| Msmz Investment Ltd | Real estate | 2024 |
| MSP Engineering Ltd | Professional & scientific | 2021 |
| Mssm Properties Ltd | Real estate | 2025 |
| MT5 Security Limited | Financial services | 2024 |
| MTA Healthcare Services Ltd | Health & social care | 2012 |
| MTL Cars Ltd | Wholesale & retail | 2015 |
| MTN Electrical Services Ltd. | Construction | 2015 |
| Mtrh Group Limited | Construction | 2025 |
| MTS Denco Limited | Administrative & support | 2011 |
| MTS Services IOW Ltd | Wholesale & retail | 2026 |
| MTW Plumbing and Heating Limited | Construction | 2017 |
| Mu-Technologies Limited | Manufacturing | 2002 |
| Mucky Pups Dog Grooming School and Salon Ltd | Education | 2021 |
| Mucuslesshealing Ltd | Wholesale & retail | 2025 |
| Muji & Daughter Ltd | Wholesale & retail | 2024 |
| Multi-Sport Social Health & Wellbeing C.I.C. | Health & social care | 2017 |
| Multicaat Limited | Professional & scientific | 2024 |
| Multimech Limited | Manufacturing | 2014 |
| Mundio Ltd | Financial services | 2026 |
| Murdon Properties Limited | Construction | 2003 |
| Murglo 2010 Limited | Real estate | 2010 |
| Murphy Business Recovery Ltd | Administrative & support | 2012 |
| Mursell (IW) Properties Limited | Real estate | 2017 |
| Muscat Property Group Ltd | Construction | 2026 |
| Muscle Academy Ltd | Other services | 2020 |
| Muse Hair Lounge Ltd | Other services | 2025 |
| Music for Welsh Schools CIC | Wholesale & retail | 2022 |
| Music House Entertainment Limited | Arts & recreation | 2016 |
| Must BE Ltd | Wholesale & retail | 2020 |
| Must BE Mobile Ltd | Wholesale & retail | 2024 |
| Mustis Buses Ltd | Transport & logistics | 2022 |
| Mutiny Shaving Ltd | Wholesale & retail | 2018 |
| MVC Technology Consulting Limited | Professional & scientific | 2020 |
| Mvgh Ltd | Hospitality | 2013 |
| MVH Cyber Consultancy Limited | Information & communication | 2023 |
| MVR Developments (Newport) Ltd | Professional & scientific | 2019 |
| MVR Solar Solutions Ltd | Construction | 2023 |
| MVR Solutions Limited | Construction | 2012 |
| MVS Watches Ltd | Wholesale & retail | 2023 |
| MW Forestry Ltd | Agriculture & fishing | 2015 |
| MWP Events Ltd | Construction | 2023 |
| MWVTF10 Limited | Transport & logistics | 2025 |
| MWW Ltd | Health & social care | 2021 |
| Mxbits Ltd | Wholesale & retail | 2021 |
| My ABC Piano Limited | Manufacturing | 2024 |
| My Beauty Art Ltd | Other services | 2023 |
| My Bookkeepers Online Limited | Professional & scientific | 2023 |
| My Build Quote Ltd | Information & communication | 2024 |
| My Club Collection Ltd | Wholesale & retail | 2020 |
| My Home Port Limited | Information & communication | 2012 |
| My Imagination IS Limited | Extraterritorial | 2022 |
| My Own Work Limited | Wholesale & retail | 2026 |
| My Salah Club Limited | Education | 2025 |
| My Salah MAT Limited | Manufacturing | 2018 |
| Mycrm Ltd | Information & communication | 2009 |
| Myles Services Limited | Other services | 2019 |
| Myna Logistics Limited | Transport & logistics | 2025 |
| Mypersonalremedy Limited | Education | 2025 |
| Mysuperfast Ltd | Information & communication | 2020 |
| Mytton Property Ltd | Real estate | 2025 |
| N & J Shipping Ltd | Transport & logistics | 2015 |
| N & N (Newport) Limited | | 2009 |
| N & S (SW) Limited | Wholesale & retail | 2006 |
| N Allard Developments Ltd | Construction | 2003 |
| N and a James Holdings Limited | Financial services | 2023 |
| N and I Transport Ltd | Transport & logistics | 2025 |
| N C Cross Limited | Health & social care | 2016 |
| N D & L Griffiths Limited | Construction | 2012 |
| N D Sport Performance Limited | Wholesale & retail | 2025 |
| N E Evans Brickwork Ltd | Construction | 2019 |
| N G Davies Ltd | Wholesale & retail | 2017 |
| N J Fixings Ltd | Construction | 2016 |
| N Meakin Contracts Ltd | Construction | 2009 |
| N W Corbin Limited | Construction | 2000 |
| N&R Foods Limited | Hospitality | 2025 |
| N&R Group Holdings (UK) Ltd | Financial services | 2024 |
| N2 Complete Property Management Limited | Administrative & support | 2012 |
| Naba Cuts Ltd | Other services | 2024 |
| NAC Interiors Ltd | Construction | 2023 |
| Nadeem K Foods Limited | Wholesale & retail | 2025 |
| Nagra Homes Limited | Real estate | 2021 |
| Nails at Cindy Limited | Other services | 2020 |
| Nails by Ceriann Ltd | Other services | 2023 |
| Naisfragrance Ltd | Wholesale & retail | 2025 |
| Najma Security Ltd | Administrative & support | 2017 |
| Najoke Enterprise Limited | Health & social care | 2015 |
| Namaste Bristol Ltd | Wholesale & retail | 2017 |
| Nancy Rose Limited | Financial services | 2012 |
| Nanoshine Ltd | Professional & scientific | 2024 |
| Nant-Y-Moor Park Limited | Arts & recreation | 2020 |
| NAP Management Ltd | Real estate | 2022 |
| Napoleon's Landing Management Limited | Households | 1999 |
| Narduzzo Limited | Wholesale & retail | 2012 |
| Narnia Limited | Hospitality | 2015 |
| Nars Healthcare Limited | Health & social care | 2015 |
| Nart 44 Ltd | Hospitality | 2026 |
| NAS24/7 Ltd | Wholesale & retail | 2026 |
| Nasa Nails Ltd | Other services | 2026 |
| Nasar & Co Estates Limited | Real estate | 2022 |
| Nasar & Co Trading Limited | Wholesale & retail | 2020 |