| Modir Limited | Wholesale & retail | 2025 |
| Mohray Enterprise Ltd | Wholesale & retail | 2026 |
| Mojass Investments Limited | Real estate | 2023 |
| Moledina Limited | Wholesale & retail | 1995 |
| Moliztoks Health and Educational Services Ltd | Public administration | 2021 |
| Molusi College Old Students Association United Kingdom Chapter (Mocosa UK) | Education | 2020 |
| Monaes Tanning and Beauty Limited | Other services | 2024 |
| Monaflair Limited | Construction | 2001 |
| Monamore Ltd | Professional & scientific | 2017 |
| Moneta Document Storage Ltd | Administrative & support | 2005 |
| Moneta Probate Ltd | Professional & scientific | 2007 |
| Monii Properties Ltd | Real estate | 2023 |
| Monisha Raaj Limited | Other services | 2017 |
| Montessori Groups Ltd | Health & social care | 2025 |
| Monti Auto Ltd | Wholesale & retail | 2025 |
| Monty Media Ltd | Professional & scientific | 2021 |
| Monty's Leisure Limited | Hospitality | 2017 |
| Monty’S Functions Ltd | Hospitality | 2023 |
| Monyk Tania Limited | Wholesale & retail | 2018 |
| Monza Construction Limited | Construction | 2007 |
| Monza Group Holdings Limited | Financial services | 2024 |
| Monza Invest Limited | Real estate | 2025 |
| Moose & Goose Group Limited | Financial services | 2025 |
| Moose & Goose Properties Limited | Real estate | 2026 |
| Mooviereel Limited | Administrative & support | 2015 |
| Moozic Limited | Health & social care | 2021 |
| Morgan Thomas Construction Limited | Construction | 2007 |
| Morson Maintenance Group Limited | Construction | 2018 |
| Mortgage Star Limited | Administrative & support | 2022 |
| MOS Property Limited | Real estate | 2018 |
| Mosaic Life Support Limited | Health & social care | 2024 |
| Moses's Property Company Limited | Real estate | 2025 |
| Moss & Coleman Equity Release Limited | Administrative & support | 2023 |
| Moss & Coleman Solicitors Limited | Professional & scientific | 2019 |
| Moszur Ltd | Construction | 2015 |
| Motorcure Limited | Wholesale & retail | 2018 |
| Motoreksport Ltd | Wholesale & retail | 2021 |
| Mouthy Ltd | Health & social care | 2010 |
| Movexpress Limited | Transport & logistics | 2023 |
| Moviehaul Limited | Information & communication | 2014 |
| Mowataschi Limited | Wholesale & retail | 2025 |
| Moys Construction Ltd | Construction | 2025 |
| MP Valuations Limited | Financial services | 2025 |
| Mpanadas Limited | Manufacturing | 2025 |
| MPGM85 Limited | Health & social care | 2014 |
| MPL Digital Limited | Information & communication | 2024 |
| MQZ Investments Ltd | Real estate | 2024 |
| MR Brand Genie Ltd | Wholesale & retail | 2022 |
| MR FAT BAG Limited | Manufacturing | 2026 |
| MR Gadgets Ltd | Other services | 2026 |
| MR Global Solutions Ltd | Education | 2025 |
| MR P Kothari Ltd | Health & social care | 2026 |
| MR. Bunns & MR. Bagel Limited | Wholesale & retail | 2018 |
| Mr.B Rigging & Scaffolding Ltd | Construction | 2022 |
| MRC Worldwide Ltd | Transport & logistics | 2023 |
| MRK2 Alarms Ltd | Administrative & support | 2015 |
| MRS Maths Materials Ltd | Education | 2025 |
| MS Development Corporation Limited | Education | 2002 |
| MS Mohi Medical Services Ltd | Health & social care | 2012 |
| MS Proper Clean Limited | Administrative & support | 2015 |
| Msaa Properties Ltd | Real estate | 2020 |
| MSB London Properties LLP | | 2023 |
| MSG Business Limited | Other services | 2020 |
| MSJ Fire Ltd | Public administration | 2024 |
| Msjk Infinity Limited | Real estate | 2018 |
| MSP Ductwork Ltd | Construction | 2016 |
| MSP Finance Team Tax Ltd | Professional & scientific | 2023 |
| Mstr Academy Limited | Education | 2020 |
| Mstruct Ltd. | Information & communication | 2015 |
| MTS Homes & Developments Ltd | Construction | 2025 |
| Mudd Business Solutions Ltd | Professional & scientific | 2018 |
| Mudd Management Solutions Ltd | Construction | 2018 |
| Mudd Services Ltd | Construction | 2009 |
| Mudon Investments Limited | Real estate | 2021 |
| Mugurel Construction Ltd | Construction | 2017 |
| Muirhead Quay Limited | Real estate | 2021 |
| Muka Group Ltd | Information & communication | 2019 |
| Mulberry Bush Nursery and Pre-School Ltd | Education | 2022 |
| Multichoice Dental Laboratory Limited | Health & social care | 2000 |
| Multicom Computers Limited | Information & communication | 2001 |
| Multifarious Engineering Ltd | Professional & scientific | 2012 |
| Multiform Maintenance Limited | Real estate | 2011 |
| Mumbai Street Food & Falafel Ltd | Hospitality | 2023 |
| Munaminas Ltd | Households | 2024 |
| Munch MIX Cafe Ltd | Hospitality | 2026 |
| Munic Admin Services Limited | Administrative & support | 2016 |
| Munteanu Developments Limited | Construction | 2013 |
| Murphy Howard Property Limited | Real estate | 2026 |
| Musa and Ibrahim Limited | Real estate | 2026 |
| Musaamal Limited | Real estate | 2026 |
| Muscle & Manips Limited | Health & social care | 2007 |
| Musicvision Productions Limited | Information & communication | 2025 |
| Must Have Experiences Limited | Wholesale & retail | 2024 |
| Mustard Rainham Ltd | Hospitality | 2012 |
| Mustard Search and Selection Limited | Administrative & support | 2015 |
| MWR Group UK Ltd | Wholesale & retail | 2024 |
| MX4 Limited | Information & communication | 2000 |
| My Pet Adoption Limited | Other services | 2021 |
| My Tree Care Limited | Agriculture & fishing | 2016 |
| MYA Mills Limited | Arts & recreation | 2019 |