| Long Xing Ltd | Hospitality | 2021 |
| Lotus Fish Limited | Hospitality | 2026 |
| Lpgas 4 Wales Limited | Energy | 2013 |
| Lrpx Ltd | Professional & scientific | 2025 |
| LSJ Trading Ltd | Administrative & support | 2018 |
| LSN Diffusion Limited | Manufacturing | 2012 |
| Lucas George Ltd | Other services | 2024 |
| LUX Focus Limited | Construction | 2019 |
| LUX Neon Investments Ltd | Financial services | 2025 |
| LV Installations Ltd | Manufacturing | 2021 |
| LWA Properties Limited | Construction | 2023 |
| M and M Garage (Llandeilo) Limited | Wholesale & retail | 2019 |
| M Husemann Builders Ltd | Construction | 2025 |
| M J Motors Limited | Wholesale & retail | 2002 |
| M Paterson Trading Ltd | Professional & scientific | 2025 |
| M Thomas & Sons Ltd | Construction | 2019 |
| M W Griffiths & SON Limited | Wholesale & retail | 2002 |
| M.A.X Homes Ltd | Real estate | 2024 |
| M.E.T Property Group Ltd | Construction | 2022 |
| M4W Financial Services Ltd | Financial services | 2025 |
| Maccare Limited | Health & social care | 2022 |
| Mainwarings Developments Limited | Construction | 2021 |
| Mainwarings Groundwork & Construction Limited | Construction | 2021 |
| Mainwarings Holdings Limited | Financial services | 2023 |
| Malihera Limited | Health & social care | 2017 |
| Mallon Cars Limited | Wholesale & retail | 2014 |
| Mama Glam Ltd | Wholesale & retail | 2024 |
| Mamamaia Events Ltd | Administrative & support | 2025 |
| Managed Intelligence Solutions Ltd | Information & communication | 2025 |
| Manford House Limited | Hospitality | 2003 |
| Manor Road Garage Limited | Wholesale & retail | 2002 |
| Manshield Ecotherapy CIC | Health & social care | 2024 |
| Marc's Motors Limited | Wholesale & retail | 2009 |
| Marley Cwmgors Property Ltd | Real estate | 2016 |
| Marmara Barber Shop Ltd | Other services | 2023 |
| Marmath Ltd | Financial services | 2026 |
| Marsden Hill Limited | Health & social care | 2010 |
| Massive Properties Ltd | Real estate | 2021 |
| Masters Partnership Ltd | Construction | 2020 |
| Mattniel Limited | Wholesale & retail | 2025 |
| Maven Industries Limited | Information & communication | 2023 |
| MBN Building Contractor Ltd | Manufacturing | 2025 |
| Mclean Company Group Limited | Financial services | 2024 |
| Media Story Productions Limited | Arts & recreation | 2020 |
| Meester Consult Ltd | Professional & scientific | 2025 |
| Meester Green Ltd | Construction | 2026 |
| Meester Group UK Ltd | Construction | 2026 |
| Meester Properties UK Ltd | Construction | 2026 |
| Meithrinfa Andi Pandi's Day Nursery Ltd | Health & social care | 2025 |
| Meithrinfa Jac-Y-Do Limited | Health & social care | 2016 |
| Mentro CYF | Construction | 2016 |
| Meosmo Ltd | Manufacturing | 2014 |
| Merchsend Limited | Professional & scientific | 2020 |
| Mercury Accounting & Financial Services Ltd | Professional & scientific | 2022 |
| Mercury Aerospace Limited | Other services | 2015 |
| Merlins Medieval Closet Limited | Wholesale & retail | 2015 |
| Mess UP the Mess Theatre Company Ltd | Arts & recreation | 2007 |
| Michael Parry Consulting LLP | | 2012 |
| Michael W. Tench & SON Building Contractors Limited | Construction | 2013 |
| Midnight Motorsport Ltd | Wholesale & retail | 2025 |
| Midtec Products Limited | Manufacturing | 2004 |
| Miela Group Ltd | Real estate | 2025 |
| Mike Harrison Ltd. | Information & communication | 2011 |
| Mike Tench Properties Ltd | Real estate | 2018 |
| Mike Voyle Electrical Ltd | Construction | 2020 |
| Millers Group Holdings Limited | Financial services | 2023 |
| Mindfulness Health Limited | Health & social care | 2014 |
| MIP Global Ltd | Information & communication | 2025 |
| MIP UK Services Ltd | Information & communication | 2025 |
| Miscemmo Limited | Manufacturing | 2020 |
| Mitec Telecom Group Ltd | Information & communication | 2021 |
| MLK Platinum Consultancy Ltd | Professional & scientific | 2026 |
| MNR Civils & Consultancy Ltd | Construction | 2026 |
| Morgan 316 Engineering Services Limited | Professional & scientific | 2013 |
| Morgan Carpenter Limited | Real estate | 2024 |
| Morgan Electrical Engineering Limited | Construction | 2024 |
| Morgan Financial Practice Limited | Financial services | 2003 |
| Morgan Marine Limited | Manufacturing | 1965 |
| Morgan Roadside Limited | Manufacturing | 2024 |
| Morgan Steel Limited | Manufacturing | 2024 |
| Morgan Training Limited | Education | 2024 |
| Mountain Rose Ltd. | Manufacturing | 2002 |
| Mountain Vets Limited | Professional & scientific | 2021 |
| Mountain View Feeds Ltd | Wholesale & retail | 2019 |
| Mpsisjlt Ltd | Hospitality | 2017 |
| MSD Autocentre Ltd | Wholesale & retail | 2008 |
| Mttm Developments Limited | Real estate | 2026 |
| My Life My Support Limited | Health & social care | 2021 |
| Mycobio Ltd | Hospitality | 2024 |
| N.S. Waller Limited | Construction | 1997 |
| Nant Melyn Carpentry Ltd | Construction | 2019 |
| Nantstream Limited | Financial services | 2022 |
| Naomi Jones Curl Academy Ltd | Education | 2026 |
| Nappicycle Cymru Ltd | Water & waste | 2024 |
| Nappicycle Ltd | Water & waste | 2011 |
| Nathan Davies Engineering Ltd | Professional & scientific | 2008 |
| Natty Bar Limited | Hospitality | 2024 |
| Natur Cymru Ltd. | Extraterritorial | 2005 |
| Natural Environmental Engineering Ltd | Manufacturing | 2024 |
| Natural Environmental Ltd | Manufacturing | 2011 |