| Male Design Limited | Other services | 2005 |
| Malindi Holdings Limited | Construction | 2022 |
| Malins Affordable Homes Limited | Real estate | 2013 |
| Malins Property Management Limited | Households | 2023 |
| Malkeet Mangat Roofing & Building Contractors Ltd | Construction | 2011 |
| Management Horizons Ltd | Extraterritorial | 2010 |
| Management Shift Solutions Limited | Professional & scientific | 2015 |
| Manby Holdings Limited | Financial services | 2024 |
| Mancini Celebrity Events Limited | Administrative & support | 2018 |
| Mangoeq Ltd | Information & communication | 2019 |
| Manielli Property Limited | Real estate | 2014 |
| Manielli Ventures Limited | Professional & scientific | 2006 |
| Manley Gough (UK) Ltd | Real estate | 2017 |
| Manpreet Gill Limited | Real estate | 2016 |
| Mantra Operations Services Ltd | Professional & scientific | 2017 |
| Mantra Operations Solutions Ltd | Professional & scientific | 2015 |
| Many IT Market Solutions Online Ltd | Information & communication | 2022 |
| Maplin Properties Limited | Real estate | 1991 |
| Maquay Investments Ltd | Hospitality | 2014 |
| March Homes Limited | Construction | 2004 |
| Marcus-Munro Limited | Construction | 2016 |
| Margary Wade Limited | Professional & scientific | 2017 |
| Marinell Limited | Administrative & support | 2023 |
| Mark Hill Publishing Limited | Information & communication | 2009 |
| Mark Rogers Consulting Limited | Information & communication | 2023 |
| Mark Woolhouse Limited | Professional & scientific | 2020 |
| Marketing Impact Limited | Professional & scientific | 1990 |
| Marketingwithmike Limited | Professional & scientific | 2020 |
| Marlborough Asset Management Limited | Real estate | 2020 |
| Marlborough Precision Limited | Professional & scientific | 1966 |
| Marlow Wishing Well LLP | | 2008 |
| Marlows Holdings Ltd | Real estate | 2025 |
| Marmimi Holding Limited | Financial services | 2025 |
| Marrell Consultancy Limited | Administrative & support | 2011 |
| Marsen Consultancy Limited | Professional & scientific | 2024 |
| Martin & Wheatley Investments Limited | Other services | 2022 |
| Martin & Wheatley Limited | Real estate | 2014 |
| Martin and Wheatley Sales Limited | Real estate | 2020 |
| Martin Duggan Ventures Limited | Information & communication | 2016 |
| Martin Prescott Investments Limited | Construction | 1962 |
| Marwell Roofing Company Limited | Construction | 1996 |
| Massanz Commodities Ltd | Wholesale & retail | 2020 |
| Masterbet Limited | Financial services | 2011 |
| Material Network Limited | Construction | 2022 |
| Matt Hoad Limited | Professional & scientific | 2009 |
| Matt Richards Consulting Ltd | Professional & scientific | 2017 |
| Matthew Halsall Consultancy Limited | Professional & scientific | 2013 |
| Maverick Hold Co Ltd | Professional & scientific | 2022 |
| Mawhood PUB Co Ltd | Hospitality | 2024 |
| Max-Gear Innovations Limited | Information & communication | 2010 |
| Maxest International Limited | Administrative & support | 2023 |
| Maxian Homes Limited | Construction | 2008 |
| Maxval Consultancy Limited | Professional & scientific | 2022 |
| Maxwell Financial Limited | Financial services | 2021 |
| MAY Elegance Ltd | Other services | 2025 |
| Maybury Hill Developments Limited | Construction | 2015 |
| Mayfair (Broadlands) Residents Management Company Limited | Households | 2018 |
| Mayfair Design Partners Ltd. | Construction | 2019 |
| Mayfair Glass Ltd | Construction | 2024 |
| Mayrose Investments Limited | Professional & scientific | 2010 |
| Mayrose Propco Limited | Extraterritorial | 2011 |
| MB Legal Services Limited | Professional & scientific | 2011 |
| MC Perran Properties Limited | Real estate | 2022 |
| MCF Tech Limited | Wholesale & retail | 2024 |
| MCF Technology Limited | Information & communication | 2019 |
| MCL Projects (QS) Limited | Administrative & support | 2014 |
| Mclaren Hospitality Ltd | Wholesale & retail | 2019 |
| Mcnamara Haulage Limited | Transport & logistics | 2002 |
| MCV Financial Services Limited | Professional & scientific | 2016 |
| Mddp Limited | Professional & scientific | 2011 |
| MEA Vitae Limited | Extraterritorial | 2018 |
| Meadows Ryan Solicitors Ltd | Professional & scientific | 2014 |
| Medfair Ltd | Information & communication | 2016 |
| Media INK PR Limited | Professional & scientific | 2009 |
| Medialook Creative Productions Limited | Information & communication | 2015 |
| Mediamax Limited | Construction | 2012 |
| Medical Expert Witness Ltd | Health & social care | 2011 |
| Medical Health Limited | Health & social care | 2020 |
| Medilaw Solutions Ltd | Public administration | 2023 |
| Medlen Property Ltd | Real estate | 2020 |
| Medway Packaging Pension Trustee Limited | Professional & scientific | 1987 |
| Meetings on Autopilot Limited | Professional & scientific | 2024 |
| Megali-Property Ltd | Real estate | 2017 |
| Megalogics Limited | Information & communication | 2010 |
| Megin UK Ltd | Professional & scientific | 2019 |
| Melanie Charman Designs Ltd | Professional & scientific | 2016 |
| Melbury Close Ltd | Real estate | 2026 |
| Melcom Electronics Limited | Wholesale & retail | 1995 |
| Melissa Proles Consulting Limited | Professional & scientific | 2006 |
| Memorial Films Limited | Information & communication | 1966 |
| Mepstar Finance Limited | Administrative & support | 1977 |
| Merc Tech Autos Limited | Wholesale & retail | 2010 |
| Mercado Store Limited | Wholesale & retail | 2023 |
| Mercury Coaching Limited | Administrative & support | 2025 |
| Merlin Services Holdings Ltd | Professional & scientific | 2019 |
| Merlionbuild Limited | Construction | 2024 |
| Merton House (WJG) Limited | Health & social care | 2025 |
| Mesa Steward Inc Limited | Financial services | 2025 |
| Mescot Consulting Limited | Professional & scientific | 2021 |
| Mesh Media Ltd | Information & communication | 2025 |