| MAY4 Property Ltd | Real estate | 2020 |
| MB Dance Centre Ltd | Education | 2020 |
| Mbonfiglio Limited | Wholesale & retail | 2022 |
| MBP Coaching Ltd | Arts & recreation | 2023 |
| Mccall Property Management Ltd | Real estate | 2025 |
| Mccarthy Utilities Limited | Construction | 2019 |
| Mcclune Holdings Ltd | Real estate | 2025 |
| Mcclure's Funeral Service Limited | Other services | 2016 |
| Mccready Footwear Limited | Wholesale & retail | 2007 |
| Mccready Holdings Limited | Other services | 1996 |
| Mccullagh Pharma Consulting Ltd | Professional & scientific | 2026 |
| Mcguinness Metals and Waste Recycling Limited | Wholesale & retail | 2014 |
| Mchare Limited | Hospitality | 1974 |
| Mcintosh Construction UK Limited | Construction | 2016 |
| Mckenna Inns Ltd | Hospitality | 2026 |
| Mckibben Property Limited | Real estate | 2026 |
| MCM Robotics Ltd | Information & communication | 2023 |
| Mcml Holdings Ltd | Financial services | 2026 |
| Mcmullon Limited | Professional & scientific | 2022 |
| MCS Haulage Limited | Transport & logistics | 2011 |
| MCT Inns Limited | Hospitality | 2023 |
| Mcvay Asset Management Limited | Financial services | 2026 |
| MD Property Packaging Ltd | Real estate | 2026 |
| MD Vehicle and Property Trading Ltd | Wholesale & retail | 2024 |
| MDL Leisure Ltd | Hospitality | 2025 |
| Meaco Measurement & Control Limited | Manufacturing | 2008 |
| Meallua Limited | Manufacturing | 2025 |
| Mechwise Services Ltd | Construction | 2023 |
| Med-Arb-International Limited | Professional & scientific | 2024 |
| Medchemica Consultancy Limited | Health & social care | 2013 |
| Medchemica Limited | Health & social care | 2012 |
| Medic OJO Ltd | Health & social care | 2022 |
| Medical Doorway Limited | Education | 2015 |
| MEDICALD4 Limited | Health & social care | 2022 |
| Meditank Limited | Information & communication | 2013 |
| Mediterranean Investment Properties LLP | | 2003 |
| Meel Group (Building Services) Limited | Construction | 2001 |
| Meel Group (Projects) Limited | Construction | 1964 |
| Meeson Kitchens & Bedrooms Ltd | Construction | 2023 |
| Mehmetz Barbers Ltd | Other services | 2026 |
| Meleki Investments Limited | Information & communication | 1988 |
| Melexim Holdings Limited | Wholesale & retail | 2018 |
| Mellards Bar Limited | Hospitality | 2016 |
| Melltray Property Ltd | Real estate | 2022 |
| Melrone Developments Limited | Real estate | 2002 |
| MEN Unite C.I.C | Health & social care | 2019 |
| Mental Health Organisation Limited | Education | 2020 |
| Mental Strength Clothing Limited | Wholesale & retail | 2024 |
| Mere Court (Alsager) Management Company Limited | Households | 1973 |
| Mere House Estates Limited | Households | 2002 |
| Mere Retreats Limited | Hospitality | 2025 |
| Merson Technology Limited | Information & communication | 2012 |
| Meryland Transport Ltd | Transport & logistics | 2025 |
| Metal Fabrication Systems Limited | Manufacturing | 2004 |
| Meteor Business Consultancy Ltd | Professional & scientific | 2014 |
| Metro Shops Limited | Wholesale & retail | 2025 |
| Metrobond Limited | Professional & scientific | 2013 |
| MFS Industrial Solutions Ltd | Education | 2021 |
| MGW Automotive Ltd | Wholesale & retail | 2024 |
| MH Authoring Ltd | Information & communication | 2025 |
| MHC Flats Ltd | Real estate | 2023 |
| MHS Holdings Ltd | Financial services | 2026 |
| MI Legacy Suites Limited | Households | 2026 |
| MI Projects (UK) Limited | Construction | 2014 |
| Michael F Curran Limited | Professional & scientific | 2024 |
| Michael Morgan Studio Ltd | Professional & scientific | 2026 |
| Michael Spedition Limited | Transport & logistics | 2019 |
| Microprise Limited | Manufacturing | 1990 |
| MID N.I. Ltd | Financial services | 2026 |
| Midland GAS Services Ltd | Other services | 2003 |
| Midlands Breast Radiology Services Ltd | Health & social care | 2021 |
| Midlands Technologies Limited | Administrative & support | 2019 |
| Midway Holdings (Staffs) Ltd | Real estate | 2021 |
| Mika Ltd | Real estate | 2024 |
| Mile Actuarial Ltd | Financial services | 2025 |
| Mile Equine Limited | Agriculture & fishing | 2025 |
| Mile Property Limited | Real estate | 2025 |
| Mill House Accountancy Limited | Professional & scientific | 2011 |
| Millennium Global Consultancy Ltd | Administrative & support | 2024 |
| Miller Residential Ltd | Real estate | 2025 |
| Millers Green (Shelfield Drive) NO 2 Management Limited | Households | 2005 |
| Milton Non-Ferrous Casting Co. Limited | Manufacturing | 1963 |
| Miltons (Chemists) Limited | Wholesale & retail | 1942 |
| Milvus Brook Holdings LLP | | 2024 |
| Milvus Brook Properties Limited | Real estate | 2018 |
| Mind Body Social Ltd | Education | 2025 |
| Mind Your Mate and Yourself (Mymy) | Health & social care | 2022 |
| MIND121 Limited | Health & social care | 2014 |
| Minerva Financial Solutions Limited | Financial services | 2022 |
| Ming-L.Co Ltd | Hospitality | 2024 |
| Mini Medics Ltd | Wholesale & retail | 2020 |
| Miradiology Limited | Health & social care | 2024 |
| Miru Properties Limited | Real estate | 2016 |
| Mishace Group Ltd | Administrative & support | 2023 |
| Miss Moco Ltd | Arts & recreation | 2014 |
| Miss PUB Group Ltd Ltd | Hospitality | 2024 |
| Mitchell-Beck Holdings Limited | Financial services | 2026 |
| Mitchell-Beck Limited | Construction | 2006 |
| MJ Social Work Consultancy Ltd | Professional & scientific | 2013 |
| MJ Watson Haulage Limited | Transport & logistics | 2017 |