| MDH Readymix Ltd | Manufacturing | 2018 |
| MDH Recycling Ltd | Water & waste | 2022 |
| Mechanical Fitout Ltd | Energy | 2013 |
| MED Online Marketing Solutions Ltd | Professional & scientific | 2026 |
| MED Online Selling Solutions Ltd | Wholesale & retail | 2026 |
| Medayo Limited | Information & communication | 2017 |
| Medi.Tate Health Consultancy Ltd | Health & social care | 2024 |
| Media Symphonics Limited | Information & communication | 2003 |
| MEDIC4 Limited | Health & social care | 2012 |
| Medical Negligence Solicitors Direct Ltd | Professional & scientific | 2026 |
| Medical Revision Ltd | Professional & scientific | 2016 |
| Medicine Independante Limited | Health & social care | 2025 |
| Medico Legal Assistance Limited | Professional & scientific | 2011 |
| Medlinx Limited | Administrative & support | 2008 |
| Medman Limited | Real estate | 2014 |
| Medusa Gems Limited | Wholesale & retail | 2017 |
| Megabyte Computer Services Limited | Other services | 2001 |
| Megantic Services Limited | Information & communication | 1996 |
| Meggi Salon Ltd | Other services | 2024 |
| Megruc Property Investments Limited | Real estate | 2019 |
| Mehmet Turkish Kitchen Ltd | Hospitality | 2025 |
| Mehta Wholesale Ltd | Wholesale & retail | 2024 |
| Melbry Ltd | Information & communication | 2026 |
| Melford Construction Limited | Construction | 2000 |
| Melia Hair Limited | Other services | 2024 |
| Meliora Care Services Ltd | Health & social care | 2024 |
| Meliora Learning Ltd | Education | 2026 |
| Melling Road Ltd | Construction | 2025 |
| Melton Grange RTM Company Ltd | Households | 2025 |
| Melville Flats Limited | Hospitality | 1975 |
| Members Discounts UK Limited | Professional & scientific | 2021 |
| Mendo Design Ltd | Administrative & support | 2020 |
| Menogi Ltd | Wholesale & retail | 2024 |
| Menray Limited | Information & communication | 2023 |
| Mentha Inspections Ltd | Professional & scientific | 2019 |
| Meols Hall Events Limited | Hospitality | 1994 |
| Meraki Chocolate Limited | Manufacturing | 2018 |
| Merchant House Interim Ltd | Administrative & support | 2016 |
| Merchants Print & Design Limited | Manufacturing | 2024 |
| Mercury Aircraft Interiors Limited | Administrative & support | 2020 |
| Meredith Financial Services Ltd | Financial services | 2022 |
| Meridian Developments (S.P.) Limited | Real estate | 2003 |
| Merriman Health Limited | Health & social care | 2020 |
| Mersey Control System Limited | Professional & scientific | 2015 |
| Mersey Towel Linen Ltd | Other services | 2014 |
| Mersey Vend & Property Ltd | Wholesale & retail | 2022 |
| Merseydrive Ltd | Education | 2022 |
| Merton Towers Management Limited | Households | 1984 |
| Metin Food Limited | Hospitality | 2019 |
| Metrosol Limited | Manufacturing | 1991 |
| MFA Repairs and Maintenance Ltd | Construction | 2024 |
| Mfair Services Limited | Manufacturing | 2018 |
| Mfeb Engineering Ltd | Construction | 2016 |
| MG Carpentry and Building Limited | Construction | 2022 |
| MG Elite Estates Ltd | Real estate | 2025 |
| MG Facade Fixing Ltd | Construction | 2015 |
| Mg.Moses Haulage Limited Ltd | Transport & logistics | 2018 |
| MH Trinity Services Ltd | Construction | 2014 |
| MHJ Properties Ltd | Households | 2019 |
| MIA Ironing Ltd | Administrative & support | 2025 |
| Mia's Dog Shop Ltd | Wholesale & retail | 2023 |
| Michael Coyne Transport Limited | Wholesale & retail | 2006 |
| Michael Healy Limited | Professional & scientific | 2009 |
| Michael John Academy Limited | Education | 2011 |
| Michael Jones Ltd | Professional & scientific | 2011 |
| Michael Lowe Trustees Limited | Professional & scientific | 2014 |
| Michael Lynch Logistics Limited | Transport & logistics | 2009 |
| Michell Computing Limited | Information & communication | 2017 |
| Michell's Limited | Professional & scientific | 2013 |
| Michelle Mortimer Cosmetics Limited | Health & social care | 2014 |
| Mickey's Wholesome Emporium Limited | Wholesale & retail | 2025 |
| Miclar Limited | Administrative & support | 2003 |
| Microgen Energy Ltd | Professional & scientific | 2015 |
| Middlehurst Property Development Limited | Real estate | 2021 |
| Middletonrigby Ltd | Construction | 2019 |
| Midplant Limited | Health & social care | 1985 |
| Mifh Limited | Professional & scientific | 2002 |
| Migastown Limited | Transport & logistics | 2013 |
| Migem Limited | Financial services | 2015 |
| Miggy Ltd. | Administrative & support | 2015 |
| Mighty Radio Leeds Ltd | Information & communication | 2020 |
| Mighty Radio Ltd. | Information & communication | 2013 |
| Mike Doyle Electrical Solutions Limited | Construction | 2017 |
| Mike Kidd (Horse Power) Ltd | Arts & recreation | 2008 |
| Miketash Limited | Health & social care | 2019 |
| Mikhail Contract Interiors Limited | Construction | 2020 |
| Mikhail Darts Management Limited | Professional & scientific | 2025 |
| Mikhail Hotels and Leisure Holdings Limited | Hospitality | 2016 |
| Mikhail Hotels Limited | Hospitality | 2015 |
| Mikhail PUB Group Limited | Financial services | 2025 |
| Mikinteriors Limited | Professional & scientific | 2024 |
| Milan Building Services Ltd | Construction | 2003 |
| Miles & Roberts Ltd | Hospitality | 2022 |
| Milford Wealth Management Limited | Financial services | 2014 |
| Milkie Bar Limited | Wholesale & retail | 2022 |
| Milla Cosmetics UK Limited | Other services | 2020 |
| Millars ARK Toys Limited | Wholesale & retail | 1958 |
| Millars Pace Limited | Real estate | 2019 |
| Millen Capital Partners LLP | | 2010 |
| Millennial Scaffolding Ltd | Construction | 2018 |