| MHC Lettings Ltd | Real estate | 2008 |
| MI Engage Limited | Information & communication | 2025 |
| Michael D Morris Architects Limited | Professional & scientific | 2003 |
| Michael Sheinberg Ltd | Professional & scientific | 2014 |
| Michelle Hall Coaching & Consulting Limited | Professional & scientific | 2023 |
| Middle East Insider Ltd | Information & communication | 2014 |
| Midslot Property Management Limited | Real estate | 1988 |
| Mighty Convoy Ltd. | Health & social care | 2022 |
| Mignonne Company Limited | Hospitality | 2021 |
| Mijo Property Limited | Real estate | 2018 |
| Mike Drury Jibs Ltd | Information & communication | 2012 |
| Mikewebbpharma Ltd | Professional & scientific | 2018 |
| Mildan Ltd | Financial services | 2017 |
| Milestone Commercial Agency Ltd | Real estate | 2001 |
| Milka Properties Limited | Real estate | 2021 |
| Millerworld Ltd | Information & communication | 2010 |
| Million Services Limited | Professional & scientific | 2019 |
| MIMMO27 Limited | Hospitality | 2022 |
| Mindlab Services Limited | Education | 2016 |
| Minerva Financial Ltd | Professional & scientific | 2025 |
| Mingolabs Limited | Information & communication | 2016 |
| Mint Fish Limited | Financial services | 2014 |
| Miraculum Entertainment Limited | Arts & recreation | 2025 |
| Mirailab Bioscience UK Ltd | Manufacturing | 2022 |
| MIS Technology Limited | Professional & scientific | 2007 |
| Mission Publishing Limited | Information & communication | 2009 |
| Mission Recordings Limited | Information & communication | 2009 |
| MJF Business Development Consulting Limited | Professional & scientific | 2011 |
| MJM Carpentry & Building Services (UK) Limited | Construction | 2005 |
| MKM Research Labs UK Limited | Professional & scientific | 2025 |
| MLC London Limited | Health & social care | 2015 |
| MM Design and Engineering Services Ltd | Construction | 2022 |
| Mmhf Ltd | Manufacturing | 2021 |
| MN International Group Ltd | Financial services | 2025 |
| Mnvw Group Limited | Professional & scientific | 2018 |
| Mocka Sandwich Bar Limited | Hospitality | 2014 |
| Modern Ford Investments Limited | Construction | 2025 |
| Modern Ford Limited | Professional & scientific | 2017 |
| Mohill Limited | Construction | 2020 |
| Money Flow Ltd | Financial services | 2006 |
| Monitor Exploration Limited | Mining & quarrying | 2018 |
| Mono Cycling Ltd | Manufacturing | 2016 |
| Monolite Engineering Ltd | Professional & scientific | 2016 |
| Montana Management (UK) Limited | Real estate | 2011 |
| Montedellago Ltd | Professional & scientific | 2025 |
| Moonlight Mars Limited | Construction | 2016 |
| Moor Property Limited | Financial services | 2021 |
| More Tutoring Ltd | Education | 2015 |
| Morello Mortgages Limited | Financial services | 2008 |
| Moreno Masey Limited | Professional & scientific | 2007 |
| Morling Holdings Limited | Real estate | 2016 |
| Morton Media Communications Limited | Administrative & support | 2018 |
| Moskito Ventures Consulting Limited | Professional & scientific | 2018 |
| Mote Leisure Limited | Education | 1999 |
| Motel Trading Company Limited | Professional & scientific | 2020 |
| Motionspot Ltd | Other services | 2012 |
| Motorsportforex Limited | Financial services | 2016 |
| Mount Lodge Hanover Court Limited | Households | 2023 |
| Mountainhale Limited | Professional & scientific | 2025 |
| Mountainview Learning Limited | Professional & scientific | 2004 |
| MR Monkey SOX C.I.C. | Wholesale & retail | 2018 |
| MR PIG Stuff Ltd | Hospitality | 2014 |
| Mrowka Limited | Wholesale & retail | 2014 |
| MS Surveying Services Ltd. | Professional & scientific | 2015 |
| MSP 2024 Limited | Professional & scientific | 2024 |
| MTD17 Limited | Information & communication | 2023 |
| Mther Talent Ltd | Professional & scientific | 2024 |
| Mtsh Consultancy Ltd | Professional & scientific | 2009 |
| Mulberry Court RTM Company Limited | Households | 2021 |
| Multisoft Consulting UK Ltd | Information & communication | 2009 |
| Munro Carr Limited | Professional & scientific | 2014 |
| Munster Court (Teddington)Residents Association Limited | Households | 1962 |
| Murphy Partnership Limited | Professional & scientific | 2021 |
| Murray Court Residents Association Limited | Households | 1969 |
| Music Fountain Education Limited | Administrative & support | 2009 |
| Music Heritage London Limited | Administrative & support | 2014 |
| Music Teacher Ltd | Other services | 2020 |
| Musology Consulting London Limited | Information & communication | 2022 |
| Mutabalis Ltd | Information & communication | 2021 |
| MW Prime Consulting Limited | Professional & scientific | 2026 |
| Mwanza Air Limited | Transport & logistics | 2012 |
| My NET Accountant Limited | Professional & scientific | 2020 |
| My Physiotherapy Limited | Other services | 2015 |
| My Property Trainer Limited | Education | 2020 |
| My Vineyard Limited | Agriculture & fishing | 2014 |
| Myddeltons Limited | Wholesale & retail | 1997 |
| Mylor Properties Ltd | Real estate | 2016 |
| N & D Properties Limited | Real estate | 2007 |
| N4J Partnerships Ltd | Administrative & support | 2024 |
| Nacuhe Limited | Wholesale & retail | 2026 |
| NAH Estates Limited | Real estate | 2005 |
| Naked EYE Research Limited | Other services | 2003 |
| Nandnor Ltd | Professional & scientific | 2017 |
| Nanotek Energy Limited | Professional & scientific | 2018 |
| NAP Data Analytics Limited | Information & communication | 2014 |
| NAQ Productions Ltd | Information & communication | 2023 |
| Narrow Water Partners Ltd | Financial services | 2022 |
| Natbot Ltd | Information & communication | 2021 |
| Nathalie Anne-Carole | Extraterritorial | 2025 |
| Nathalie-Anne-Carole Tuel Limited | Extraterritorial | 2023 |