| Mikami Investment Limited | Real estate | 2023 |
| Mike MK Limited | Construction | 2025 |
| Mikemar Care Solutions Limited | Health & social care | 2014 |
| Miles Archer Limited | Financial services | 2001 |
| Milford Estates (Tonbridge) Limited | Real estate | 2000 |
| Millbank Lifts Limited | Manufacturing | 2008 |
| Miller Wheel & Cultivator Co.Limited(The) | Agriculture & fishing | 1940 |
| Miller Wheel Cultivator Holdings Limited | Extraterritorial | 2016 |
| Miller Wheel Holdings Limited | Financial services | 2015 |
| Miller Wheel Properties Limited | Real estate | 2015 |
| Miller Wheel Property Holdings Limited | Extraterritorial | 2016 |
| Millers GAS Services Ltd | Construction | 2023 |
| Millerst Limited | Health & social care | 2015 |
| Millhaven Investments Ltd | Real estate | 2024 |
| Millhill Properties (Horley) Limited | Real estate | 2014 |
| Millhill Properties (Leatherhead) Limited | Construction | 2011 |
| Millhill Properties [Lewes] Limited | Construction | 2013 |
| Million Wide Ltd | Wholesale & retail | 2019 |
| Millport Lettings Ltd | Real estate | 2025 |
| Millport London Limited | Construction | 2025 |
| Millport Properties Ltd | Real estate | 2025 |
| Millwood Road Allotments Ltd | Arts & recreation | 2020 |
| Milroy Developments Limited | Construction | 2016 |
| Milroy Holdings Limited | Professional & scientific | 1993 |
| Milroy Investments Limited | Real estate | 1995 |
| Milulo Creations Limited | Health & social care | 2023 |
| Mima Ventures Ltd | Health & social care | 2023 |
| Mimansa Limited | Administrative & support | 2016 |
| Min's Incorporated Ltd | Wholesale & retail | 2019 |
| Minakos Capital Advisors Ltd | Administrative & support | 2016 |
| Mindset Homes Ltd | Households | 2019 |
| Minerve Training Limited | Financial services | 2015 |
| Ming Investments Limited | Real estate | 1994 |
| Mini Moon Theatre Ltd | Arts & recreation | 2025 |
| Mintcrest Limited | Real estate | 2001 |
| Minty Productions Limited | Information & communication | 2011 |
| Miracle Kitchen 4 YOU Ltd | Extraterritorial | 2011 |
| Mircea Install Ltd | Construction | 2014 |
| Mirix Limited | Professional & scientific | 2015 |
| Mirza & Zaidi Limited | Real estate | 2015 |
| Misha Roofing Ltd | Construction | 2015 |
| Mishras Consulting Limited | Information & communication | 2024 |
| Mishras Investments Limited | Real estate | 2023 |
| Miso Limited | Hospitality | 1999 |
| Miss Catch’Em Pest Control Ltd | Water & waste | 2022 |
| Missy Mop-It Maintenance Ltd | Administrative & support | 2018 |
| Mister Nice OPS Limited | Hospitality | 2021 |
| Mistry Property Management Company Limited | Real estate | 2018 |
| Mitchell's Moving Company Ltd | Transport & logistics | 2025 |
| Mitev Ltd | Construction | 2013 |
| Mitolake Ltd | Wholesale & retail | 2024 |
| Miyu London Ltd | Other services | 2015 |
| MJ Armstrong Building Services Limited | Construction | 2018 |
| MJ CIA Ltd | Professional & scientific | 2026 |
| MJ Civil Engineering Solutions Limited | Construction | 2020 |
| MJ Phoenix Travel Agency Ltd | Real estate | 2023 |
| MJ Properties London Ltd | Construction | 2016 |
| MJ Property Constructions Ltd | Construction | 2019 |
| MJC Electric Ltd | Construction | 2007 |
| MJD Creative Ltd | Information & communication | 2016 |
| MJM Family Office Ltd | Financial services | 2025 |
| MJT Electrical & Maintenance Ltd | Construction | 2022 |
| MK Design Creations Limited | Professional & scientific | 2018 |
| MK DRY Cleaning Limited | Wholesale & retail | 2019 |
| MKF Estates Limited | Real estate | 2025 |
| MKH Holdings Ltd | Real estate | 2025 |
| Mkyt Ltd | Professional & scientific | 2017 |
| ML Spares Ltd | Manufacturing | 2022 |
| MLC Analytics Ltd | Professional & scientific | 2023 |
| MM Bexley Ltd | Administrative & support | 2008 |
| MM Shades Ltd | Professional & scientific | 2014 |
| MMA Investment Properties Limited | Real estate | 2024 |
| MMO Brothers Limited | Real estate | 2021 |
| MNJ Property Services Ltd | Real estate | 2025 |
| MO House Studio Ltd | Wholesale & retail | 2026 |
| Mobile Phone Corner Ltd | Wholesale & retail | 2025 |
| Mobilepower Charging Concept UK Ltd | Wholesale & retail | 2026 |
| Mocco Ltd | Manufacturing | 2026 |
| Modeco Interiors Limited | Extraterritorial | 2021 |
| Modelmole Ltd | Information & communication | 2023 |
| Moduform Construction Ltd | Construction | 2021 |
| Modus Creative Limited | Professional & scientific | 2018 |
| MOG.UK25 Ltd | Wholesale & retail | 2026 |
| Mojo Intellectual Property Limited | Professional & scientific | 2026 |
| MON573R Collectables Ltd | Wholesale & retail | 2026 |
| Mona Services Limited | Other services | 1987 |
| Monadic Systems Ltd | Information & communication | 2022 |
| Money Thoughts Ltd | Information & communication | 2020 |
| Montbretia Property Limited | Administrative & support | 2002 |
| Montessori Seedlings Limited | Education | 2023 |
| Moomoth Global Limited | Information & communication | 2021 |
| Moon A.C. Limited | Construction | 1997 |
| Moonshine Productions Ltd | Information & communication | 2012 |
| Moore Utilities Limited | Construction | 2017 |
| Mor-Tech Consultants Ltd | Administrative & support | 2023 |
| Mor-Tech Group Ltd | Financial services | 2024 |
| Moran Estimating & Surveying Services Limited | Professional & scientific | 2019 |
| Morden Lodge (Beckenham Grove) Management Limited | Households | 1969 |
| More Scaffolding Services Ltd | Construction | 2015 |
| Moresuccessfba Ltd | Wholesale & retail | 2024 |