| Monarch Jewels Limited | Wholesale & retail | 1988 |
| Moncrisp Properties Limited | Construction | 1992 |
| Mondital Limited | Wholesale & retail | 2007 |
| Moneli Golara Limited | Health & social care | 2014 |
| Money Advice Liaison Group | Professional & scientific | 2015 |
| Monkeymoo Ltd | Manufacturing | 2023 |
| Monkhams Lane Property Ltd | Real estate | 2022 |
| Mons Montis Ltd | Information & communication | 2003 |
| Montade Limited | Real estate | 2021 |
| Montage Recruitment Consultancy Limited | Administrative & support | 2011 |
| Montagues Property Management Limited | Real estate | 2003 |
| Montalt Limited | Professional & scientific | 2012 |
| Montalt Management Limited | Households | 2004 |
| Moon Voice Solution Limited | Wholesale & retail | 2025 |
| Moonlight Furniture Limited | Wholesale & retail | 2026 |
| Moore Technologies Ltd | Information & communication | 2023 |
| Moorefield Estates Ltd | Real estate | 2019 |
| Moorepeople People Ltd | Administrative & support | 2021 |
| Moorglow Limited | Real estate | 1996 |
| Morelag Insulation Ltd | Construction | 2007 |
| Morgan PUB Holdings Ltd | Financial services | 2019 |
| Morgun Electrics Limited | Energy | 2020 |
| Mormont & Douglas Properties Limited | Real estate | 2022 |
| Morpheus Capital Limited | Financial services | 2021 |
| Morphosis Partners Limited | Administrative & support | 2014 |
| Morton Insurance Brokers Limited | Financial services | 1972 |
| MOS Training Center Ltd | Construction | 2020 |
| Mosaic Cafe Ltd | Hospitality | 2021 |
| Mosaic Property Management Ltd | Administrative & support | 2022 |
| Mossford Fire Protection Ltd | Construction | 2018 |
| Motherhood Health Care Ltd | Health & social care | 2011 |
| Motivated by Music Ltd | Arts & recreation | 2024 |
| Motive & CUE Limited | Professional & scientific | 2018 |
| Moto Collective Limited | Administrative & support | 2025 |
| Motta Investments Limited | Real estate | 2016 |
| Moulsham Lettings Limited | Hospitality | 2011 |
| Mount Pleasant Investments Limited | Real estate | 2011 |
| Mouse and Grape Ltd | Wholesale & retail | 2020 |
| Move Rouge Ltd | Transport & logistics | 2025 |
| Moxie Holdings Ltd | Financial services | 2024 |
| MP Property Trading Limited | Real estate | 2020 |
| MP Roofing Services Ltd | Construction | 2021 |
| MPV & SUV Solutions Ltd | Other services | 2019 |
| MR Clearance Ltd | Water & waste | 2022 |
| MR Janj Limited | Administrative & support | 2018 |
| MR Shelby's Barbers Ltd | Other services | 2022 |
| Mr,Anunimorigba Fleet Limited | Administrative & support | 2025 |
| Mreps Trustees (NO 33) Limited | Professional & scientific | 2003 |
| Mrhre Limited | Real estate | 2022 |
| MRY Renewables Limited | Professional & scientific | 2020 |
| MRZ PMC Ltd | Professional & scientific | 2025 |
| MS Consulting Partners Limited | Professional & scientific | 2022 |
| MS Prop Limited | Construction | 2021 |
| Mschb Ltd | Wholesale & retail | 2018 |
| Mskin & Aesthetics Limited | Other services | 2023 |
| Mspn Property Limited | Real estate | 2016 |
| Mswp Properties Ltd | Real estate | 2022 |
| MTB Trading Ltd | Professional & scientific | 2014 |
| Mtchmkr Ltd | Arts & recreation | 2022 |
| MTH Contracts Ltd | Construction | 2018 |
| MTH Grab Services Limited | Construction | 2022 |
| MTH Group Holdings Limited | Construction | 2015 |
| MTH Plant & Vehicle Hire Limited | Administrative & support | 2020 |
| MTH Traffic Management Limited | Professional & scientific | 2013 |
| MTK Drylining Ltd | Construction | 2018 |
| Mudec Group Ltd | Financial services | 2024 |
| Mughal Motors Limited | Wholesale & retail | 2021 |
| Muizz Ltd | Real estate | 2017 |
| Mukunda Ltd | Real estate | 2020 |
| Mularov Ltd | Construction | 2019 |
| Mularova 2019 Ltd | Transport & logistics | 2024 |
| Mulcleanear Ltd | Other services | 2026 |
| Mullish Consultancy Ltd | Health & social care | 2022 |
| Multiplus Tax Solutions Ltd | Professional & scientific | 2014 |
| Muminoiz Ltd | Health & social care | 2021 |
| Murphy Designs Limited | Real estate | 2003 |
| Murray & Sullivan Invest Limited | Real estate | 2019 |
| Mury Construction Limited | Manufacturing | 2018 |
| Museum Cafe E2 Ltd | Hospitality | 2015 |
| Museums & Expos International Limited | Administrative & support | 2005 |
| Music for Baby Limited | Wholesale & retail | 2010 |
| Mustard (Clothing) Limited | | 1985 |
| Mustard NOT Custard Ltd | Professional & scientific | 2018 |
| MVA Maintenance Ltd | Construction | 2018 |
| MVC Services Limited | Transport & logistics | 2015 |
| MWM Management Services Ltd | Professional & scientific | 2016 |
| My Best Friends Wardrobe Ltd | Wholesale & retail | 2019 |
| My Clinical Club Limited | Other services | 2025 |
| My Dream Kitchen Limited | Wholesale & retail | 2009 |
| My Extension Ltd | Construction | 2015 |
| My Little MOO Ltd | Hospitality | 2018 |
| My Property Ltd | Real estate | 2020 |
| My Trade Store Ltd | Wholesale & retail | 2026 |
| Myatt's Field Development LLP | | 2012 |
| Myatt's Field Management Company Limited | Real estate | 2011 |
| MYD Studio Limited | Construction | 2017 |
| Mydog Limited | Households | 2007 |
| Myers & Co.Accountants Limited | Professional & scientific | 2003 |
| Mykolly Limited | Information & communication | 2026 |
| Myrey Housing Limited | Real estate | 2021 |