| Meton Gravure Technologies UK Limited | Administrative & support | 2014 |
| Metropolitan Lettings Ltd | Real estate | 2024 |
| Mettavag MI Services Limited | Information & communication | 2016 |
| Mexica Chinese Buffet Ltd | Hospitality | 2024 |
| MG Accountancy Limited | Professional & scientific | 2025 |
| MG Barbers Ltd | Real estate | 2018 |
| Mgcouk Limited | Administrative & support | 2022 |
| Mgya Media Limited | Information & communication | 2006 |
| MH VET Supplies UK Ltd | Wholesale & retail | 2026 |
| MHE Brokers Limited | Administrative & support | 1972 |
| MHG Smith Limited | Construction | 2022 |
| MIA Kora Limited | Wholesale & retail | 2013 |
| Miasylvia Ltd | Manufacturing | 2023 |
| Michael Callan Limited | Information & communication | 2002 |
| Michail Protogerakis Limited | Health & social care | 2024 |
| Michelle Pauline Smith Limited | Financial services | 2022 |
| Michelle Wealth & Co Ltd | Real estate | 2019 |
| Michelle Wicke Childminding Limited | Health & social care | 2021 |
| Micklefield Hall Limited | Hospitality | 2017 |
| Microcad Software Services Limited | Administrative & support | 2014 |
| Mid-Career Transition Coach Ltd | Administrative & support | 2026 |
| Midas Retouching Ltd | Professional & scientific | 2008 |
| Midas UK Properties Ltd | Real estate | 2021 |
| Midnight Media Group Ltd | Professional & scientific | 2020 |
| Migaja Ltd | Information & communication | 2014 |
| Mighty Oak Mentoring CIC | Education | 2025 |
| Miles PER Hour Limited | Professional & scientific | 2008 |
| Mill END Bowls Club Limited | Arts & recreation | 2026 |
| Mill's & Trix Ltd | Other services | 2024 |
| Millennium Executive Limited | Transport & logistics | 2016 |
| Mimami Ltd | Wholesale & retail | 2017 |
| Minaur Corporate Finance Limited | Financial services | 2003 |
| Mincorp Limited | Mining & quarrying | 2025 |
| Mindset by Maya Ltd | Administrative & support | 2022 |
| Mini Bytes Services Limited | Education | 2022 |
| Mini Siam Ltd | Wholesale & retail | 2018 |
| Mini Siam Oriental Foods Ltd | Extraterritorial | 2020 |
| Minmax Limited | Manufacturing | 2000 |
| Minori London Limited | Hospitality | 2009 |
| Miracle Nails Limited | Other services | 2019 |
| Miraflores Investments Ltd | Real estate | 2020 |
| Miranee Limited | Health & social care | 2025 |
| Mirindal Consulting Limited | Professional & scientific | 2011 |
| Misbourne Investments Limited | Financial services | 2016 |
| Miss Smith Ltd | Wholesale & retail | 2013 |
| Mistry Consultancy Limited | Professional & scientific | 2018 |
| Mitisk Technologies Limited | Information & communication | 2004 |
| MJM Financial Solutions Limited | Information & communication | 2014 |
| MKA Consulting Limited | Information & communication | 2010 |
| Mkdz Ltd | Hospitality | 2024 |
| MKV Landsbergerstrasse Limited | Real estate | 2014 |
| MLC Courses Ltd | Education | 2022 |
| MLC Global Ltd | Education | 2019 |
| Mltutors Ltd | Information & communication | 2022 |
| MM Pharma Consultancy Ltd | Professional & scientific | 2024 |
| MM UK Property Developers Limited | Real estate | 2025 |
| MNA Investments Limited | Real estate | 2018 |
| MND Health Limited | Health & social care | 2009 |
| MNR Consultancy Limited | Professional & scientific | 2021 |
| MNS Tanning and Beauty Ltd | Other services | 2019 |
| Mobile Pavilion Events Ltd | Other services | 2020 |
| Mobilelink Accessories Ltd | Wholesale & retail | 2019 |
| Mobileneeds Ltd | Wholesale & retail | 2022 |
| Mobilize Lease & Co UK Limited | Financial services | 2023 |
| Modern Smile Ltd | Health & social care | 2026 |
| Modha Limited | Real estate | 2005 |
| Modo DI Marmi Limited | Construction | 2014 |
| Mohold Ltd | Financial services | 2022 |
| Moley Electrical Limited | Construction | 2014 |
| Monada Group Limited | Other services | 2017 |
| Monarch Care Limited | Health & social care | 2008 |
| Monarch KM Ltd | Health & social care | 2011 |
| Monarch Transformation Services Ltd | Information & communication | 2013 |
| Mondiale Ltd | Real estate | 2020 |
| Money Hill Development Ltd | Construction | 2021 |
| Moneyhill Equity Limited | Financial services | 2025 |
| Moniter (UK) Limited | Construction | 2000 |
| Monkeyton Properties Limited | Construction | 2021 |
| Montaze Broz Ltd | Construction | 2019 |
| Montway Construction Limited | Professional & scientific | 2005 |
| Montway Contracts Limited | Professional & scientific | 2005 |
| Montway Developments Limited | Professional & scientific | 2005 |
| Montway Homes Limited | Professional & scientific | 2005 |
| Montway Investments Limited | Professional & scientific | 2005 |
| Montway Limited | Construction | 1996 |
| Montway Projects Ltd | Construction | 2011 |
| Montway Properties Limited | Professional & scientific | 2005 |
| Montway Property Developments Limited | Construction | 2000 |
| Montway Structures Limited | Professional & scientific | 2005 |
| Moonlight 18 Ltd | Other services | 2024 |
| Moor Park Golf (Properties) Ltd | Arts & recreation | 2023 |
| Mooringtown Services Ltd | Professional & scientific | 2015 |
| Moorlake Ltd | Wholesale & retail | 2017 |
| Moorside Place Management Company Limited | Real estate | 2005 |
| Moose Rock Limited | Financial services | 2018 |
| Mores Consulting Ltd | Professional & scientific | 2016 |
| Morning Mugs Ltd | Hospitality | 2024 |
| Morphilibrium Ltd | Information & communication | 2007 |
| Morrow Civils Limited | Construction | 2025 |
| Morse Communications Limited | Financial services | 2003 |