| Made Your Day Limited | Wholesale & retail | 2019 |
| Made-To-Wear Limited | Extraterritorial | 2008 |
| Madebyade Ltd | Information & communication | 2019 |
| Magdalen House Limited | Health & social care | 2010 |
| Magic Dads Ltd | Extraterritorial | 2020 |
| Magnifi Global Ltd | Professional & scientific | 2021 |
| Mahsro Limited | Construction | 2017 |
| Maison Partners Ltd | Real estate | 2020 |
| Major 7TH Marketing Limited | Professional & scientific | 2026 |
| Major Look Limited | Professional & scientific | 2013 |
| Mallory Group Limited | Professional & scientific | 2016 |
| Maltsquare Limited | Households | 1984 |
| Mana Advisory Services Ltd | Information & communication | 2025 |
| Manheath Limited | Construction | 2017 |
| Manhood Limited | Construction | 1955 |
| Mani Sian Ltd | Professional & scientific | 2020 |
| Manor Court Farncombe Residents Association Limited | Households | 1983 |
| Manor Development Investments Ltd | Financial services | 2020 |
| Manor Wood Sports West Horsley Ltd | Extraterritorial | 2022 |
| Mansion (Newstead) Management Company Limited(The) | Households | 1975 |
| Manymickle Ltd | Professional & scientific | 2019 |
| Maoin Limited | Administrative & support | 2012 |
| March Hare Stud Ltd | Agriculture & fishing | 2023 |
| Mark David Dennis Limited | Professional & scientific | 2016 |
| Mark END Limited | Financial services | 2019 |
| Marshall & SON Electrics Limited | Energy | 2016 |
| Marshalls Solicitors LLP | | 2021 |
| Martens Place Limited | Households | 1996 |
| Martin Burford Limited | Professional & scientific | 2009 |
| Masella Coupe Estate Agents Limited | Real estate | 2008 |
| Masella Coupe Lettings Limited | Real estate | 2008 |
| Masella Coupe Ltd | Real estate | 2011 |
| Massive Marketing Ltd | Professional & scientific | 2024 |
| Material Procurement Solutions Limited | Administrative & support | 2016 |
| Mathieson Hawes Consulting Ltd | Information & communication | 2018 |
| Mathspace Emea PTY Ltd | Education | 2018 |
| Matprint Ltd | Wholesale & retail | 2012 |
| Matrix MAN and Van Ltd | Transport & logistics | 2017 |
| Matrix Property Clearance Ltd | Transport & logistics | 2019 |
| Matt Gregory Management Ltd | Arts & recreation | 2019 |
| Matt Macland Ltd | Professional & scientific | 2017 |
| Matt Smithers Marketing Consultancy Limited | Professional & scientific | 2021 |
| Matthew Holland Ltd | Manufacturing | 2022 |
| Mattwell Developments Limited | Construction | 2010 |
| Mattwell Homes Limited | Professional & scientific | 2011 |
| Mattwell Investments Ltd | Real estate | 2017 |
| Mattwell Investments Residential Ltd | Real estate | 2021 |
| MAX Interiors Ltd | Administrative & support | 2016 |
| MAX Phillips Limited | Professional & scientific | 2025 |
| MAX Routledge Ltd. | Agriculture & fishing | 2016 |
| MAX Routledge Services Ltd | Agriculture & fishing | 2016 |
| Maxfield Music Tuition Limited | Education | 2002 |
| Mayfield House SPV Ltd | Real estate | 2021 |
| Mayphil Park Sales Limited | Real estate | 2015 |
| MBL Accountancy Solutions Limited | Professional & scientific | 2022 |
| MBL Business Services Limited | Professional & scientific | 2010 |
| Mcanicus Ltd | Wholesale & retail | 2017 |
| Mccoy's Limited | Hospitality | 1986 |
| Mckenzie Fine Wines Limited | Wholesale & retail | 2007 |
| Mclaren Capital Limited | Administrative & support | 2008 |
| MCM Group Ltd | Wholesale & retail | 2025 |
| MEA Hother Limited | Professional & scientific | 2021 |
| Mead Court Residents Limited | Other services | 1970 |
| Mearns & Pike Ltd | Professional & scientific | 2017 |
| Media Monitors UK Limited | Information & communication | 2001 |
| Mediaframe Ltd | Information & communication | 2007 |
| Medical Investment & Advisory Services LLP | | 2012 |
| Medikuo Healthcare Limited | Health & social care | 2016 |
| Medirek Ltd | Health & social care | 2022 |
| MEL Entertainment Ltd. | Education | 1994 |
| MEL7 & Co LLP | | 2017 |
| Melanie Martin Health Limited | Health & social care | 2026 |
| Mellyzx Ltd | Wholesale & retail | 2026 |
| Melmoth Hall Limited | Professional & scientific | 2010 |
| Meridian Commercial Property Partners Ltd | Real estate | 2026 |
| Merrari Limited | Wholesale & retail | 2011 |
| Merry Harriers PUB Co Ltd | Hospitality | 2023 |
| Merwil Consulting Ltd | Mining & quarrying | 2022 |
| Metal Events Limited | Information & communication | 2001 |
| Metamex Engineering Limited | Professional & scientific | 2019 |
| Metrion Ltd | Other services | 2023 |
| Mexicocall Limited | Real estate | 1999 |
| MFM Associates Ltd | Professional & scientific | 2023 |
| MGE Building Solutions Limited | Construction | 2006 |
| MGE Coppicing Limited | Agriculture & fishing | 2011 |
| MGT Building Services Ltd | Construction | 2020 |
| Mhuk Limited | Wholesale & retail | 2023 |
| Michael Guest Associates Ltd | Professional & scientific | 2007 |
| Michael J Gallagher Contractors Limited | Construction | 1965 |
| Michael J WEY & Co Limited | Professional & scientific | 2003 |
| Michelle Renee Limited | Other services | 2005 |
| Mick Jolly Car Body Repairs Limited | Extraterritorial | 2017 |
| Migrate Media Limited | Information & communication | 2010 |
| Miguel and Maria Povoas Ltd | Health & social care | 2014 |
| Mikemack Ltd | Wholesale & retail | 2022 |
| Milanaut Limited | Professional & scientific | 2015 |
| Milford and Villages Day Centre | Extraterritorial | 1996 |
| Milk NO Sugar Clothing Ltd | Wholesale & retail | 2022 |
| Milkwood Studio Ltd | Arts & recreation | 2024 |
| Mill Lane Imaging Ltd | Health & social care | 2023 |