| MRW Pubs Limited | Wholesale & retail | 2018 |
| MRY Store Ltd | Wholesale & retail | 2025 |
| MS ACP Limited | Health & social care | 2023 |
| MS Engineering Consultancy Ltd | Administrative & support | 2015 |
| MS Holdings Group Limited | Financial services | 2021 |
| MS Property Management & Rental Ltd | Real estate | 2021 |
| MS Spray Project Limited | Other services | 2019 |
| MS Venture Properties Ltd | Real estate | 2017 |
| MSB Metrology Limited | Other services | 2018 |
| MSC Health Care Ltd | Health & social care | 2015 |
| MSH1 Ltd | Administrative & support | 2024 |
| MSJ Installations Limited | Construction | 2004 |
| MSM London Construction Materials Ltd | Wholesale & retail | 2020 |
| Msml Consultancy Ltd | Administrative & support | 2022 |
| MSN Marketing Limited | Other services | 2017 |
| Msnr Project Services Ltd | Administrative & support | 2026 |
| MSP OPS AI Ltd | Information & communication | 2026 |
| MSR Process Limited | Administrative & support | 2011 |
| MSV Radiology Limited | Other services | 2017 |
| MSZ Engineering Limited | Other services | 2017 |
| MT Civil Engineering Ltd | Administrative & support | 2025 |
| MT Commercial Consultancy Ltd | Professional & scientific | 2018 |
| MT High Tech Ltd | Professional & scientific | 2020 |
| MT Properties (Cheshire) Limited | Real estate | 2026 |
| MT Properties (NW) Ltd | Real estate | 2020 |
| Mtbms 2024 Ltd | Professional & scientific | 2001 |
| Mtbsmb Ltd | Hospitality | 2020 |
| MTC Franchise Group Ltd | Professional & scientific | 2024 |
| MTD Accounts Limited | Administrative & support | 2023 |
| Mten Design Limited | Administrative & support | 2024 |
| MTL Maritime Ltd | Education | 2020 |
| MTM Syndicate Ltd | Information & communication | 2017 |
| Mtmh Ltd | Real estate | 2021 |
| MTN1 Limited | Other services | 2022 |
| MTR Management Limited | Professional & scientific | 2024 |
| MTS Echelon Systems Ltd | Information & communication | 2026 |
| MTS Electrical Cheshire Ltd | Construction | 2021 |
| MTV Services Ltd | Construction | 2025 |
| Much Smarter UK Ltd | Education | 2021 |
| Muchie 1974 Limited | Administrative & support | 2024 |
| Mudman Outdoors Ltd | Professional & scientific | 2019 |
| Mughal Bros Limited | Administrative & support | 2016 |
| Muirwood Consultancy Ltd | Administrative & support | 2025 |
| Muka Works Ltd | Manufacturing | 2026 |
| Mukaway.Com Ltd | Water & waste | 2025 |
| Mukundi Limited | Public administration | 2019 |
| Mulberry Services Ltd | Professional & scientific | 2023 |
| Mullaney Consulting Ltd | Administrative & support | 2025 |
| Mulliner Estates Limited | Real estate | 2021 |
| Mulliner Financial Services Limited | Other services | 2017 |
| Multi Axis Solutions Ltd | Administrative & support | 2025 |
| Multi Weldmesh Limited | Manufacturing | 1985 |
| Multiplane Audio Limited | Administrative & support | 2026 |
| Multipli Consulting Limited | Professional & scientific | 2024 |
| Multiply Records Limited | Information & communication | 2010 |
| Multiskill Consultancy Limited | Administrative & support | 2014 |
| Multivohub Limited | Information & communication | 2026 |
| Multurnis Group Limited | Real estate | 2025 |
| Mulvaney Consulting Ltd | Professional & scientific | 2021 |
| Muma Estates Limited | Real estate | 2025 |
| Munawar Solutions Ltd | Administrative & support | 2026 |
| Munazul Ltd | Wholesale & retail | 2018 |
| Munro Creative Ltd | Administrative & support | 2023 |
| Munro Engineering Ltd | Administrative & support | 2017 |
| Munro Offshore Limited | Administrative & support | 2013 |
| Munstone Data Corporation Ltd | Information & communication | 2025 |
| Murphy Property Consultants Ltd | Professional & scientific | 2025 |
| Murphys Groundworks Ltd | Construction | 2024 |
| Murray Property Solutions Limited | Administrative & support | 2016 |
| Murraywood Construction Holdings Limited | Professional & scientific | 2016 |
| Murrell Properties Ltd | Hospitality | 2024 |
| Murrow Limited | Hospitality | 2009 |
| Musaharun Ltd | Hospitality | 2024 |
| Museum Street Property Management Ltd | Real estate | 2014 |
| Muskett Wealth Management Limited | Financial services | 2018 |
| Mustan IT Ltd | Information & communication | 2025 |
| Mutim Resources Ltd. | Administrative & support | 2016 |
| Muws Ltd | Information & communication | 2022 |
| MV Golf Ltd | Arts & recreation | 2017 |
| MV5S Consultancy Ltd | Information & communication | 2026 |
| Mvguk Ltd | Wholesale & retail | 2024 |
| MW CAD Services Limited | Administrative & support | 2011 |
| MW GEO Limited | Administrative & support | 2016 |
| MW Project Planning Limited | Administrative & support | 2024 |
| MWC Consultancy Limited | Professional & scientific | 2025 |
| MWK Consulting Limited | Professional & scientific | 2024 |
| Mwpm Consultancy Ltd | Information & communication | 2018 |
| Mwst VAT Consultancy Ltd | Professional & scientific | 2005 |
| MXC Consulting Services Ltd | Professional & scientific | 2025 |
| MXG Consulting Ltd | Information & communication | 2011 |
| My Aesthetics Educator Ltd | Education | 2022 |
| My Amazing Property Ltd | Real estate | 2025 |
| My Barber 1 Ltd | Other services | 2023 |
| My Boiler Quote Ltd | Construction | 2025 |
| My Business HQ Limited | Professional & scientific | 2014 |
| My CPD Provider Ltd | Education | 2020 |
| My Debt Manager Ltd | Financial services | 2019 |
| My Digital SAP Limited | Professional & scientific | 2016 |
| My Golf Tribe Ltd | Arts & recreation | 2021 |
| My GP Clinic Ltd | Health & social care | 2023 |