| MDG Enterprises Limited | Construction | 2015 |
| MDL Home Improvements Ltd | Construction | 2021 |
| Mdrw Limited | Real estate | 2017 |
| MDS Transform Ltd | Information & communication | 2025 |
| Meacan Civils Ltd | Other services | 2026 |
| Meadhold Limited | Financial services | 2000 |
| Meadow Car Sales Limited | Wholesale & retail | 2023 |
| Meadow Farm Lincs Limited | Real estate | 2025 |
| Meadow Fresh Hampton Ltd | Wholesale & retail | 2022 |
| Meadow Homes and Land Ltd | Other services | 2025 |
| Meadows Care Group Ltd | Health & social care | 2026 |
| Meadows Care Home Limited | Extraterritorial | 2015 |
| Meads TCG Collectibles & Emporium Ltd | Wholesale & retail | 2026 |
| Measures Farms Limited | Agriculture & fishing | 1948 |
| Meatshopdrop Ltd | Wholesale & retail | 2020 |
| Mebs Investment Limited | Real estate | 2026 |
| Mebs Motors Ltd | Wholesale & retail | 2024 |
| Mebtronic Ltd | Wholesale & retail | 2019 |
| MEC Peterborough Ltd | Construction | 2026 |
| MED Finders Ltd | Health & social care | 2021 |
| Medesham Homes LLP | | 2016 |
| Medesham Limited | Hospitality | 2017 |
| Medesham Properties LLP | | 2018 |
| Media Outcomes Limited | Professional & scientific | 2001 |
| Mediate Technology Limited | Information & communication | 2013 |
| Medibex Limited | Professional & scientific | 2013 |
| Medicaid Action Limited | Health & social care | 2009 |
| Medical Apothecary Solutions Ltd | Health & social care | 2022 |
| Medical Safety Holdings Limited | Financial services | 2026 |
| Medical Safety Solutions Limited | Professional & scientific | 2005 |
| Medical Supply Wholesale Ltd | Wholesale & retail | 2023 |
| Medicmart Ambulance Service Limited | Transport & logistics | 2017 |
| MEDICS24/7 Ltd | Health & social care | 2015 |
| Medicspring Ltd | Health & social care | 2022 |
| Medikuest Limited | Health & social care | 2023 |
| Medras Consultants Ltd | Professional & scientific | 2022 |
| Meds Pharma Ltd | Wholesale & retail | 2017 |
| Medusa Live Limited | Arts & recreation | 2018 |
| Medusa Vision Ltd | Information & communication | 2018 |
| Medyann Limited | Construction | 2017 |
| MEE Growers Ltd | Agriculture & fishing | 2009 |
| Meem Zari Ltd | Manufacturing | 2025 |
| Mees Pharma Ltd | Health & social care | 2025 |
| Mefco Ltd | Hospitality | 2012 |
| Mega Car Shop Ltd | Wholesale & retail | 2012 |
| Mega Home Furniture Ltd | Wholesale & retail | 2023 |
| Mega Promocial Ltd | Wholesale & retail | 2022 |
| Mel's Developments Limited | Real estate | 2018 |
| Melanie Richard's Hair Boutique Limited | Other services | 2012 |
| Melia Treasures Ltd | Wholesale & retail | 2023 |
| Melinkunim Group Ltd | Health & social care | 2018 |
| Melium Consulting Limited | Administrative & support | 2016 |
| Mellows Projects Limited | Construction | 2015 |
| Melman Soft Ltd | Information & communication | 2025 |
| Melo Tone Limited | Information & communication | 2026 |
| Melodic Link Limited | Information & communication | 2021 |
| Melora Ltd | Other services | 2015 |
| Melrose Glen (Contracts) Limited | Professional & scientific | 2010 |
| Melrose Health Care Limited | Public administration | 2022 |
| Meltcrox Limited | Financial services | 2008 |
| Meltec Electrical Ltd | Construction | 2025 |
| Meltis House Limited | Real estate | 2022 |
| Melton Beauty Packaging Ltd | Professional & scientific | 2020 |
| Melvman Enterprise Limited | Health & social care | 2024 |
| Meme's Services Ltd | Health & social care | 2015 |
| Memento Holdings Ltd | Financial services | 2022 |
| Memox Ltd | Wholesale & retail | 2023 |
| MEN of Power Ltd | Transport & logistics | 2025 |
| Menai Holdings Ltd | Financial services | 2018 |
| Mencap Limited | Health & social care | 1966 |
| Mencap Pension Trustee Limited | Financial services | 2019 |
| Mende's Ventures Ltd | Water & waste | 2019 |
| Mental Health in the Workplace Ltd | Professional & scientific | 2024 |
| Mental Health Solutions + Limited | Health & social care | 2017 |
| Mental Wellness Counselling Ltd | Health & social care | 2023 |
| Mentign Ltd | Information & communication | 2025 |
| Mepal P.O. & Stores Ltd | Wholesale & retail | 2010 |
| Mepho Limited | Health & social care | 2020 |
| MER Properties Management Ltd | Real estate | 2023 |
| Merani Zaxo Ltd | Other services | 2026 |
| Meratix Ltd | Information & communication | 2026 |
| Mercedes Dias Beauty Artist Ltd | Other services | 2025 |
| Mercedony Homes Limited | Health & social care | 2025 |
| Merchmix Inc Limited | Information & communication | 2025 |
| Mercuri Consultants Limited | Financial services | 2015 |
| Mercurial Minds (PVT) Limited | Information & communication | 2020 |
| Mercurial Minds Global Limited | Information & communication | 2019 |
| Mercury Refurbishments Ltd | Construction | 2025 |
| Meremouth Farm Limited | Agriculture & fishing | 2023 |
| Mereside Developments Limited | Real estate | 2006 |
| Meridian Close Bluntisham Management Company Limited | Households | 2020 |
| Meridian Employment Ltd | Administrative & support | 2023 |
| Meridian Estates Group Ltd | Real estate | 2025 |
| Meridian Sales Leadership Limited | Professional & scientific | 2025 |
| Meridian Transformation Group Ltd | Professional & scientific | 2026 |
| Merl Developments Ltd | Construction | 2025 |
| Merl Lettings Limited | Real estate | 2025 |
| Merlin 2014 Limited | Construction | 2014 |
| Merlin Builders and Developments Limited | Construction | 2021 |
| Merlin Industries International Limited | Construction | 1994 |