| Mattp Limited | Professional & scientific | 2015 |
| Matunos Ltd | Hospitality | 2014 |
| Matzliach Ltd | Real estate | 2010 |
| Maven 365 Ltd | Professional & scientific | 2022 |
| Mawson & Wareham (Music) Limited | Information & communication | 1969 |
| Maximus Holdings Ltd | Real estate | 2026 |
| Mayank Limited | Health & social care | 2024 |
| Mayfair Chauffeur Hire Limited | Administrative & support | 2025 |
| Mayfield Financial Planning Ltd | Financial services | 2015 |
| Maylight Ltd | Hospitality | 2023 |
| Maypine Construction Limited | Construction | 1973 |
| Maywells (NE) Limited | Arts & recreation | 2018 |
| Mazhar (Odds & Ends) Limited | Wholesale & retail | 2025 |
| Mazhar Ltd | Wholesale & retail | 2006 |
| Mazurkiewicz Estates Ltd | Real estate | 2019 |
| Maři Aurex Properties Ltd | Real estate | 2026 |
| MB Align, Restore and Invest Limited | Education | 2024 |
| MB Weld Tech Limited | Manufacturing | 2022 |
| MBG Investment Ltd | Real estate | 2023 |
| MBR (NE) Ltd | Real estate | 2024 |
| MBR Home Improvements Ltd | Other services | 2010 |
| MC Accounts Services Limited | Professional & scientific | 2021 |
| MC Circus Productions Limited | Arts & recreation | 2008 |
| MC Circus Shop Limited | Hospitality | 2022 |
| MC Electrical Management Services Ltd | Construction | 2024 |
| MC Seventy Limited | Real estate | 2021 |
| Mcbeth Support Services Ltd | Administrative & support | 2022 |
| Mcbride Property Solutions Limited | Real estate | 2019 |
| Mccready Page LLP | | 2007 |
| Mcdaniel & Co. Limited | Professional & scientific | 2010 |
| Mcelderry Technical Systems Ltd | Information & communication | 2018 |
| Mcgregor Contracting Services Limited | Information & communication | 2022 |
| Mcguire's Electrical Ltd | Professional & scientific | 2024 |
| MCM (Spain) Ltd | Real estate | 2016 |
| MCM Investments (UK & IRE) Ltd | Real estate | 2016 |
| Mcmanus Hall Ltd | Professional & scientific | 2012 |
| Mcmurray and Mcmurray Limited | Health & social care | 2016 |
| MCQ Training Limited | Education | 2019 |
| Mcvey Property Management Limited | Real estate | 2016 |
| MD Bookkeeping Service Ltd | Professional & scientific | 2010 |
| MD Private Finance Limited | Financial services | 2025 |
| MDB Property Maintenance NE Ltd | Construction | 2020 |
| MDE Referee Services Ltd | Arts & recreation | 2020 |
| MDF Joinery and Building Services Ltd | Construction | 2025 |
| MDL Holdings Ltd | Financial services | 2022 |
| MDR Associates Limited | Professional & scientific | 2024 |
| ME & Alan Limited | Information & communication | 2009 |
| MED Supplies Solutions Limited | Wholesale & retail | 2025 |
| Media Partnership Ltd | Information & communication | 2005 |
| Mediaworks Holdings Ltd | Financial services | 2019 |
| Mediaworks UK Limited | Information & communication | 2007 |
| Medibody Limited | Wholesale & retail | 2023 |
| Medical and Surgical Consulting Group Limited | Health & social care | 2021 |
| Medikarar Ltd | Health & social care | 2021 |
| Meeko Holdings Limited | Hospitality | 2020 |
| Meet EAT Share Ltd | Hospitality | 2023 |
| Megawatt Marine Limited | Professional & scientific | 2026 |
| Mehathoo Ltd | Wholesale & retail | 2026 |
| Meimei 88 Limited | Hospitality | 2022 |
| Mein Cycling Limited | Arts & recreation | 2022 |
| MEL Global Solutions Ltd | Manufacturing | 2026 |
| Melbourne Estates Ltd | Real estate | 2015 |
| Melbury (Ashington) Limited | Construction | 2022 |
| Meldrum Building Services Limited | Construction | 2018 |
| Meldrum Construction Services Group EOT Limited | Financial services | 2024 |
| Meldrum Construction Services Group Limited | Financial services | 2018 |
| Meldrum Construction Services Limited | Construction | 2001 |
| Meldrum Developments Ltd | Construction | 2015 |
| Meldrum Fire Engineering Limited | Professional & scientific | 2022 |
| Meldrum Homes Ltd Limited | Construction | 2015 |
| Meldrum Plant and Transport Limited | Construction | 2018 |
| Meldrum Structural and Civil Engineering Limited | Construction | 2018 |
| Melly's Carpets & Beds Ltd | Manufacturing | 2024 |
| Melorvale Limited | Real estate | 1999 |
| Melrose Welding & Inspection Services Ltd | Manufacturing | 2021 |
| Melvin Group Ltd | Administrative & support | 2024 |
| Memrouk Limited | Manufacturing | 2010 |
| Mendis Co Ltd | Health & social care | 2018 |
| Menthur Integrated Services and Technologies Limited | Extraterritorial | 2021 |
| Menuverse Ltd | Information & communication | 2023 |
| Mercantile Estates Ltd | Construction | 2001 |
| Mercantile Group Ltd | Real estate | 2026 |
| Mercantile Partnership Ltd | Construction | 2012 |
| Mercian Capital Holdings Limited | Financial services | 2025 |
| Meresyde Developments Ltd | Real estate | 2024 |
| Merifield Properties Limited | Extraterritorial | 1993 |
| Merrivale (Great Yarmouth) Limited | Arts & recreation | 1960 |
| Metallic Medical Ltd | Health & social care | 2023 |
| Metaltech Services Limited | Professional & scientific | 1984 |
| Meter Check UK Ltd | Professional & scientific | 2019 |
| Method Group Limited | Financial services | 2023 |
| Method Lounge Ltd | Education | 2026 |
| Method Valuation UK Limited | Administrative & support | 2014 |
| Metic Financial Ltd | Financial services | 2024 |
| Metic Group Ltd | Financial services | 2024 |
| Metrik Group Holdings Ltd | Financial services | 2025 |
| Metro Curls Ltd | Wholesale & retail | 2019 |
| Metro Motors NE Ltd | Wholesale & retail | 2022 |
| Metro Rental Limited | Real estate | 2005 |
| Metropolis Land & Property Developments Limited | Construction | 2018 |