| Menwax Limited | Wholesale & retail | 2020 |
| Merdeka Ltd | Manufacturing | 2011 |
| Merlarri Limited | Health & social care | 2025 |
| Merritt QS Ltd | Professional & scientific | 2022 |
| Merry Mutts Dog Training Limited | Other services | 2010 |
| Metafort Security Limited | Administrative & support | 2023 |
| Metanoia Records Ltd | Information & communication | 2020 |
| Mezzaluna Group Limited | Hospitality | 2022 |
| MF Home Improvements Limited | Construction | 2023 |
| MG Building Services (Hampshire) Limited | Construction | 2021 |
| MGB 2005 Holdings Ltd | Financial services | 2010 |
| MH Medical Supplier Ltd | Manufacturing | 2025 |
| MHR Consultancy Limited | Professional & scientific | 2009 |
| MI Coffee & Cake Ltd | Hospitality | 2022 |
| MI Farnborough Ltd | Other services | 2026 |
| MI Home Heating Ltd | Construction | 2021 |
| MIB Business Consulting Ltd | Professional & scientific | 2019 |
| Michael a Jansen Limited | Administrative & support | 2025 |
| Michael Baker Solicitors Limited | Professional & scientific | 2003 |
| Michael Dillon Coaching Limited | Administrative & support | 2022 |
| Michael Simpson Limited | Professional & scientific | 2010 |
| Michal Cienki Limited | Transport & logistics | 2015 |
| Micromoment Marketing Limited | Professional & scientific | 2026 |
| Micron Properties Limited | Real estate | 2011 |
| Midas Developments Ltd | Construction | 2013 |
| Midnight Lace Ltd | Wholesale & retail | 2023 |
| Mike Kearsey Limited | Arts & recreation | 2011 |
| Mike Pierce Properties Ltd | Construction | 2013 |
| Milestogo Limited | Real estate | 2020 |
| Miller Charles Developments Limited | Construction | 2014 |
| Millstone (Rowledge) Limited | Construction | 2016 |
| Millstone Homes Denham Limited | Construction | 2024 |
| Millstone Homes Limited | Construction | 2011 |
| Millstone Homes Tring Limited | Construction | 2019 |
| Millwright Services Ltd | Manufacturing | 2015 |
| Milog Consulting Ltd | Information & communication | 2023 |
| Mimosa Court Residents Company Limited | Real estate | 2006 |
| Mind Care Professionals Limited | Health & social care | 2025 |
| Mind of Design Limited | Information & communication | 2012 |
| Mindglow Ltd | Education | 2023 |
| Ming FAN Catering Ltd | Hospitality | 2016 |
| Ming Property Ltd | Real estate | 2025 |
| Miniped Communications Ltd | Information & communication | 2020 |
| Minor Plus EST Limited | Real estate | 2022 |
| Minsep Limited | Mining & quarrying | 2010 |
| Minster International Business Development Limited | Professional & scientific | 1998 |
| Mirill Advisory Ltd | Arts & recreation | 2020 |
| Miron DAN Constantin Ltd | Extraterritorial | 2022 |
| Missionary Sisters’ Home Nursery Ltd | Education | 2023 |
| Mithun Enterprises Ltd | Hospitality | 2018 |
| MJ Brooks Consultancy Limited | Professional & scientific | 2023 |
| MJ Training Solutions UK Ltd | Education | 2018 |
| MJB Landscapes & Driveways Ltd | Administrative & support | 2020 |
| MJE Trading Limited | Wholesale & retail | 2021 |
| Mk&M Limited | Professional & scientific | 2017 |
| MML Technologies Ltd | Manufacturing | 2013 |
| MMS Trans Limited | Transport & logistics | 2026 |
| MNS Home and Properties Limited | Real estate | 2023 |
| Moerich.Sn Ltd | Financial services | 2016 |
| Mohawk Digital Marketing Ltd | Information & communication | 2025 |
| Mojo Visuals Ltd | Professional & scientific | 2020 |
| Mokb Limited | Hospitality | 2022 |
| Molco Trading Ltd | Wholesale & retail | 2012 |
| Molesey Sports Coaching Limited | Arts & recreation | 2024 |
| Molex Electronics Limited | Manufacturing | 1979 |
| Moliveros Limited | Manufacturing | 2022 |
| Molly Mural Ltd | Arts & recreation | 2024 |
| Momentum Group Limited | Professional & scientific | 2000 |
| Mondas Consulting Ltd | Administrative & support | 2007 |
| Mondo Italia Restaurant Ltd | Hospitality | 2024 |
| Mondocrm UK Ltd | Information & communication | 2023 |
| Money Leaf Finance Limited | Administrative & support | 2021 |
| Montecapri Limited | Manufacturing | 2024 |
| Moody Tech Ltd | Information & communication | 2021 |
| Moonwalk Homes Ltd | Construction | 2023 |
| Moorhouse Surveyors Limited | Professional & scientific | 2015 |
| Morgan Anderson & Whitter Ltd | Professional & scientific | 2003 |
| Mori & Co. Ltd | Professional & scientific | 2026 |
| Morningside Financial Services Limited | Financial services | 2022 |
| Motoright Limited | Wholesale & retail | 1997 |
| Motorola Mobility Holdings UK Limited | Financial services | 2017 |
| Motorola Mobility UK Ltd | Manufacturing | 2009 |
| MOVEMENT17 Academy Ltd | Arts & recreation | 2022 |
| Mowercare Limited | Manufacturing | 2007 |
| Moytura Care Consulting Ltd | Financial services | 2021 |
| MPM OIL (UK) Ltd | Manufacturing | 2011 |
| MPS Marketing Consultancy Ltd | Professional & scientific | 2023 |
| MR Gurkha Ltd | Hospitality | 2026 |
| MRJ Design & Build Ltd | Construction | 2014 |
| MRS Bizzy Wizzy Limited | Real estate | 2022 |
| MS4 Architects LLP | | 2022 |
| MS5 Limited | Professional & scientific | 2018 |
| MSB Alloy Wheel Refurbishment Limited | Wholesale & retail | 2011 |
| MSD Pensions Trustee Limited | Professional & scientific | 1990 |
| Msdi Photography Limited | Professional & scientific | 2017 |
| Msexperts Ltd | Information & communication | 2018 |
| MSG Motorcycles Limited | Wholesale & retail | 2007 |
| MSM Nutrition Consultancy Ltd | Health & social care | 2019 |
| MSN Solutions Limited | Professional & scientific | 2016 |
| MSV Restaurants Ltd | Hospitality | 2022 |