| Magnum Music Productions Ltd | Information & communication | 2024 |
| Maguire Funeral Directors Ltd | Other services | 2011 |
| MAH Precision Ltd | Professional & scientific | 2024 |
| Mahkota Hair Replacement Ltd | Other services | 2025 |
| Maia Retail Limited | Wholesale & retail | 2022 |
| Mailcoms Ltd | Manufacturing | 2006 |
| Majeda International Ltd | Hospitality | 2025 |
| Makeshift Motion Limited | Information & communication | 2015 |
| Makeup IS My Identity Ltd | Other services | 2016 |
| Malin Johannesson Ltd | Other services | 2017 |
| MAN Power Connections Ltd | Construction | 2017 |
| Mancave Master Barber Shop Limited | Other services | 2023 |
| Manderley Court Management Ltd | Households | 2007 |
| Mandgr Ltd | Hospitality | 2024 |
| Manison Holdings Limited | Financial services | 2020 |
| Manison Property Limited | Real estate | 2017 |
| Manjas Properties Limited | Households | 2021 |
| Manni Couriers Limited | Transport & logistics | 2016 |
| Mannkraft Aero Structures Integrity Ltd | Manufacturing | 2016 |
| Manor Court Healthcare Limited | Health & social care | 1992 |
| Mansma Ltd | Administrative & support | 2023 |
| Maple Resources Ltd | Construction | 2017 |
| Marches Assets Ltd | Real estate | 2018 |
| Marches Holdings Limited | Financial services | 2023 |
| Marches Property Group Ltd | Real estate | 2022 |
| Marfleet Holdings Ltd | Financial services | 2025 |
| Maria Rose Properties Limited | Real estate | 2024 |
| Marie Church Ltd | Other services | 2019 |
| Mark Biddle Limited | Manufacturing | 2018 |
| Mark Colebatch Management Limited | Administrative & support | 2007 |
| Marked One Tattoo Limited | Other services | 2017 |
| Market ST Barber Ltd | Other services | 2023 |
| Market Street Convenience Limited | Wholesale & retail | 2024 |
| Marquis Court Maintenance Limited | Households | 2003 |
| Marron Estates Ltd | Construction | 2023 |
| Marshall Bell Holdings Limited | Real estate | 2022 |
| Marshall Bell Limited | Construction | 1990 |
| Marshall Driveways Ltd | Construction | 2023 |
| Marshall Roofing Ltd | Construction | 2025 |
| Marshalls Building SE Limited | Construction | 2022 |
| Martindale Properties Limited | Real estate | 2015 |
| Martinne @ Face IT Aesthetics' Ltd | Other services | 2026 |
| Martyn Christian Limited | Professional & scientific | 2021 |
| Martyn Price Finance Limited | Real estate | 1996 |
| Marvin Properties Limited | Real estate | 2025 |
| Mason Design Ltd. | Professional & scientific | 2024 |
| Mason-Cole Holdings Limited | Real estate | 2011 |
| MAT the Brick Ltd | Construction | 2024 |
| Matekot Ltd | Health & social care | 2013 |
| Material Giant Ltd | Wholesale & retail | 2020 |
| Matt Clegg Systems Limited | Information & communication | 2012 |
| Matt Vale Claims Consultant Ltd | Financial services | 2016 |
| Mava Property Services Ltd | Real estate | 2023 |
| MAW Building Services Limited | Construction | 2006 |
| Maxim (GB) Limited | Wholesale & retail | 2004 |
| Maxim Business Support Ltd | Professional & scientific | 2025 |
| Maxwelding Ltd | Wholesale & retail | 2020 |
| MAY Towers Limited | Real estate | 2025 |
| Mayleo Ltd | Administrative & support | 2023 |
| Mazz Group Ltd | Financial services | 2025 |
| Mazz Stay Ltd | Real estate | 2026 |
| MB & KB Property Group Limited | Real estate | 2021 |
| MB Autobody Repairs Solutions Ltd | Wholesale & retail | 2025 |
| MB Engineering UK Limited | Professional & scientific | 2026 |
| MB Office Systems Limited | Administrative & support | 2009 |
| Mb&S Logistic Limited | Transport & logistics | 2020 |
| MC Dorset Limited | Wholesale & retail | 2019 |
| MC Seamless Guttering Limited | Construction | 2026 |
| MCG Refrigeration Ltd | Construction | 2022 |
| Mcmath Properties Ltd | Real estate | 2020 |
| MCR Carpentry & Roofing Limited | Construction | 2025 |
| MD Electrical Engineering Services Ltd | Construction | 2019 |
| MD Maintenance Services Ltd | Administrative & support | 2025 |
| MD Roofers Ltd | Construction | 2025 |
| MD Spotless Decor Ltd | Construction | 2024 |
| MDH Business Ltd | Hospitality | 2023 |
| MDS Property Services Ltd | Real estate | 2025 |
| ME and My Golf Limited | Wholesale & retail | 2012 |
| Meacham Residential Limited | Real estate | 2019 |
| Meakin Mover's Ltd | Water & waste | 2023 |
| Meals by Mitch Ltd | Information & communication | 2021 |
| Meandmysports Limited | Wholesale & retail | 2011 |
| Mechaniwire Limited | Manufacturing | 2011 |
| Mechinstall Limited | Construction | 2024 |
| Media Climate C.I.C. | Arts & recreation | 2010 |
| Mediacompare Limited | Professional & scientific | 2015 |
| Medicare Limited | Administrative & support | 2009 |
| Mediterranean Spice Limited | Hospitality | 2022 |
| Megacold Limited | Wholesale & retail | 2020 |
| Megatech Limited | Wholesale & retail | 1972 |
| Megi Motors Ltd | Wholesale & retail | 2024 |
| Mehercosmetics Ltd | Wholesale & retail | 2020 |
| Meif 6 Range Bidco Limited | Financial services | 2022 |
| Meif 6 Range Holdings Limited | Financial services | 2022 |
| Meif 6 Range Investments Limited | Financial services | 2022 |
| MEL Lucas Consulting Ltd | Professional & scientific | 2025 |
| Mel's Maxi Manes Limited | Other services | 2014 |
| Mellor & Co Group Limited | Financial services | 2024 |
| Mellor & Co Plastering Limited | Construction | 2018 |
| Mellor & Co Properties Ltd | Wholesale & retail | 2022 |