| Maverick Apps Private Limited | Information & communication | 2025 |
| MAX TAC Ltd | Manufacturing | 2026 |
| Mayflower Stores Limited | Wholesale & retail | 2008 |
| Mayne Electrical Supplies Limited | Wholesale & retail | 2010 |
| Maysi Limited | Information & communication | 2014 |
| Maysi Property Limited | Real estate | 2017 |
| MAZ Consultancy Limited | Professional & scientific | 2026 |
| Mazz Interiors Ltd | Real estate | 2024 |
| MB Design & Fit Limited | Construction | 2016 |
| MBC Plus Limited | Wholesale & retail | 2025 |
| MC Visage Ltd | Other services | 2016 |
| Mcdaid Building Services Limited | Construction | 2016 |
| Mcgrath Development & Construction Ltd | Construction | 2006 |
| Mcgrath Homes Ltd | Hospitality | 2001 |
| Mcgrath Rentals Ltd | Real estate | 2021 |
| Mcmahon Investments Limited | Financial services | 2025 |
| Mcnamee Ltd | Real estate | 2014 |
| MCS Business Ltd | Transport & logistics | 2024 |
| MCS Creative Limited | Professional & scientific | 1983 |
| Md-M Electrical Contractors Ltd | Construction | 2026 |
| Mdmc Developments Limited | Construction | 2020 |
| Mead Civil Engineering & Groundworks Limited | Construction | 2019 |
| Meadow Hill Financial Services Ltd | Professional & scientific | 2018 |
| Meadows Forensics Limited | Administrative & support | 2004 |
| Meat Lift UK Ltd | Information & communication | 2017 |
| Mechanical & Plumbing Services London Limited | Construction | 2023 |
| Mechanical Paul Ltd | Wholesale & retail | 2020 |
| Medbridge Consulting Limited | Administrative & support | 2025 |
| Medialis Wellbeing CIC | Education | 2022 |
| Medjay Security Solutions Limited | Administrative & support | 2023 |
| Medow Care Services Limited | Health & social care | 2011 |
| Medpharmpro Ltd | Health & social care | 2025 |
| Meghana's Collections Ltd | Manufacturing | 2021 |
| Meglog Ltd | Health & social care | 2026 |
| Mehti Transport Ltd | Transport & logistics | 2023 |
| Mekcek Shop Ltd | Wholesale & retail | 2025 |
| Melemm Ltd | Construction | 2023 |
| Meli Wines Ltd | Information & communication | 2026 |
| Melkar Limited | Wholesale & retail | 2025 |
| Mendogas Ltd | Construction | 2014 |
| Mercato Principale Ltd | Wholesale & retail | 2023 |
| Merchant Business Systems Limited | Extraterritorial | 1983 |
| Merchant Systems Limited | Extraterritorial | 1979 |
| Mercury Global Systems Limited | Extraterritorial | 2020 |
| Merridene Residents Company Limited | Real estate | 1981 |
| Metabolic Insights Limited | Health & social care | 2019 |
| Metalayer Investments Limited | Real estate | 2025 |
| Mete Logistics Ltd | Transport & logistics | 2018 |
| Methi Flavour Ltd | Hospitality | 2019 |
| Meticulous Cleaning Solution Ltd | Administrative & support | 2024 |
| Metropolis Consultants Limited | Professional & scientific | 2026 |
| Metropolis Lettings Ltd | Real estate | 2024 |
| MFA Studios Limited | Arts & recreation | 2017 |
| MFI3 Limited | Transport & logistics | 2016 |
| MGE Care Limited | Health & social care | 2022 |
| MGM BC LLP | | 2018 |
| MGM Herts Ltd | Construction | 2025 |
| MGN Construction Services Limited | Construction | 2012 |
| MHE Jvco Limited | Professional & scientific | 2013 |
| Mhrs Consulting Ltd | Information & communication | 2019 |
| Miah Brother Investments Limited | Real estate | 2018 |
| Miah Capital Limited | Real estate | 2018 |
| Mibel Ltd | Professional & scientific | 2020 |
| Micadiole Global Limited | Transport & logistics | 2018 |
| Mice Organiser Ltd | Administrative & support | 1994 |
| Michael Laurie Magar Limited | Real estate | 2000 |
| Michael Van Clarke LLP | | 2006 |
| Michael West Limited | Professional & scientific | 1999 |
| Michleham Property Investments Limited | Real estate | 2002 |
| Mictrans Ltd | Transport & logistics | 2018 |
| Miella Construction Ltd | Construction | 2026 |
| Miflun Limited | Information & communication | 2018 |
| Mighty Recruitment Ltd | Construction | 2020 |
| Miketattoo Ltd | Arts & recreation | 2023 |
| Milano Menswear Limited | Wholesale & retail | 2025 |
| Millennium Ladieswear Manufacturers Limited | Manufacturing | 1998 |
| Miller Investment Group Limited | Real estate | 2024 |
| Milvus-I Consulting Limited | Professional & scientific | 2022 |
| Mima Atelier Ltd | Wholesale & retail | 2026 |
| Mimram Valley Butchers Ltd | Wholesale & retail | 2024 |
| Mimram Valley Holdings Ltd | Financial services | 2024 |
| Minnulah Limited | Wholesale & retail | 2024 |
| Mint Solutions UK Limited | Information & communication | 1997 |
| Mint Wood Flooring Ltd | Construction | 2020 |
| Miracle Leak Detection Limited | Other services | 2019 |
| Miracle Moments (UK) | Other services | 2010 |
| Miskp Ltd | Health & social care | 2025 |
| Miss Fixit Plumbing & Heating Limited | Construction | 2025 |
| Mistry & Associates Building Services Limited | Construction | 2013 |
| Mitton Ridge Partners Ltd | Professional & scientific | 2025 |
| Mizzy Limited | Health & social care | 2016 |
| MJ Construct Services Ltd | Construction | 2016 |
| MJ Project Engineering Limited | Professional & scientific | 2024 |
| MJO Solutions Limited | Professional & scientific | 2012 |
| Mjsstagework Limited | Construction | 2024 |
| MK Holdings Corporation Ltd | Financial services | 2024 |
| MK Pro Trading Ltd | Wholesale & retail | 2022 |
| MK45 Developments Limited | Construction | 2025 |
| Mkamba Ltd | Financial services | 2017 |
| MKF (2011) Limited | Arts & recreation | 2011 |