| Main Digital Consulting Limited | Information & communication | 2025 |
| Mainstream Irrigation Limited | Administrative & support | 2004 |
| Maintenance Pro Sussex Limited | Construction | 2024 |
| Mairaa Hairstylist Ltd | Other services | 2025 |
| Maison Montiqué Ltd | Manufacturing | 2020 |
| Maisontison Ltd | Health & social care | 2025 |
| Maize Fields Ltd | Real estate | 2024 |
| Maja Trans Ltd | Administrative & support | 2020 |
| Majeks Group Limited | Health & social care | 2025 |
| Majestic Photo Company Ltd | Manufacturing | 2025 |
| Majhail & Sons Limited | Wholesale & retail | 2002 |
| Major Groundworks Ltd | Construction | 2018 |
| MAK Consultants Limited | Information & communication | 2024 |
| Makalo Driving School Limited | Education | 2021 |
| Make House Better Ltd | Construction | 2025 |
| Malazaar Shop Ltd | Wholesale & retail | 2023 |
| MALL47 Ltd | Hospitality | 2025 |
| Maltaward (Barriers) Limited | Construction | 2004 |
| Maltaward Limited | Extraterritorial | 2013 |
| Mama Gleam Limited | Administrative & support | 2024 |
| Mama's Indian Ltd | Hospitality | 2024 |
| Mamas UK Kitchen Ltd | Hospitality | 2024 |
| Mamemi Ltd | Public administration | 2026 |
| Mamoni Assets Ltd | Real estate | 2026 |
| MAN Refurbishment Projects Ltd | Extraterritorial | 2018 |
| Manage My Wealth Ltd | Financial services | 2019 |
| Management Pro PAY Limited | Administrative & support | 2026 |
| Mandala Street Food Limited | Hospitality | 2021 |
| Mandela African Food Grocery Ltd | Wholesale & retail | 2026 |
| Mane Barbers Limited | Other services | 2025 |
| Mane Market Limited | Wholesale & retail | 2023 |
| Mangat Impex Limited | Wholesale & retail | 2026 |
| Mango Rides Limited | Transport & logistics | 2023 |
| Mani Spark Ltd | Wholesale & retail | 2025 |
| Mankind Barber Pods Ltd | Administrative & support | 2019 |
| Mano Professional Services Ltd | Real estate | 2024 |
| Manor Dental Care Limited | Health & social care | 2010 |
| Manor House Beds Ltd | Wholesale & retail | 2016 |
| Manor Planting Ltd | Administrative & support | 2009 |
| Manor Royal Stores Ltd | Wholesale & retail | 2025 |
| Manosalwa Food Ltd | Hospitality | 2024 |
| Manotrans Limited | Transport & logistics | 2019 |
| Manrose Manufacturing Limited | Manufacturing | 1987 |
| Mansell Mctaggart Crawley Lettings Limited | Real estate | 2022 |
| Mansell Mctaggart Crawley Ltd | Real estate | 2007 |
| Mansell Recruitment Group Limited | Administrative & support | 1991 |
| Mansell Technical Services Limited | Professional & scientific | 1995 |
| Mansion House Recruitment Limited | Administrative & support | 1996 |
| Manta Energy & Marine Ltd | Professional & scientific | 2025 |
| Manta Foods Ltd | Hospitality | 2024 |
| Manykash Financial Limited | Financial services | 2020 |
| Manzanos Crawley Ltd | Wholesale & retail | 2021 |
| Maou's Urban Greenery Limited | Administrative & support | 2025 |
| Maple Car Parks Ltd | Transport & logistics | 2024 |
| Maple Heat Ltd. | Construction | 2019 |
| Maplecraft Home Improvements Limited | Construction | 2013 |
| Maplore Ltd | Information & communication | 2026 |
| Mapriori Limited | Information & communication | 2020 |
| MAQ Residential Ltd | Real estate | 2015 |
| MAR Client Services Limited | Financial services | 2026 |
| Marandi MV Limited | Transport & logistics | 2024 |
| Marbel Accounting Services Limited | Professional & scientific | 2016 |
| Marble Guard Limited | Administrative & support | 2025 |
| Marceau Limited | Wholesale & retail | 2025 |
| March Scopes UK Limited | Arts & recreation | 2011 |
| Marck Builder Construction Group Ltd | Construction | 2023 |
| Marck Import & Export Ltd | Wholesale & retail | 2025 |
| Marcos Services Ltd Ltd | Construction | 2018 |
| Marden Engineering Limited | Manufacturing | 2006 |
| Mare Couriers Ltd | Transport & logistics | 2018 |
| Marival Happy Clean Ltd | Administrative & support | 2024 |
| Mark Healthcare Private Ltd | Health & social care | 2017 |
| Mark J Hayes Limited | Construction | 2015 |
| Mark Woodland Consultant Ltd | Extraterritorial | 2021 |
| Marked 4 Care Ltd | Transport & logistics | 2021 |
| Market Enterprise Limited | Wholesale & retail | 2017 |
| Market Place Dental Practice Limited | Health & social care | 2006 |
| Marketaspect Ltd | Other services | 2023 |
| Markhz Limited | Wholesale & retail | 2022 |
| Marks DJ Limited | Information & communication | 2025 |
| Marlin Global Services Limited | Administrative & support | 2006 |
| Marnecio Ltd | Wholesale & retail | 2025 |
| Marquee Brothers Ltd | Professional & scientific | 2021 |
| Marry K Ltd | Wholesale & retail | 2024 |
| Mars Property Development Ltd | Real estate | 2018 |
| Martin W Smith Consulting Limited | Information & communication | 2012 |
| Marylebone Orthopaedic Casting Services Limited | Health & social care | 2016 |
| Mascalls Associates Limited | Administrative & support | 2016 |
| Mason Family Trustee Co. | Other services | 1979 |
| Massey Construction Services Limited | Construction | 2025 |
| Matei Express Ltd | Transport & logistics | 2020 |
| Matika Ltd | Transport & logistics | 2014 |
| Matin Promotions Limited | Professional & scientific | 2012 |
| Matrix for Environmental Services Limited | Wholesale & retail | 2016 |
| Matt and SAM Agencies Limited | Wholesale & retail | 2025 |
| Matt Davies Lighting Ltd | Arts & recreation | 2021 |
| Matt Fiddes Dojang LLP | | 2024 |
| Matthews Estates Limited | Real estate | 1970 |
| Matthews Roofing and Sons Ltd | Construction | 2021 |
| Maverick Coffee Company Ltd | Wholesale & retail | 2019 |