| Mandm Rainbow Solutions Limited | Health & social care | 2024 |
| Mane Attraction Hair Salon Limited | Other services | 2016 |
| Mangal BG Ltd | Transport & logistics | 2019 |
| Mangalia Ltd | Wholesale & retail | 2020 |
| Mann’S Lounge Limited | Hospitality | 2026 |
| Mano Carp Ltd | Agriculture & fishing | 2024 |
| Manor Building Developments Ltd | Real estate | 2024 |
| Manor Execs Limited | Real estate | 2025 |
| Manspeed | | 1996 |
| Mantle Panel Limited | Construction | 2001 |
| Mantus Building Services Ltd | Construction | 2023 |
| Mantus Properties Ltd | Real estate | 2025 |
| Manual Training Limited | Education | 2014 |
| Maplecote Limited | Wholesale & retail | 2021 |
| Maquint Consultant Limited | Information & communication | 2009 |
| MAR Car Services Ltd | Transport & logistics | 2018 |
| Mara Trans Ltd | Transport & logistics | 2018 |
| Maramu Services Ltd | Construction | 2015 |
| Marcbase Limited | Transport & logistics | 2019 |
| Marcella Global Ltd | Administrative & support | 2018 |
| Marcelo's and Charlie’S Ltd | Hospitality | 2025 |
| Marcin Michal Nowak Ltd | Transport & logistics | 2019 |
| Marcin Trans Ltd | Transport & logistics | 2025 |
| Marcnico Ltd | Real estate | 2015 |
| Mardyke Valley Golf Club Limited | Arts & recreation | 1992 |
| Marek WP Ltd | Transport & logistics | 2021 |
| Margaret James Investments Limited | Real estate | 2021 |
| Margate Properties Limited | Real estate | 2023 |
| Marian Airinei Ltd | Transport & logistics | 2024 |
| Marigold Healthcare Ltd | Health & social care | 2026 |
| Marina Leisure Ltd | Hospitality | 2026 |
| Mariolt Limited | Transport & logistics | 2014 |
| Marios Polishing Ltd | Wholesale & retail | 2023 |
| Marios WR Ltd | Wholesale & retail | 2020 |
| Marjo & Co Estates Ltd | Real estate | 2025 |
| Mark 5 Fashion Ltd | Wholesale & retail | 2017 |
| Mark Housing Limited | Real estate | 2021 |
| Mark Steadman Self Store Limited | Transport & logistics | 2012 |
| Marketing Mastery Group Ltd | Other services | 2019 |
| Markhams Contract Services Ltd | Construction | 2015 |
| Marks Gate Boxing Club C.I.C. | Arts & recreation | 2021 |
| Marksman Boxing Coaching Ltd | Arts & recreation | 2025 |
| Markus Tech Ltd | Information & communication | 2025 |
| Marlin Mechanical Services Ltd | Construction | 1995 |
| Marrjan Limited | Transport & logistics | 2014 |
| Mars Real Estate Ltd | Real estate | 2026 |
| Marsdon Consultancy Limited | Professional & scientific | 2022 |
| Marsher Properties Limited | Real estate | 2017 |
| Martello (Holdings) Limited | Financial services | 2016 |
| Martello Close Management Ltd | Real estate | 2018 |
| Martello Piling Limited | Construction | 2000 |
| Martial Arts World Basildon Ltd | Education | 2024 |
| Martial Arts World Brentwood Ltd | Education | 2024 |
| Martial Arts World Elite Ltd | Arts & recreation | 2022 |
| Martial Arts World Kicks for Kids Ltd | Education | 2024 |
| Martin Healy Limited | Professional & scientific | 2016 |
| Martin Mone T/A: Martin Mone Transport Limited | Water & waste | 2019 |
| Marvelcare Services Limited | Health & social care | 2022 |
| Marvellous Mastics Ltd | Construction | 2020 |
| Marvelous Light Limited | Professional & scientific | 2008 |
| Marvelous Light Services Limited | Professional & scientific | 2008 |
| Marvo Ltd | Transport & logistics | 2010 |
| Marvuka Ltd | Construction | 2019 |
| Mary-K Kare Ltd | Health & social care | 2015 |
| Marygold Luxury Ltd | Wholesale & retail | 2025 |
| Masaya Properties Ltd | Real estate | 2025 |
| Mash Convenience Store Ltd | Wholesale & retail | 2025 |
| Masons Carpentry & Joinery Ltd | Construction | 2016 |
| Masque Ltd | Transport & logistics | 2022 |
| Masss Enterprises Limited | Wholesale & retail | 2023 |
| Master Landscaping Ltd | Administrative & support | 2024 |
| Master Maths Tuition Ltd | Education | 2022 |
| Masterway GRG Ltd | Construction | 2016 |
| MAT Fire Protection Ltd | Public administration | 2025 |
| Matal Property Ltd | Real estate | 2023 |
| Matayagold International Ltd | Hospitality | 2022 |
| Mateos-Trans Ltd | Transport & logistics | 2020 |
| Material Managers Limited | Professional & scientific | 2021 |
| Mathias Home and Heart Limited | Administrative & support | 2025 |
| Matillens Agency Ltd | Manufacturing | 2021 |
| Matjo Property Developments Ltd | Real estate | 2025 |
| Matspeed Ltd | Transport & logistics | 2021 |
| Matteo Rosso Logistics Limited | Transport & logistics | 2016 |
| Matthias&Cosmin Limited | Transport & logistics | 2024 |
| Matushka Consultancy Limited | Information & communication | 2009 |
| Matusiak Ltd | Transport & logistics | 2019 |
| Maty Innovation Ltd | Construction | 2025 |
| Maty Logistics Ltd | Transport & logistics | 2020 |
| Matz Care Services Limited | Public administration | 2022 |
| Mavro Worldwide Community C.I.C. | Arts & recreation | 2023 |
| Mavro Worldwide Studios Ltd | Arts & recreation | 2025 |
| MAX Clenz Ltd | Extraterritorial | 2024 |
| Maxcat Ltd | Transport & logistics | 2023 |
| Maxvic Limited | Transport & logistics | 2026 |
| MAY Haulage Ltd | Transport & logistics | 2022 |
| Maya ST Property Ltd | Real estate | 2020 |
| Mayfountain Ltd | Health & social care | 2021 |
| Maymih Ltd | Transport & logistics | 2022 |
| Mayok UK Ltd | Real estate | 2020 |
| Maystar Building Services Ltd | Construction | 2018 |