| Materials Hive Limited | Wholesale & retail | 2025 |
| Matharu Interiors Ltd | Manufacturing | 2021 |
| Matharu Kitchen & Bedrooms Ltd | Manufacturing | 2021 |
| Mats Transport Limited | Transport & logistics | 2018 |
| Mattik Consultancy Services Ltd | Professional & scientific | 2022 |
| Mattu Services Ltd | Administrative & support | 2020 |
| Maven Air-Conditioning and Refrigeration Ltd | Construction | 2026 |
| Maverickks Ltd | Wholesale & retail | 2025 |
| Mavi Stores Ltd | Wholesale & retail | 2022 |
| MAX Automotive Group Ltd | Wholesale & retail | 2025 |
| MAX Car & Van Sales Ltd | Wholesale & retail | 2025 |
| MAX Fleetsupport Ltd | Wholesale & retail | 2020 |
| MAX Meals Ltd | Hospitality | 2025 |
| MAY Garden Limited | Hospitality | 2023 |
| Mayank Arora Ltd | Wholesale & retail | 2026 |
| Maydex Accounting Limited | Financial services | 2014 |
| Mayfair Compliance Group Limited | Professional & scientific | 2020 |
| Mayfair Management and Consultancy Limited | Administrative & support | 2023 |
| Mayswood Investments Ltd | Real estate | 2019 |
| Mbaya Millionaires Limited | Health & social care | 2021 |
| MBC Builders Ltd | Construction | 2025 |
| MBF Home Improvements Limited | Construction | 2012 |
| MBH Building Ltd | Construction | 2022 |
| MC Bricklaying & Building Services Limited | Construction | 2015 |
| MC the HAT Motor Club Limited | Wholesale & retail | 2003 |
| Mcarthur Shaun Limited | Wholesale & retail | 2017 |
| MCF Midlands Limited | Other services | 2018 |
| Mcghee SOT Limited | Wholesale & retail | 1997 |
| Mcgrath J Limited | Wholesale & retail | 2022 |
| Mckenzie Distribution Ltd | Wholesale & retail | 2020 |
| Mckeown R Limited | Wholesale & retail | 2024 |
| MCS Developments Ltd | Construction | 2018 |
| MCS Plant Hire Group Ltd | Administrative & support | 2018 |
| MCS Property Group Ltd | Transport & logistics | 2019 |
| MD Building Contractors Ltd | Construction | 2016 |
| MD Express Courier Service Ltd | Transport & logistics | 2020 |
| MD1 Distribution Ltd | Wholesale & retail | 2024 |
| MDH Property Group Limited | Real estate | 2018 |
| Mdoil Limited | Professional & scientific | 2004 |
| MDT Solutions/Services Ltd | Professional & scientific | 2019 |
| Meadowley Woodland Management Ltd. | Professional & scientific | 1990 |
| Meat Brothers Limited | Wholesale & retail | 2022 |
| Mechatronics Fabrication Limited | Information & communication | 2024 |
| Medical Expert Witness Alliance (Mewa) Limited Liability Partnership | | 2016 |
| Medical Experts Ltd | Health & social care | 2010 |
| Medical Project Management Limited | Professional & scientific | 1998 |
| Medina Domain Ltd | Real estate | 2020 |
| Medina Foods Ltd | Manufacturing | 2026 |
| Medina Meat Centre Ltd | Wholesale & retail | 2016 |
| Medina Pure Halal UK Ltd | Manufacturing | 2015 |
| Meer Corporation Limited | Information & communication | 2024 |
| Mega Source Ltd | Wholesale & retail | 2023 |
| Mehar Property Development Ltd | Real estate | 2025 |
| Mehar Transport Services Ltd | Transport & logistics | 2025 |
| Meharprints Ltd | Manufacturing | 2025 |
| Mehrdad Consulting Ltd | Professional & scientific | 2025 |
| Mehta Bains Property Holdings Limited | Real estate | 2026 |
| Meka Cleaning Services Ltd | Administrative & support | 2025 |
| Melap Singh & Co Ltd | Financial services | 2013 |
| Melike Wealth Ltd | Information & communication | 2024 |
| Melt ‘N Spread Ltd | Wholesale & retail | 2026 |
| Melus Locum Limited | Health & social care | 2014 |
| Menagwins Court Management Company Limited | Households | 2005 |
| Mendez Marketing Solutions Ltd | Professional & scientific | 2022 |
| Mendrew Ltd | Health & social care | 2023 |
| Mercatus Digitalis Ltd | Wholesale & retail | 2023 |
| Mercia Holdings Limited | Professional & scientific | 2017 |
| Mercia Property Holdings Limited | Construction | 2017 |
| Mercian Industrial Doors (East Midlands) Limited | Manufacturing | 1987 |
| Mercian Industrial Doors (South Wales) Limited | Construction | 2003 |
| Mercian Recycling Limited | Water & waste | 2003 |
| Mercian Shutters Limited | Construction | 1973 |
| Mercian Skip Hire Midlands Ltd | Water & waste | 2011 |
| Mercury GMG Limited | Information & communication | 2006 |
| Merits Cleaning Care UK Ltd | Administrative & support | 2026 |
| Merlinhill Finance Limited | Professional & scientific | 2025 |
| Merlinhill Holdings Limited | Professional & scientific | 2024 |
| Merlinhill Limited | Professional & scientific | 2025 |
| Messadjo Ltd | Health & social care | 2023 |
| Messy Mice Ltd | Other services | 2022 |
| Metagora Ltd | Information & communication | 2018 |
| Metalltechnik (UK) Limited | Wholesale & retail | 1991 |
| Metaltek International (UK) Limited | Financial services | 2008 |
| Metro Industrial Cleaning Limited | Other services | 2014 |
| Mfcc Limited | Construction | 2022 |
| MG Elite Enterprises Limited | Wholesale & retail | 2024 |
| MGH Card LLP | | 2015 |
| MGH Partner Company Limited | Real estate | 2015 |
| MGT Properties Ltd | Real estate | 2023 |
| MH Partners Ltd | Wholesale & retail | 2025 |
| MH Tiles Ltd | Wholesale & retail | 2020 |
| MHR Builders Limited | Construction | 2013 |
| Mhrj Luxury Limited | Wholesale & retail | 2023 |
| Miami Hot Ltd | Hospitality | 2025 |
| Michael Henry Transport Ltd | Manufacturing | 2023 |
| Michael Rutter Limited | Arts & recreation | 2007 |
| Michael Rutter Racing Limited | Arts & recreation | 2004 |
| Micmar Service Ltd | Transport & logistics | 2023 |
| Micrue Limited | Wholesale & retail | 2024 |
| Midland Bakeries Limited | Wholesale & retail | 2016 |