| Messina Trustees Limited | Real estate | 2009 |
| MET Film Limited | Information & communication | 2003 |
| MET Film Operations Limited | Administrative & support | 2010 |
| MET Film School Limited | Information & communication | 2008 |
| MET Media Limited | Professional & scientific | 2008 |
| Meta Partners Limited | Real estate | 2021 |
| Metado Ltd | Professional & scientific | 2014 |
| Metal Back Media Limited | Information & communication | 2019 |
| Metranet Communications Limited | Information & communication | 2003 |
| Metro Layered Limited | Information & communication | 2025 |
| Metro Standard Developments Limited | Construction | 2021 |
| Metro Storage (Angel) Limited | Administrative & support | 2014 |
| Metro Storage (Bayswater) Limited | Administrative & support | 2008 |
| Metro Storage (Tower Bridge) Limited | Administrative & support | 2020 |
| Metro Storage Holdings Limited | Administrative & support | 2016 |
| Metro Tend Limited | Information & communication | 2025 |
| Mettamustapha Limited | Other services | 2023 |
| MF Airconditioning Ltd | Construction | 2023 |
| MFJ Dental Limited | Health & social care | 2021 |
| Mfsys China Licence Management Company Limited | Professional & scientific | 2014 |
| Mfsys Global Shipping Licence Management Company Limited | Extraterritorial | 2014 |
| Mfsys Green Car Licence Management Company Limited | Professional & scientific | 2014 |
| Mfsys Hungary Licence Management Company Limited | Extraterritorial | 2014 |
| Mfsys Switzerland Licence Management Company Limited | Professional & scientific | 2014 |
| MG Premier Investments Limited | Other services | 2010 |
| MG Property Improvement Ltd | Real estate | 2020 |
| MGC Sussex Ltd | Wholesale & retail | 2021 |
| MGM Decorating Ltd | Construction | 2016 |
| MGM to Hand Ltd | Construction | 2019 |
| Mgode Limited | Health & social care | 2024 |
| Mgra (Steyning) Ltd | Households | 2024 |
| MH Participation Consultancy Limited | Professional & scientific | 2016 |
| Mhcoaching Limited | Arts & recreation | 2024 |
| MI Pregnancy Ltd | Professional & scientific | 2025 |
| Miacis Media Consultancy Limited | Professional & scientific | 2002 |
| Miah Bros MMA Gym Ltd | Arts & recreation | 2025 |
| Miasam Limited | Wholesale & retail | 2025 |
| Miastan Services Limited | Construction | 2019 |
| Mibri Group Ltd | Transport & logistics | 2018 |
| Michael Benedict Mccabe Limited | Arts & recreation | 2011 |
| Michael Bloomstein Precious Metals Ltd | Wholesale & retail | 2013 |
| Michael Paul Limited | Financial services | 1987 |
| Michael White Electrical Services Ltd | Construction | 2025 |
| Michaelhii Medical Limited | Health & social care | 2014 |
| Michella Oswald Events Ltd | Extraterritorial | 2018 |
| Michelle Tanner Funeral Directors Limited | Other services | 2009 |
| Micro Systems and Communications Limited | Information & communication | 1982 |
| Microbial Genomics Ltd | Professional & scientific | 2018 |
| Microfly Ltd | Manufacturing | 2025 |
| Micron Solutions Limited | Information & communication | 2018 |
| Microscape Employee Trustee Co. Limited | Professional & scientific | 2000 |
| Microscape Properties Ltd | Administrative & support | 2011 |
| Microscape Recruitment Group Limited | Financial services | 2016 |
| MID Antique Ltd | Wholesale & retail | 2023 |
| Middle KID Club Ltd | Wholesale & retail | 2026 |
| Middleton Grove Limited | Health & social care | 2017 |
| Midnight Communications Limited | Professional & scientific | 2017 |
| Midship Marine Consultancy Ltd | Professional & scientific | 2021 |
| Migeran Ltd | Information & communication | 2013 |
| Mike Freeman Development Limited | Information & communication | 2021 |
| Mikomax UK Ltd | Wholesale & retail | 2015 |
| Mila Elite Property Ltd | Construction | 2023 |
| Milan Groundworks & Civil Engineering Ltd | Construction | 2024 |
| Mildibee Limited | Wholesale & retail | 2018 |
| Mildly Official Ltd | Information & communication | 2025 |
| Mile.Eo Limited | Hospitality | 2022 |
| Mileoak Regeneration Limited | Construction | 2015 |
| Miles Building & Property Maintenance Ltd | Construction | 2025 |
| Miles Renos Limited | Construction | 2024 |
| Miletime Limited | Households | 1999 |
| Milford Grange (Storrington) Management Company Limited | Households | 2014 |
| Milk Marketing Ltd | Professional & scientific | 2024 |
| Mill House Group Investments Ltd | Financial services | 2013 |
| Millfield Estates Limited | Real estate | 1999 |
| Millington Carpentry & Construction Limited | Construction | 2024 |
| Million Creative Ltd | Information & communication | 2019 |
| Milly and JIN Ltd | Other services | 2020 |
| Millydale Ltd | Information & communication | 2013 |
| Milos XA Ltd | Hospitality | 2024 |
| Milton Ernest Hall Limited | Health & social care | 2025 |
| Mimi Locum Services Limited | Health & social care | 2013 |
| MIN04 Limited | Administrative & support | 2016 |
| Mina Mark Limited | Real estate | 2004 |
| Mind Body Dynamics Limited | Health & social care | 2023 |
| Mind Oxygen Limited | Education | 2015 |
| Mindful Extracts Ltd | Wholesale & retail | 2019 |
| MINE2MARKET Limited | Wholesale & retail | 2015 |
| Mining Association of the United Kingdom (the) | Other services | 1946 |
| Ministry on Third Ltd | Households | 2025 |
| Mint HR Solutions Ltd | Professional & scientific | 2017 |
| Mint Properties Limited | Real estate | 2003 |
| Misc Consulting Ltd | Information & communication | 2018 |
| Mishons Lettings Limited | Real estate | 2023 |
| Mishons Limited | Real estate | 2006 |
| Mispel Ltd | Wholesale & retail | 2020 |
| Miss Fallon DEE Ltd | Arts & recreation | 2015 |
| Miss P & D Interior & Exterior Decorators Limited | Other services | 2015 |
| Missrubyjewellery Ltd | Manufacturing | 2025 |
| Mistry Property Limited | Real estate | 2017 |
| Mitadoc Ltd | Health & social care | 2018 |