| Magic of Thailand Limited | Arts & recreation | 2016 |
| Magic&Unique Group Ltd | Arts & recreation | 2020 |
| Magna Fitness Ltd | Wholesale & retail | 2020 |
| Magnic Limited | Real estate | 2007 |
| Magnolia Projects Ltd | Administrative & support | 2019 |
| Magnur SPV1 Limited | Administrative & support | 2014 |
| Magnusian Ltd | Professional & scientific | 2025 |
| Mahe Capital Limited | Real estate | 2025 |
| Mahion Products Ltd | Wholesale & retail | 2023 |
| Mahlon Limited | Other services | 2012 |
| Mahonburgh Ltd | Construction | 2016 |
| Maicoon Tech Limited | Information & communication | 2018 |
| Maidenhead Roofing & Building Ltd | Construction | 2016 |
| Main Flooring & Interiors Ltd | Wholesale & retail | 2021 |
| Makalu Properties Ltd | Construction | 2017 |
| Makan - James Ltd | Construction | 2023 |
| Makara Marine Aqua Ltd | Agriculture & fishing | 2023 |
| Make and Trade Limited | Hospitality | 2012 |
| Makola Group Ltd | Financial services | 2022 |
| Malafi Ltd | Education | 2024 |
| Malan Enterprises Limited | Hospitality | 2023 |
| Mallinson Peake Limited | Arts & recreation | 2017 |
| Malwa Plant Training Ltd | Administrative & support | 2018 |
| MAM Carpentry & Joinery Ltd | Manufacturing | 2019 |
| Management Consulting Services Limited | Information & communication | 2022 |
| Mannyconstruction Limited | Construction | 2020 |
| Manor Advisors Ltd | Administrative & support | 2023 |
| Manor Carpets Ltd | Wholesale & retail | 2026 |
| Manor Farm Butchers Limited | Wholesale & retail | 2017 |
| Manor Kebab UK Ltd | Hospitality | 2024 |
| Manor Patisserie Ltd | Wholesale & retail | 2022 |
| Manors Food Ltd | Hospitality | 2023 |
| Mansat Ltd | Professional & scientific | 2015 |
| Mantra Design London Limited | Arts & recreation | 2018 |
| Mantra Healing Art Ltd | Arts & recreation | 2024 |
| Mantram Limited | Hospitality | 2015 |
| Mapchoo Ltd | Hospitality | 2021 |
| Maple Carpentry Hertfordshire Ltd | Manufacturing | 2023 |
| Marazion Limited | Information & communication | 2020 |
| Marble Arch Properties London Ltd | Real estate | 2017 |
| Marco Plumbing Ltd | Construction | 2010 |
| Marhaba Cricket India Ltd | Information & communication | 2023 |
| Maria Rose Estates Limited | Real estate | 2025 |
| Marie Carter Limited | Education | 2009 |
| Marina Imports Ltd | Administrative & support | 2025 |
| Marinepro Repair&Parts Co., Ltd | Wholesale & retail | 2025 |
| Mark Adams Healthcare Ltd | Health & social care | 2020 |
| Mark Film Limited | Construction | 2022 |
| Marketaccess.Tv Limited | Arts & recreation | 2013 |
| Marksol Ltd | Professional & scientific | 2022 |
| Marku Builders Limited | Construction | 2017 |
| Marlo Tech Ltd | Information & communication | 2020 |
| Marlow Court Ruislip Freehold Management Limited | Households | 2011 |
| Marlow Investments Ltd | Real estate | 2022 |
| Marquee Organisation Limited | Administrative & support | 1967 |
| Mars Cricket Limited | Manufacturing | 2010 |
| Marsia Ltd | Extraterritorial | 2019 |
| Martin Developments and Property Services Ltd | Real estate | 2019 |
| Masari Consultancy Limited | Professional & scientific | 2020 |
| Mashre Ltd | Information & communication | 2019 |
| Mass Solutions Limited | Information & communication | 2010 |
| Master Accordions London Ltd | Wholesale & retail | 2026 |
| Master Building Solutions Ltd | Construction | 2010 |
| Mastercare Contractors Limited | Construction | 2014 |
| Masterfix Roofing Ltd | Construction | 2018 |
| Masterhithe Limited | Real estate | 2016 |
| Masternak Ltd | Construction | 2013 |
| Maths Masters Ltd | Education | 2025 |
| Mati Collective Ltd | Professional & scientific | 2025 |
| Matmck Ltd | Professional & scientific | 2020 |
| Matteo Bartolini Consulting Ltd | Professional & scientific | 2022 |
| Matteo's Cucina Italiana Ltd | Hospitality | 2021 |
| Matthew 5:16 Ltd | Information & communication | 2024 |
| Maverick Business Academy London Ltd | Education | 2019 |
| Mawsad Health Care Ltd | Health & social care | 2022 |
| Maxim Holding Ltd | Extraterritorial | 2015 |
| Maximm Limited | Construction | 2018 |
| Maximunch 9 Ltd | Wholesale & retail | 2021 |
| Maximunch Limited | Wholesale & retail | 2016 |
| Mayagr Ltd | Real estate | 2023 |
| Maybate Limited | Information & communication | 2020 |
| Mayfair Decorators Limited | Construction | 2012 |
| Mayfair Export UK Ltd | Wholesale & retail | 2017 |
| Mayfair Manufacturing Ltd | Wholesale & retail | 2023 |
| Mayne GAS Plumbing & Heating Limited | Construction | 2019 |
| Mays DNB Ltd | Construction | 2021 |
| Mays UK Properties Ltd | Real estate | 2025 |
| MB Consult Ltd | Professional & scientific | 2022 |
| MB Properties Investment Limited | Real estate | 2019 |
| Mbdl Limited | Professional & scientific | 2011 |
| MBL Interpreters Limited | Administrative & support | 2008 |
| MC Grory Trade Ltd | Wholesale & retail | 2026 |
| MC Sports Equipment Ltd | Wholesale & retail | 2012 |
| MCJ Property Ltd | Real estate | 2018 |
| Mckenzie Homes Limited | Real estate | 2022 |
| Mckenzie Property Holdings Ltd | Real estate | 2017 |
| Mclarenstunts Limited | Arts & recreation | 2016 |
| MCM Hair Ltd | Other services | 2013 |
| MCM Roofing & Building Limited | Construction | 2020 |
| Mcmurdie Bathrooms Ltd | Construction | 2015 |