| Mcalister Contracting Limited | Construction | 2024 |
| Mcarthur Murray Ltd | Professional & scientific | 2018 |
| MCB Capital Ltd | Households | 2022 |
| MCB Property Ltd | Construction | 2013 |
| Mcbride-Fletcher Consulting Limited | Health & social care | 2022 |
| Mcbrien Medical Writing Ltd | Professional & scientific | 2015 |
| Mccaul Cottage Ltd | Wholesale & retail | 2022 |
| Mcdiarmid Whitmore Limited | Administrative & support | 2014 |
| Mcewan Childcare Limited | Health & social care | 2007 |
| Mcfeal Ltd | Manufacturing | 2022 |
| MCG Cambridge Ltd | Hospitality | 2024 |
| Mcgrory Marketing Services Limited | Professional & scientific | 2020 |
| MCI Global Holding Ltd. | Wholesale & retail | 2023 |
| Mckenzie & Haywards Garage Ltd | Wholesale & retail | 2013 |
| Mckenzie Aero Ltd | Manufacturing | 2017 |
| Mckenzie Composite Contracting Ltd | Manufacturing | 2019 |
| Mckenzies Accounting & Advisory Services Limited | Professional & scientific | 2023 |
| Mckenzies Property Limited | Real estate | 2025 |
| Mckibbin Capital Ltd | Real estate | 2021 |
| Mckinnon Clinical Research Consulting Ltd | Professional & scientific | 2026 |
| MCLAREN0260 Ltd | Education | 2016 |
| Mcmahon Aviation Ltd | Manufacturing | 2026 |
| Mcmons Consulting Ltd | Information & communication | 2024 |
| Mcna DOT COM Limited | Information & communication | 2016 |
| Mcnulty Telecommunications Limited | Information & communication | 2018 |
| Mcsure Unique Ltd | Wholesale & retail | 2021 |
| MCT Research Ltd. | Information & communication | 2016 |
| MD Contracting and Farming Ltd | Agriculture & fishing | 2016 |
| MD Conversion Ltd | Manufacturing | 2024 |
| MD Cross Ltd | Health & social care | 2022 |
| MD Limited Company Ltd | Wholesale & retail | 2025 |
| MDA Limited Ltd | Wholesale & retail | 2026 |
| MDB Homes Limited | Construction | 2017 |
| MDC Aircraft Engineering Ltd | Manufacturing | 2022 |
| MDH Lighting Ltd | Extraterritorial | 2021 |
| MDH Technologies Ltd | Professional & scientific | 2025 |
| Mdhs Asbestos Consultants Limited | Professional & scientific | 2015 |
| MDL Investment Ltd | Real estate | 2025 |
| Mdmc Limited | Professional & scientific | 2026 |
| Mdrjk Limited | Construction | 2023 |
| MDS Business Ltd | Administrative & support | 2024 |
| Mead Construction (Cambridge) Limited | Construction | 2000 |
| Mead Groundworks Ltd | Professional & scientific | 2022 |
| Mead Homes Limited | Construction | 2011 |
| Mead Plant & Grab Ltd | Extraterritorial | 2018 |
| Meade House Management Company Limited | Households | 2012 |
| Meadow Farm Construction LLP | | 2024 |
| Meadow Park (ST Ives) Ltd | Real estate | 1990 |
| Meadow View Great Shelford Management Company Limited | Households | 2020 |
| Meadowbank, the Moor, Management Company Limited | Households | 2009 |
| Meadowcroft (Cambridge) Freehold Limited | Households | 2013 |
| Meadowlands (North) Limited | Households | 1967 |
| Meadowvelta Limited | Extraterritorial | 2000 |
| Meadowview R & S Limited | Financial services | 2022 |
| Meadspace Ltd | Information & communication | 2025 |
| Meaningful Careers Ltd | Administrative & support | 2023 |
| Means Solution Limited | Information & communication | 2023 |
| Meat Smoke Fire Limited | Wholesale & retail | 2014 |
| Meath Crescent London (UK) Ltd | Real estate | 2022 |
| Meatless Fast Food Limited | Hospitality | 2019 |
| Mebomine Limited | Information & communication | 2019 |
| Mebsuta Vermilion Limited | Wholesale & retail | 2025 |
| MEC Property Holdings Ltd | Real estate | 2014 |
| Mecapi Ltd | Manufacturing | 2026 |
| Mechango Ltd | Wholesale & retail | 2024 |
| Mechanica Marine and Maintenance Ltd | Manufacturing | 2024 |
| Mechanome BIO Ltd | Professional & scientific | 2025 |
| Mechapres Ltd | Professional & scientific | 2023 |
| Mechcam Limited | Professional & scientific | 2012 |
| Mechelec Automation Limited | Other services | 2014 |
| Mecklenburgh Square Limited | Real estate | 2020 |
| Meco UK and Ireland | Education | 1976 |
| Mecoo International Limited | Wholesale & retail | 2025 |
| Mecore Limited | Water & waste | 2016 |
| Mecpro Marine Ltd | Manufacturing | 2024 |
| MED ONC Professionals Limited | Administrative & support | 2016 |
| Med-Writeplus Ltd | Information & communication | 2020 |
| Medax Foundation Limited | Extraterritorial | 2025 |
| Medcam Healthcare Limited | Wholesale & retail | 2015 |
| Mededis Ltd | Professional & scientific | 2006 |
| Medeor LLP | | 2008 |
| Medeor Old Limited | Administrative & support | 2006 |
| Medeor Pharma Ltd | Professional & scientific | 2006 |
| Medev Solutions Ltd | Professional & scientific | 2016 |
| Medexchange Ltd | Health & social care | 2015 |
| Medha Health Care Limited | Health & social care | 2010 |
| Mediacarve Ltd | Information & communication | 2003 |
| Mediamerge Limited | Information & communication | 2006 |
| Mediatek Global Holdings Limited | Financial services | 2021 |
| Mediatek Research UK Limited | Information & communication | 2019 |
| Medical & Respiratory Services Limited | Health & social care | 2025 |
| Medical and More Limited | Information & communication | 2009 |
| Medical S G Limited | Health & social care | 2023 |
| Medicorp (Cambridge) Limited | Extraterritorial | 2010 |
| Medihub Limited | Information & communication | 2014 |
| Medimmune Limited | Professional & scientific | 1989 |
| Medissima Ltd | Health & social care | 2018 |
| Mediterranean Barbeque Limited | Hospitality | 2018 |
| Mediterranean Luxury Carpentry Ltd | Manufacturing | 2023 |
| Mediterranean Merguez Limited | Hospitality | 2019 |