| Lyonace Consulting Ltd | Professional & scientific | 2017 |
| LYP Betensh Ltd | Wholesale & retail | 2025 |
| Lyra Living Ltd | Real estate | 2020 |
| Lyra Strategy Group Limited | Professional & scientific | 2025 |
| Lyrem Limited | Professional & scientific | 2014 |
| Lyrical Kombat Limited | Information & communication | 2016 |
| Lyssons International Ltd | Financial services | 2019 |
| Lystajob Ltd | Information & communication | 2025 |
| Lyte Industries (Southern) Limited | | 1983 |
| LYU Seasons Limited | Arts & recreation | 2021 |
| Lyupet Express Ltd | Public administration | 2018 |
| LŪM Beauty Ltd | Wholesale & retail | 2025 |
| L’Argent Motivé Limited | Wholesale & retail | 2024 |
| L’Essence Mohsin Ltd | Wholesale & retail | 2025 |
| M & a Business Ltd | Real estate | 2016 |
| M & a Drylining Limited | Construction | 2017 |
| M & B Family Services Ltd | Information & communication | 2018 |
| M & B Hydraulics Limited | Manufacturing | 2001 |
| M & B Serviced Accommodations Ltd | Hospitality | 2025 |
| M & C Lewis LLP | | 2015 |
| M & E Procurement Ltd | Administrative & support | 2019 |
| M & H Hospitality Solutions Ltd | Wholesale & retail | 2012 |
| M & J Cosgrove Construction Limited | Construction | 1968 |
| M & J Transportation Ltd | Transport & logistics | 2019 |
| M & J Woods (NP) Ltd | Other services | 2019 |
| M & K Media Limited | Professional & scientific | 2026 |
| M & M Cardiff Ltd | Real estate | 2019 |
| M & M Fixings Ltd. | Wholesale & retail | 2010 |
| M & M Law (Caerphilly) Limited | Professional & scientific | 2026 |
| M & M Property (South Wales) Limited | Construction | 2024 |
| M & M Solicitors Limited | Professional & scientific | 2009 |
| M & M Speed Property Limited | Real estate | 2024 |
| M & M Speed Services Limited | Wholesale & retail | 2021 |
| M & N Property Investment Limited | Real estate | 2025 |
| M & N Rahman Limited | Hospitality | 2011 |
| M & O Foods Ltd | Hospitality | 2024 |
| M & R Contractors Limited | Construction | 2007 |
| M & R Import & Exporters Ltd | Wholesale & retail | 2019 |
| M & R Partners Consulting Limited | Financial services | 2024 |
| M & R Policing Academy and Constabulary Limited | Professional & scientific | 2016 |
| M & S Palmer Limited | Financial services | 2016 |
| M & S Properties Management Ltd | Real estate | 2021 |
| M & TC Consultants Limited | Arts & recreation | 2002 |
| M & Y News Agency Limited | Information & communication | 1999 |
| M a Autos Yorkshire Ltd | Wholesale & retail | 2021 |
| M a Construction Solutions Ltd | Construction | 2026 |
| M a Ezysource Ltd | Wholesale & retail | 2024 |
| M a Hale Ltd | Real estate | 2025 |
| M a Harvey Limited | Construction | 2002 |
| M a London Ltd | Hospitality | 2017 |
| M a Williams & Co Ltd | Wholesale & retail | 2021 |
| M and E Gambia Ltd | Transport & logistics | 2024 |
| M and M Garages (South Wales) Limited | Wholesale & retail | 2022 |
| M and S Cardiff Barbers Ltd | Other services | 2025 |
| M Brittain Consultancy Ltd | Information & communication | 2017 |
| M C Maritime Services Limited | Transport & logistics | 2020 |
| M C Page Implant Services Ltd | Health & social care | 2024 |
| M Camilleri Ltd | Health & social care | 2025 |
| M D Edwards Developments Limited | Real estate | 2004 |
| M D Lawrence Welding Services Limited | Construction | 2014 |
| M E S Electrical Services Limited | Construction | 2017 |
| M F Scenic Ltd | Construction | 2012 |
| M Faulkner Healthcare Ltd | Health & social care | 2022 |
| M Fisher Limited | Wholesale & retail | 2000 |
| M Francis (Cardiff) Limited | Administrative & support | 2014 |
| M G Mortgages Limited | Financial services | 2003 |
| M Green Insulation Ltd | Construction | 2024 |
| M H a Business Consultancy Services Ltd | Financial services | 2018 |
| M H Automation International Limited | Manufacturing | 1994 |
| M H Broadway Tyres Ltd | Wholesale & retail | 2026 |
| M H Car Sales Ltd | Wholesale & retail | 2026 |
| M Harris Healthcare Limited | Health & social care | 2019 |
| M I Business Solutions Limited | Administrative & support | 2006 |
| M I Enterprises Limited | Real estate | 2025 |
| M I Investments (London) Ltd | Real estate | 2024 |
| M J (Harrow) Ltd | Hospitality | 2018 |
| M J Griffiths Ltd | Financial services | 2023 |
| M J Hutchings Limited | Information & communication | 2007 |
| M J Practice Services Limited | Professional & scientific | 1997 |
| M J Purbrick Limited | Construction | 2006 |
| M J S Superstore Limited | Wholesale & retail | 2014 |
| M Jabiry Property Ltd | Real estate | 2019 |
| M Jahangir Bhutta Ltd | Wholesale & retail | 2025 |
| M Jones Holdings Limited | Financial services | 2024 |
| M K Alomar Ltd | Wholesale & retail | 2025 |
| M K Stores Limited | Wholesale & retail | 2015 |
| M M a Properties Ltd | Real estate | 2016 |
| M Maheson Ltd | Health & social care | 2010 |
| M Myers Driving School Ltd | Education | 2025 |
| M Norris Limited | Financial services | 2010 |
| M O'Neill Project Management Ltd | Construction | 2025 |
| M P Donnelly Properties Ltd | Real estate | 2020 |
| M Panahei Management Co Ltd | Financial services | 2018 |
| M Price International Limited | Construction | 2021 |
| M Price Production Limited | Construction | 2019 |
| M R 66 Limited | Hospitality | 2018 |
| M R M & Sons Building & Roofing Ltd | Construction | 2012 |
| M R S Electrical and Control Engineers Limited | Administrative & support | 1997 |
| M Raza & Co Ltd. | Professional & scientific | 2003 |
| M Roach Limited | Real estate | 2007 |