| Mechanical Fireforce Ltd | Construction | 2019 |
| Mechgas Ltd | Construction | 2025 |
| Mecoy Holdings Limited | Real estate | 2019 |
| Mecoy Properties Ltd | Construction | 2020 |
| Medcert Ltd | Health & social care | 2019 |
| Medha Studies Limited | Education | 2021 |
| Media Icon Limited | Professional & scientific | 2000 |
| Media Vortex Limited | Information & communication | 2013 |
| Medicasa Ltd | Health & social care | 2013 |
| Medtom Limited | Transport & logistics | 2021 |
| Medzil Private Limited | Health & social care | 2021 |
| Meep Consulting Limited | Professional & scientific | 2022 |
| Meeran Ltd | Manufacturing | 2018 |
| Meeth Limited | Real estate | 2023 |
| MEG Associates Ltd | Construction | 2014 |
| MEG Lalabela Limited | Information & communication | 2014 |
| Mega Lume Limited | Wholesale & retail | 2026 |
| Mega-Heating Ltd | Construction | 2014 |
| Megalithomania Limited | Other services | 2016 |
| Megobprofessionalservices Ltd | Public administration | 2023 |
| Meleim Foods Ltd | Hospitality | 2022 |
| Meli's Landscaping Ltd | Administrative & support | 2023 |
| Melisa&Mitko Ltd | Wholesale & retail | 2025 |
| Memory Box UK Ltd | Professional & scientific | 2007 |
| Memory Share Box Limited | Professional & scientific | 2023 |
| Menad Training Services Ltd | Education | 2024 |
| Menbtl Ltd | Real estate | 2025 |
| Mercan Sales Limited | Wholesale & retail | 2025 |
| Mercers Haulage & Plant Hire Limited | Administrative & support | 2017 |
| Mercy Beauty Salon Ltd | Wholesale & retail | 2025 |
| Mercycare Private Ltd | Other services | 2019 |
| Meridian Zero Distribution Limited | Wholesale & retail | 2000 |
| Merk Logistics Limited | Transport & logistics | 2013 |
| Meronden Designs Limited | Construction | 1996 |
| Mers Construct Ltd | Construction | 2026 |
| Mert Altun Properties Ltd | Real estate | 2017 |
| Met-B Investments Limited | Real estate | 2023 |
| Meta Elite Build UK Limited | Construction | 2025 |
| Meta Mechanical Services Limited | Construction | 2021 |
| Metal and Waste Group Ltd | Financial services | 2021 |
| Metal and Waste Ltd | Water & waste | 2021 |
| Meterforce UK Limited | Real estate | 1998 |
| Method Consultants Limited | Professional & scientific | 2022 |
| Method Digital Agency Limited | Other services | 2021 |
| MF Flat Roofing Systems Ltd | Construction | 2022 |
| MFH Engineering Limited | Professional & scientific | 2015 |
| MG Advance Scaffolding Limited | Construction | 2024 |
| MG Car Body & Mechanical Repairs Ltd | Wholesale & retail | 2019 |
| MG Financial (London) Limited | Administrative & support | 2016 |
| MG H Partnership Ltd | Real estate | 2025 |
| MG Property Leases Ltd | Real estate | 2021 |
| Mg&Md Limited | Construction | 2019 |
| MGC Staff Solution Ltd | Administrative & support | 2022 |
| MGF Consultancy Ltd | Professional & scientific | 2009 |
| MGL (Essex) Ltd | Extraterritorial | 2017 |
| MGM Inter Services Ltd | Wholesale & retail | 2015 |
| MGM Mechanical Limited | Construction | 2021 |
| MGM Plumbing Limited | Construction | 2008 |
| MH Capital and Trading Limited | Professional & scientific | 2024 |
| MH Commercial Holdings Limited | Construction | 2022 |
| MH Concept Limited | Professional & scientific | 2017 |
| MH Consultants Ltd | Administrative & support | 2023 |
| MH Holdings Borough Market Reserves Limited | Construction | 2019 |
| MH Holdings Corporation (Union) Reserves Limited | Real estate | 2024 |
| MH Holdings Corporation Limited | Financial services | 2017 |
| MH Holdings Corporation London Reserves Limited | Real estate | 2022 |
| MH Holdings W1 Limited | Real estate | 2024 |
| MHB Electrical Limited | Construction | 2016 |
| Mhgb UK Ltd | Transport & logistics | 2017 |
| Mhlanga Healthcare Ltd | Health & social care | 2024 |
| MHP Development Limited | Construction | 2026 |
| MHS Radiators (Holdings) Limited | Professional & scientific | 2007 |
| MHS Radiators Limited | Wholesale & retail | 1984 |
| Michael Ebbsons Ltd | Professional & scientific | 2011 |
| Michael James Lashmar Ltd | Extraterritorial | 2025 |
| Michelle Murambatsvina Cares Ltd | Health & social care | 2023 |
| Micho-Amichi Limited | Transport & logistics | 2020 |
| Mick Twomey 13 Limited | Extraterritorial | 2014 |
| Mickyland Limited | Transport & logistics | 2018 |
| Micolli Films Limited | Transport & logistics | 2017 |
| Micromouse Ltd | Information & communication | 2012 |
| MID Essex Vision Limited | Health & social care | 2001 |
| Mide IT Limited | Information & communication | 2018 |
| Midrand Healthcare Limited | Health & social care | 2011 |
| Midway Maintenance Ltd | Construction | 2016 |
| Mighteesound Events Ltd | Hospitality | 2024 |
| Mighty Nimrods Property Maintenance Limited | Administrative & support | 2015 |
| Migogo Investments Ltd | Health & social care | 2010 |
| Miilolas Limited | Education | 2015 |
| Mikan Transport Limited | Transport & logistics | 2026 |
| Mikhel-Jay Services Limited | Health & social care | 2023 |
| Mikkycares Healthcare Limited | Health & social care | 2021 |
| Miko Interiors Ltd | Construction | 2016 |
| Miky Security Ltd | Administrative & support | 2020 |
| Mile Tally Pro Limited | Information & communication | 2025 |
| MILENIUM99 Ltd | Transport & logistics | 2023 |
| Miles Better Design Limited | Professional & scientific | 2010 |
| Mili Bears Ltd | Education | 2025 |
| Millheath Communications Limited | Construction | 1997 |
| Million Dollar MEN Ltd | Administrative & support | 2025 |