| Mason House (Management Company) Limited | Households | 2003 |
| Massam Coaching Limited | Other services | 2021 |
| Massey & Cross Ltd | Manufacturing | 2021 |
| Masters of Play Limited | Other services | 2021 |
| Mastertech Mobile Car Servicing & Repair Limited | Wholesale & retail | 2010 |
| Masuit Menswear Limited | Wholesale & retail | 2025 |
| MAT Sands Property Ltd | Real estate | 2026 |
| Mata Automotive UK Ltd | Manufacturing | 2016 |
| Matbco Ltd | Wholesale & retail | 2022 |
| Materra Systemic Labs Ltd | Professional & scientific | 2020 |
| Matrix Aviation Limited | Transport & logistics | 2002 |
| Matsaka Limited | Professional & scientific | 2024 |
| Matt J W Limited | Professional & scientific | 2014 |
| Matt Smith Construction Ltd | Construction | 2023 |
| Matthew Aldcroft Ltd | Water & waste | 2025 |
| Matthew Charles Business Consultancy Limited | Information & communication | 2023 |
| Matthew Goulding Logistics Ltd | Transport & logistics | 2022 |
| Mave 3.3 Consulting Limited | Professional & scientific | 2025 |
| Maverick Public House Ltd | Hospitality | 2020 |
| MAW Accountants Ltd | Professional & scientific | 2017 |
| MAX Bradshaw Coaching Ltd | Education | 2025 |
| MAX Detail Ltd | Wholesale & retail | 2022 |
| Maxiunit Property Management Limited | Households | 1987 |
| Maxtrust Ltd | Administrative & support | 2014 |
| Maycroft Dental Practice Ltd | Health & social care | 2025 |
| Mayern Media Ltd | Arts & recreation | 2026 |
| Mayhem Yachting Limited | Information & communication | 1999 |
| Mazgrab Limited | Construction | 2019 |
| MB (NW) Ltd | Wholesale & retail | 2021 |
| MB Neuro Ltd | Health & social care | 2025 |
| MB Sales Services Limited | Wholesale & retail | 2024 |
| MB Site Installation Services Ltd | Construction | 2021 |
| Mbnh Properties Ltd | Real estate | 2021 |
| Mbnlp Training & Consulting Limited | Professional & scientific | 2015 |
| MC Diagnostics Ltd | Manufacturing | 2006 |
| MC Echo Ltd | Administrative & support | 2020 |
| MC Garden & Pond Design Ltd | Administrative & support | 2024 |
| MC Property & Law Services Ltd | Real estate | 2004 |
| MCA (NW) Limited | Administrative & support | 2021 |
| MCA Security Services Ltd | Administrative & support | 2019 |
| Mcadam Roofing Limited | Construction | 2005 |
| MCB Consult Limited | Professional & scientific | 2025 |
| Mcconville Estates Ltd | Real estate | 2018 |
| Mcconville Holdings Ltd | Financial services | 2024 |
| Mccormick Investments Ltd | Professional & scientific | 2011 |
| Mccrellisbuildersnw Limited | Construction | 2025 |
| MCD Direct Ltd | Wholesale & retail | 2024 |
| MCD Holdings 2026 Ltd | Financial services | 2026 |
| Mcdermotts (Meols) Limited | Agriculture & fishing | 1950 |
| Mcdheere Property Ltd | Real estate | 2024 |
| Mcdonnell Marketing Limited | Real estate | 2025 |
| MCE. Electrical Contracts Limited | Construction | 2024 |
| Mcfeat Roofing Limited | Construction | 2023 |
| Mcgreal's Garden Supplies Limited | Wholesale & retail | 2022 |
| Mckane Properties (Commercial Leasehold) Limited | Real estate | 2023 |
| Mckane Properties (Commercial) Limited | Real estate | 2022 |
| Mckane Properties (Residential) Limited | Real estate | 2022 |
| Mckenna Services Limited | Administrative & support | 2024 |
| Mcker Limited | Real estate | 2014 |
| Mckhendo Properties Limited | Real estate | 2017 |
| Mclaughlin Construction Ltd | Construction | 2021 |
| MCM Security (NW) Limited | Administrative & support | 2022 |
| Mcmyles Ltd | Health & social care | 2019 |
| Mcnulty Property Limited | Real estate | 2022 |
| Mcrbg Limited | Hospitality | 2018 |
| Mcrobert Consultancy Limited | Education | 2025 |
| MD Baxter Ltd. | Health & social care | 2015 |
| MD Engineering (Wirral) Limited | Manufacturing | 2003 |
| MD Steel FAB Services Ltd | Construction | 2026 |
| MD Warranty Inspection Services Limited | Professional & scientific | 2004 |
| MD Warranty Support Services Limited | Professional & scientific | 2003 |
| MDA Wirral Limited | Construction | 1999 |
| MDG Live Limited | Arts & recreation | 2026 |
| MDI Recruitment + Logistics Ltd | Transport & logistics | 2021 |
| Mdjh Construction Services Limited | Administrative & support | 2009 |
| MDL 1875 Investments Ltd | Real estate | 2022 |
| MDM Digital Group Limited | Wholesale & retail | 2016 |
| MDT Consult Limited | Professional & scientific | 2015 |
| MDW Brickwork Ltd | Construction | 2023 |
| ME Again CIC | Health & social care | 2017 |
| Meadow House Holdings Ltd | Financial services | 2023 |
| Meaney-Tech Limited | Arts & recreation | 2024 |
| MEB Scaffolding Ltd | Construction | 2025 |
| MEC Homes Limited | Real estate | 2023 |
| Mechbox Ltd | Manufacturing | 2020 |
| Mechetric Services Limited | Manufacturing | 2007 |
| Mechspan Limited | Manufacturing | 2010 |
| Medex Solutions Limited | Health & social care | 2019 |
| Media Kynect Limited | Administrative & support | 2015 |
| Media Linkup Ltd | Other services | 2024 |
| Media Travel Insurance Services Ltd | Administrative & support | 2008 |
| Mediadvice Limited | Information & communication | 2010 |
| Medialith Studio Limited | Other services | 1979 |
| Medical Intelligence Group Ltd | Professional & scientific | 2020 |
| Medicine Crash Course Ltd | Education | 2020 |
| Medicolegal Reports Ltd | Health & social care | 2024 |
| Mediloc Ltd | Health & social care | 2022 |
| Medishock UK Limited | Manufacturing | 2021 |
| Mediterranean Bistro CH63 Ltd | Hospitality | 2026 |
| Medixs NW Ltd | Health & social care | 2021 |