manufacturing | 2024 |
| NAZ Bridgend Ltd | Hospitality | 2026 |
| NB Fitness Ltd | Arts & recreation | 2017 |
| NB Railfix Ltd | Construction | 2015 |
| NC Properties Bridgend Ltd | Real estate | 2020 |
| Nearest Beer Shop Limited | Wholesale & retail | 2023 |
| Neatcray Limited | Extraterritorial | 2026 |