| Master Group PVT Ltd | Wholesale & retail | 2015 |
| Master of Arms Ltd | Wholesale & retail | 2015 |
| Master Planit Ltd | Professional & scientific | 2022 |
| Master Tech Autos Ltd | Wholesale & retail | 2009 |
| Materika Ltd | Construction | 2025 |
| Matertrans Ltd | Transport & logistics | 2019 |
| Mates Rates Catering Company Limited | Hospitality | 2026 |
| Mathews Luxury Travel Limited | Administrative & support | 2021 |
| Matt Dixon Electrical Limited | Construction | 2024 |
| Matthew Bright Limited | Construction | 2011 |
| Matthew LE Tissier Promotions Limited | Arts & recreation | 2005 |
| Mawsan Quest Ltd | Financial services | 2015 |
| Maxcontainersecurity Ltd | Administrative & support | 2024 |
| Maxsea UK Limited | Professional & scientific | 2026 |
| Maxwell Hair and Beauty Ltd | Other services | 2024 |
| Maxwell Retreats Ltd | Hospitality | 2025 |
| Maxxify Ltd | Wholesale & retail | 2019 |
| Maybush Pharmacy Limited | Wholesale & retail | 2025 |
| Mayne Trade Supplies Limited | Wholesale & retail | 1991 |
| Mazmac Limited | Construction | 2014 |
| MB Automation Build Ltd | Construction | 2021 |
| MB Nominees Limited | Professional & scientific | 1999 |
| MB Properties Private Limited | Real estate | 2024 |
| MB Propman Limited | Extraterritorial | 2005 |
| MB Secretaries Limited | Professional & scientific | 2003 |
| MB Signs Limited | Professional & scientific | 2013 |
| MBAR1 Limited | Professional & scientific | 2023 |
| Mbrady TM Ltd | Construction | 2024 |
| MC & R Roofing Ltd | Construction | 2019 |
| MC 503 Limited | Financial services | 2014 |
| Mcadam Scientific Ltd | Professional & scientific | 2018 |
| Mcandrew Bidco Ltd | Financial services | 2023 |
| Mcandrew Holdco Ltd | Financial services | 2023 |
| Mccaskie Software Consulting Limited | Information & communication | 2013 |
| MCG Consultancy Services Limited | Professional & scientific | 2002 |
| MCG MOT Services Ltd | Professional & scientific | 2023 |
| MCH Admin & Solutions Limited | Professional & scientific | 2013 |
| MCH Admin Limited | Professional & scientific | 2018 |
| MCI Electrical & Data Services Limited | Construction | 2009 |
| Mcih Limited | Financial services | 2017 |
| Mckinnon Roofing and Cladding Ltd | Construction | 2017 |
| MCM Catering Ltd | Hospitality | 2017 |
| Mcmanus Limited | Construction | 1986 |
| Mcneil Eyecare Ltd | Wholesale & retail | 2013 |
| Mcplant (Southern) Limited | Construction | 2005 |
| MCS Garage Services UK Limited | Wholesale & retail | 2007 |
| MD (Southern) Limited | Construction | 2022 |
| MD Truck and Trailer Spares Limited | Wholesale & retail | 2002 |
| MDC Advisory Limited | Professional & scientific | 2023 |
| Mdfellow Ltd | Information & communication | 2024 |
| MDL South Limited | Public administration | 2024 |
| MDS Productions Ltd | Arts & recreation | 2023 |
| MDY Tech Limited | Information & communication | 2022 |
| Meadham Ventures Limited | Other services | 2025 |
| MEADOW3 Limited | Agriculture & fishing | 2017 |
| Meadowbank Home Builders Limited | Construction | 2011 |
| Measure Events Ltd | Administrative & support | 2013 |
| MEC Contracting Services Ltd | Administrative & support | 2026 |
| Med-Tech Data & Marketing Limited | Professional & scientific | 2024 |
| Medaris Ltd | Manufacturing | 2025 |
| Medatech UK Limited | Information & communication | 2001 |
| Medbillelite Limited | Administrative & support | 2025 |
| Medibuild Limited | Construction | 1997 |
| Medical-Secretary Limited | Administrative & support | 2025 |
| Medicot Limited | Education | 1998 |
| Medilogic UK Limited | Information & communication | 2005 |
| Medis Dent Limited | Health & social care | 2013 |
| Medjool Media Ltd | Professional & scientific | 2024 |
| Medmerry Services Ltd | Construction | 2023 |
| Medusa Beauty Ltd | Other services | 2024 |
| Meena Machina Limited | Information & communication | 2017 |
| Meikle Property Partnership LLP | | 2021 |
| Mellfields Limited | Transport & logistics | 1982 |
| Mellow Fish Ltd | Information & communication | 2007 |
| Melwood Construction Limited | Construction | 2019 |
| Memory & Batho Brickwork & Landscape Contractors Ltd | Construction | 2017 |
| Meonmarsh Ltd | Administrative & support | 2019 |
| Mercer Clinical Services Limited | Professional & scientific | 2025 |
| Merchant Design Limited | Administrative & support | 1984 |
| Merchant Land Limited | Professional & scientific | 1998 |
| Merchant PR Limited | Professional & scientific | 2005 |
| Merdon Court Management Company Limited | Real estate | 1995 |
| Merdon Financial Ltd | Financial services | 2011 |
| Mere Code Limited | Information & communication | 2025 |
| Mere Securities Limited | Real estate | 1979 |
| Meridian Safety Solutions Limited | Professional & scientific | 2007 |
| Mersenne IT Limited | Information & communication | 2007 |
| Meta Cloud Networks Ltd | Information & communication | 2024 |
| Metal Monkey Software Ltd | Information & communication | 2013 |
| Metcalfe Installations Ltd | Other services | 2014 |
| Meteoric Ltd | Information & communication | 2003 |
| Methasoft UK Limited | Extraterritorial | 2009 |
| MEU Construction Ltd | Construction | 2025 |
| Mewe Limited | Manufacturing | 2026 |
| MFD Communication Infrastructure Ltd | Professional & scientific | 2011 |
| MG Tax Services Limited | Professional & scientific | 2015 |
| MGA Garage Services Limited | Wholesale & retail | 2022 |
| Mgcl Limited | Professional & scientific | 2007 |
| MH & FH (GB) Property Investment Ltd | Financial services | 2023 |
| MH Bespoke Renovations Ltd | Construction | 2026 |