| Mcalister & Co Insolvency Practitioners Limited | Financial services | 2007 |
| Mccartan Group Ltd | Real estate | 2023 |
| Mccarthy & Co Contractors Ltd | Construction | 2025 |
| Mccarthy Electrical Services Ltd | Manufacturing | 2021 |
| Mccarthy-James Crofty Inn Ltd | Hospitality | 2024 |
| MCE Substation Services Ltd | Manufacturing | 2026 |
| Mchatton Properties Ltd | Real estate | 2019 |
| Mckernaninteriors Ltd | Construction | 2022 |
| Mcmp Investment Ltd | Real estate | 2022 |
| Mcog Properties Ltd | Real estate | 2023 |
| Mcqueen Consulting Limited | Professional & scientific | 2024 |
| Mcqueen Tyres Ltd | Wholesale & retail | 2025 |
| MCR Logistics Ltd | Professional & scientific | 2025 |
| MCU Consultancy Limited | Professional & scientific | 2024 |
| MCZ Sales Ltd | Wholesale & retail | 2025 |
| MD Carpentry Ltd | Construction | 2015 |
| MD Communicationz Ltd | Wholesale & retail | 2020 |
| MD Cranes Ltd | Professional & scientific | 2025 |
| MD Engineering Limited | Professional & scientific | 2025 |
| MD Home Maintenance Ltd Ltd | Administrative & support | 2003 |
| MD Quality Management Ltd | Professional & scientific | 2024 |
| MD Surgical Ltd | Health & social care | 2013 |
| MD Survey Services Limited | Professional & scientific | 2024 |
| MDC Construction Limited | Construction | 2013 |
| MDC Heating Services Ltd | Manufacturing | 2003 |
| Mdell Installations Ltd | Construction | 2026 |
| MDI Hair Ltd | Real estate | 2024 |
| Mdjlets Limited | Hospitality | 2024 |
| Mdjw Consulting Ltd | Professional & scientific | 2022 |
| Mdlp Ltd | Administrative & support | 2025 |
| MDN Stucco Veneziano Ltd | Construction | 2024 |
| Mdow Ltd | Financial services | 2019 |
| Mdzf Bodyshop Ltd | Wholesale & retail | 2012 |
| Mdzn Ltd | Health & social care | 2023 |
| Mead Services Limited | Construction | 2003 |
| Meadow Fish Bar Limited | Hospitality | 2017 |
| Meadow Street Motors Limited | Wholesale & retail | 1995 |
| Meadow View Country Estates Limited | Real estate | 2014 |
| Meadow View Sports Development Ltd | Arts & recreation | 2014 |
| Meadow Ways Farm Limited | Agriculture & fishing | 2016 |
| Meadowdown Limited | Professional & scientific | 2021 |
| Meanz PCM Construction Consultancy Ltd | Construction | 2020 |
| Meat and Greek Barry Limited | Hospitality | 2020 |
| Meat and Greek Ltd | Hospitality | 2014 |
| Meat and Greek Newport Limited | Hospitality | 2022 |
| Meat Matters Limited | Wholesale & retail | 2019 |
| MEB Legal Consulting Services Limited | Professional & scientific | 2024 |
| Mecanicteodor Ltd | Wholesale & retail | 2026 |
| Mech Rail SW Ltd | Manufacturing | 2022 |
| MED Diner Swansea Ltd | Hospitality | 2023 |
| MED Team Primary Care Services Limited | Administrative & support | 2008 |
| Med-Co (Europe) Ltd | Administrative & support | 2000 |
| Med-Co Group Ltd | Financial services | 2017 |
| Med-Co Healthcare Services Ltd | Health & social care | 2017 |
| Med-Co Secure Healthcare Services Ltd | Health & social care | 2010 |
| Med-Co Staffing Ltd | Administrative & support | 2017 |
| Medcare UK International Staffing Solutions Ltd | Administrative & support | 2025 |
| Meddyg Antur Ltd | Education | 2022 |
| Media G CYF | Information & communication | 2013 |
| Media Mastery Ltd | Arts & recreation | 2025 |
| Medicair Ltd | Wholesale & retail | 2020 |
| Medical Murph Limited | Health & social care | 2019 |
| Medical Weight Management Clinic Limited | Health & social care | 2025 |
| Medicat Limited | Administrative & support | 1998 |
| Medics Without Borders Limited | Health & social care | 2022 |
| Medigig Health Care Services Ltd | Health & social care | 2021 |
| Mediquip Solutions Limited | Transport & logistics | 2020 |
| Mediterranean Diners Limited | Hospitality | 2022 |
| Medix Solutions Ltd | Health & social care | 2015 |
| Medra Aesthetics Ltd | Other services | 2025 |
| Medrock Limited | Health & social care | 2025 |
| Medshaw Limited | Real estate | 2012 |
| Medteam Healthcare Limited | Administrative & support | 2015 |
| Medusa Collective Ltd | Arts & recreation | 2025 |
| Medusa’S Tattoos & Piercings Ltd | Arts & recreation | 2020 |
| Medwin Ltd | Construction | 2020 |
| Meer Labs Limited | Information & communication | 2022 |
| Meer Sons Limited | Wholesale & retail | 2024 |
| Megafam Media Ltd | Professional & scientific | 2019 |
| Megan and Claude Limited | Other services | 2017 |
| Megatrix Consultancy Ltd | Information & communication | 2018 |
| Meithrinfa Joio Day Nursery Ltd | Health & social care | 2021 |
| MEJ Social Care Limited | Health & social care | 2015 |
| MEL & Norik Properties Ltd | Real estate | 2025 |
| Mel's Helping Hands CIC | Administrative & support | 2025 |
| Melin Energy Consultants Limited | Administrative & support | 2007 |
| Melin Tybie Properties Ltd | Real estate | 2015 |
| Meliora Pubs Ltd | Hospitality | 2022 |
| Melius Holdings Limited | Financial services | 2018 |
| Mellin Associates Limited | Arts & recreation | 2023 |
| Memo Morriston Ltd | Hospitality | 2024 |
| Mens Formal Hire Limited | Wholesale & retail | 2014 |
| Mental Health Swims CIC | Other services | 2020 |
| Menter Afon Limited | Manufacturing | 2024 |
| Menter Iaith Castell Nedd Port Talbot | Arts & recreation | 2007 |
| Mentrus Developments Limited | Construction | 2009 |
| Menu Collective Ltd | Hospitality | 2021 |
| Menu Priced Accountants Ltd | Professional & scientific | 2018 |
| Menu Priced Accounting Limited | Extraterritorial | 2015 |
| MEO Estates Ltd | Real estate | 2019 |