| MSS Motor Group Ltd | Wholesale & retail | 2021 |
| MSS Online Limited | Wholesale & retail | 2024 |
| MSS Performance Limited | Wholesale & retail | 2014 |
| MSS Racing Limited | Wholesale & retail | 2019 |
| Msvs Properties Limited | Real estate | 2020 |
| MSW Comfort Solutions Ltd | Construction | 2024 |
| MSW Shop House Limited | Wholesale & retail | 2024 |
| MSX International Limited | Administrative & support | 1985 |
| Msxi UK Limited | Financial services | 2007 |
| MT Coffee Ltd | Hospitality | 2018 |
| MT Global Ventures Ltd | Wholesale & retail | 2026 |
| Mtbg 2014 Limited | Professional & scientific | 2014 |
| Mtbg Limited | Professional & scientific | 2011 |
| MTS Invest Ltd | Construction | 2024 |
| Mubarti Limited | Information & communication | 2024 |
| Mugisha's Estates Limited | Real estate | 2026 |
| Muir Lane Estate Management Company Limited | Households | 2025 |
| Mulberry Bestir Ltd | Construction | 2024 |
| Mulberry Green Planning & Design Ltd | Construction | 2026 |
| Mulberry Installations Limited | Manufacturing | 2014 |
| Mulberry Publications Ltd | Information & communication | 1998 |
| Multi Language Hub Limited | Professional & scientific | 2022 |
| Multi-Finishing Ltd | Construction | 2015 |
| Multifix Carpentry & Construction Ltd | Construction | 2021 |
| Multimedia Economics Limited | Professional & scientific | 2015 |
| Multiple Sclerosis-Uk Limited | Health & social care | 1993 |
| Mumbai Mastee Ltd | Wholesale & retail | 2026 |
| Mumbo's Magic Ltd. | Professional & scientific | 2018 |
| Mumingroup Ltd | Wholesale & retail | 2025 |
| Munchbox Mummas Ltd | Hospitality | 2025 |
| Murapine Limited | Administrative & support | 1988 |
| Murataj Enterprise Limited | Administrative & support | 2018 |
| Murphy Smalls Kitchen Co Ltd | Hospitality | 2026 |
| Murrells & Co Accountants Limited | Professional & scientific | 2019 |
| Murrells Holdings Limited | Real estate | 2021 |
| Murrill Carpentry & Building Ltd | Construction | 2014 |
| Murton Developments Ltd | Real estate | 2024 |
| Murugu Limited | Health & social care | 2013 |
| Muscat Homes Limited | Real estate | 2016 |
| Musiso Ltd | Administrative & support | 2014 |
| Muspa EN Ltd | Hospitality | 2025 |
| Mussell IT Limited | Information & communication | 2018 |
| Musti Store Ltd | Wholesale & retail | 2025 |
| Musto Property Services Ltd | Real estate | 2024 |
| Muswell Rose Consulting Limited | Professional & scientific | 2023 |
| Muted Suit Limited | Professional & scientific | 2010 |
| Muthu & Milani Delivery Limited | Hospitality | 2023 |
| Mutleys Inc Ltd | Other services | 2011 |
| Muttley & Mabel Limited | Other services | 2022 |
| Mvhconsulting Limited | Professional & scientific | 2015 |
| Mvsc Investments Ltd | Wholesale & retail | 2026 |
| Mvsi Limited | Professional & scientific | 2019 |
| MW and H Ltd | Education | 2013 |
| MW Piling Services Ltd | Construction | 2019 |
| Mwjp Limited | Professional & scientific | 2013 |
| MWR Property Holdings Ltd | Real estate | 2024 |
| My Assisted Home Limited | Manufacturing | 2026 |
| My Home Choice (Essex) Limited | Health & social care | 2010 |
| My Home Choice (MID Essex) Limited | Health & social care | 2014 |
| My Icon Limited | Wholesale & retail | 2007 |
| My Mortgage Broker Limited | Administrative & support | 2014 |
| My Noodles Ltd | Hospitality | 2019 |
| My Place (Management) Limited | Real estate | 2011 |
| My Property Pros (Colchester) Limited | Administrative & support | 2026 |
| My Residency Ltd | Real estate | 2025 |
| My Trade Frame Limited | Construction | 2017 |
| My Vital Health Ltd | Health & social care | 2017 |
| MYA Aryan Limited | Real estate | 2019 |
| Mycosoul Ltd | Wholesale & retail | 2023 |
| Myland Diner Limited | Hospitality | 2026 |
| Myland Pre-School CIC | Education | 2013 |
| Myland Restorations Limited | Real estate | 2021 |
| Mynott Court Properties Limited | Households | 2002 |
| Myravi Consulting Ltd | Professional & scientific | 2024 |
| Myriad (a) Limited | Health & social care | 2022 |
| Myriad (E) Limited | Health & social care | 2022 |
| Myriad (G) Limited | Health & social care | 2022 |
| Myriad (L) Limited | Health & social care | 2022 |
| Myriad (O) Limited | Health & social care | 2022 |
| Myriad (P) Limited | Health & social care | 2022 |
| Myriad (T) Limited | Health & social care | 2022 |
| Myriad Group Limited | Health & social care | 2020 |
| Myriad Healthcare Holdings Limited | Professional & scientific | 2015 |
| Myriad Starlight Limited | Health & social care | 2022 |
| Myrtle Enterprises Limited | Administrative & support | 2004 |
| Myruby Limited | Administrative & support | 2005 |
| Mystarz Limited | Extraterritorial | 2022 |
| Mythic Skin Ltd | Wholesale & retail | 2020 |
| Mythos Consultant Limited | Wholesale & retail | 2014 |
| Mywai Ltd | Information & communication | 2026 |
| Myxcape Ltd | Manufacturing | 2019 |
| N & C Gold Buyers Limited | Wholesale & retail | 2011 |
| N & M Pizza’S and Indian Take Away Ltd | Hospitality | 2022 |
| N a Maxwell Consultancy Limited | Administrative & support | 2011 |
| N B Jessop Limited | Wholesale & retail | 2017 |
| N Burrows Ltd | Professional & scientific | 2013 |
| N Harrington Fencing Ltd. | Administrative & support | 2002 |
| N Last Utilities Limited | Energy | 2024 |
| N R Morgan Engineering Limited | Manufacturing | 2000 |
| N S Goodyear Ltd | Water & waste | 2012 |