| Medizom Limited | Education | 2024 |
| Medpotens Limited | Manufacturing | 2017 |
| Medpsych Care Limited | Health & social care | 2015 |
| Medtech Accelerator Limited | Professional & scientific | 2016 |
| Medtech International Limited | Professional & scientific | 2010 |
| Meduc Limited | Education | 2018 |
| Meduri Homes Limited | Real estate | 2021 |
| Medwood Limited | Health & social care | 2001 |
| Medyo Ltd | Manufacturing | 2023 |
| Meemaprop Limited | Real estate | 2021 |
| Meera Ravi Consultancy Ltd | Health & social care | 2019 |
| Meet Cambridge Limited | Other services | 2016 |
| MEG Facilities Management Limited | Construction | 2017 |
| Mega Chance Trading Limited | Extraterritorial | 2015 |
| Mega Magpie Limited | Wholesale & retail | 2021 |
| Mega Property Management Ltd | Real estate | 2020 |
| Megadodo Technical Services Ltd | Professional & scientific | 2025 |
| Megagvm Ltd | Manufacturing | 2025 |
| Megahertz Technologies Limited | Information & communication | 2014 |
| Megalink Industry Company Limited | Administrative & support | 2020 |
| Megamossa Ltd. | Manufacturing | 2021 |
| Megan Jones Limited | Health & social care | 2020 |
| Megarobo Technologies (UK) Limited | Financial services | 2022 |
| Megha Traders Ltd | Wholesale & retail | 2016 |
| Megmill Holdings Ltd | Real estate | 2018 |
| Megnajet Ltd | Other services | 2010 |
| Mego UK Limited | Hospitality | 2015 |
| Mehfil Works Ltd | Other services | 2025 |
| Mehmet Ozcan Hairdresser Ltd | Other services | 2021 |
| Meiamhoy Limited | Professional & scientific | 2024 |
| Meishu Ceroplastic Co., Ltd | Wholesale & retail | 2017 |
| Meiyang Electrical Co., Ltd | Extraterritorial | 2019 |
| Meken Growth and Market Ltd | Information & communication | 2026 |
| Melanie Hopper Limited | Health & social care | 2017 |
| Melanmead Limited | Real estate | 1973 |
| Melanoma Focus | Health & social care | 2007 |
| Melbourn Farms Holdings Limited | Financial services | 2024 |
| Meldire Limited | Real estate | 1968 |
| Meligraphics Limited | Information & communication | 2016 |
| Meliha Limited | Hospitality | 2022 |
| Melissa Family Ltd | Professional & scientific | 2023 |
| Melivera Ltd | Information & communication | 2026 |
| Mellor Cardiology LLP | | 2021 |
| Melobi Limited | Health & social care | 1999 |
| Melomarket Ltd | Administrative & support | 2023 |
| Melsin Medical Co., Ltd | Extraterritorial | 2018 |
| Melton House Limited | Professional & scientific | 2014 |
| Melton Manor (Melton Mowbray) Residents Company Limited | Households | 2019 |
| Membrinet Maintenance Services Ltd | Manufacturing | 2024 |
| Memorable Domains Ltd | Information & communication | 2010 |
| Memorify Technologies Limited | Information & communication | 2024 |
| Menagerie Theatre Company | Arts & recreation | 2001 |
| Mendimage Ltd | Health & social care | 2024 |
| Mendu AI Ltd | Real estate | 2025 |
| Menelaus Maths Ltd | Information & communication | 2018 |
| Meng Trading Limited | Wholesale & retail | 2021 |
| Mengkou International Brand Management Co., Ltd | Wholesale & retail | 2025 |
| Mentizo Limited | Information & communication | 2013 |
| Menzies Holdings Ltd | Financial services | 2026 |
| Menzies Ventures Ltd | Construction | 2022 |
| Mepro Cosmetic Ltd | Wholesale & retail | 2018 |
| Mercer Show Team Ltd | Agriculture & fishing | 2025 |
| Merchants of Light Ltd | Information & communication | 2014 |
| Merchants' Quarter Management Limited | Real estate | 2007 |
| Mercier and Thom Limited | Manufacturing | 2024 |
| Mercurial Pictures Limited | Information & communication | 2014 |
| Mere Solutions Limited | Information & communication | 2019 |
| Meridian (Hampton Hargate) Management Company Limited | Real estate | 2008 |
| Meridian and Eastern Limited | Health & social care | 2018 |
| Meridian Civil Engineering Ltd | Professional & scientific | 2021 |
| Meridian Data Intelligence Limited | Information & communication | 2026 |
| Meridian Golf Limited | Arts & recreation | 2025 |
| Meridian Impact CIC | Education | 2021 |
| Meridian Life Limited | Extraterritorial | 2005 |
| Meridian PCN Ltd | Health & social care | 2021 |
| Meridian Way Management Company Limited | Real estate | 2019 |
| Merlan Sky Aviation Ltd | Manufacturing | 2026 |
| Merlin Aviation Art Limited | Wholesale & retail | 2016 |
| Merlin Developments (Cambridge) Limited | Construction | 2010 |
| Merlo Trade Co., Ltd | Wholesale & retail | 2025 |
| Merosity Ltd | Wholesale & retail | 2022 |
| Merreloak Limited | Construction | 1990 |
| Merrialjane Ltd | Administrative & support | 2024 |
| Merrick Limited | Real estate | 1995 |
| Merriments Gardens Limited | Wholesale & retail | 2017 |
| Merrington Place Management Company Ltd | Households | 2010 |
| Merryberkeley Care Limited | Health & social care | 2026 |
| Merrycare 2 Limited | Real estate | 2022 |
| Merrycare Investments Limited | Real estate | 2015 |
| Merrycare Limited | Health & social care | 2005 |
| Mertec Design Limited | Manufacturing | 2023 |
| Merton Dairy Ltd | Agriculture & fishing | 2019 |
| Mesa-Tech Ltd | Professional & scientific | 2020 |
| Mesden Plastic Products Co., Limited | Manufacturing | 2020 |
| Mesh Structure Living Ltd | Construction | 2025 |
| Mesolens Limited | Manufacturing | 2009 |
| Messara Ltd | Wholesale & retail | 2025 |
| Messrs J S & K W Burgess LP | | 2025 |
| Metacullis Ltd | Professional & scientific | 2026 |
| Metail Limited | Information & communication | 2007 |