| Mainstream Staff Supplies Limited | Administrative & support | 2007 |
| Mainstream Training Limited | Education | 1997 |
| Maintainly! Limited | Administrative & support | 2024 |
| Maintech Management Ltd | Professional & scientific | 2015 |
| Maisey Homes LLP | | 2020 |
| Maisey Property Ltd | Real estate | 2020 |
| Maison Dieu Road Management Company Limited | Households | 2026 |
| Maison Militaire Ltd. | Wholesale & retail | 2015 |
| Majesty Transports Limited | Transport & logistics | 2024 |
| Makadama Ltd | Transport & logistics | 2020 |
| Makaria Ltd | Wholesale & retail | 2025 |
| Making a Difference to Maidstone | Wholesale & retail | 2015 |
| Making Miracles | Education | 2014 |
| Makoro Facilities Limited | Financial services | 2026 |
| Maldon Carbody Limited | Wholesale & retail | 2005 |
| Malica Property Limited | Real estate | 2024 |
| Malling Developments Limited | Construction | 2021 |
| Malling Flowers Limited | Wholesale & retail | 2025 |
| Malling Maintenance Ltd | Construction | 2014 |
| Malling PCN Ltd | Health & social care | 2021 |
| Malling Plant Hire Limited | Administrative & support | 2021 |
| Malling Utilities Ltd | Construction | 2026 |
| Malmot Ltd | Transport & logistics | 2023 |
| Malthouse & River Lodge Management Limited | Extraterritorial | 1997 |
| Malthouse Carpentry Limited | Construction | 2020 |
| Malvern Grange Investments Ltd | Construction | 2022 |
| Malzaly Care Limited | Health & social care | 2014 |
| MAM & Scott Services Limited | Other services | 2010 |
| Mama TEE African Food Ltd | Wholesale & retail | 2026 |
| Mamba Business Solutions Limited | Professional & scientific | 2022 |
| Managed Technology Corporation Topco Limited | Financial services | 2024 |
| Management 34 Limited | Households | 2003 |
| Manak Estates Ltd | Real estate | 2022 |
| Manak Solutions Ltd | Information & communication | 2013 |
| Manakamana Security Ltd | Administrative & support | 2025 |
| Mancave (Maidstone) Limited | Other services | 2018 |
| Manchester Appliances Outlet Limited | Wholesale & retail | 2018 |
| Manchester Garments (UK) Limited | Wholesale & retail | 2011 |
| Mandalov 83 Ltd | Transport & logistics | 2014 |
| Mani Assets Ltd | Real estate | 2025 |
| Manifestation Grafix Limited | Construction | 2014 |
| Mann Construction Management Ltd | Professional & scientific | 2024 |
| Mannvit UK Ltd | Professional & scientific | 2009 |
| Manol and SON Ltd | Other services | 2018 |
| Manor Construction and Fire Ltd | Construction | 2019 |
| Manor Fields (Maidstone) Management Company Limited | Households | 2004 |
| Manor Homes (South East) Limited | Construction | 2004 |
| Manor Homes (South Eastern) Ltd | Real estate | 2026 |
| Manor House Magazines Ltd | Administrative & support | 2008 |
| Manorplan Holdings Limited | Financial services | 2022 |
| Manorplan Limited | Professional & scientific | 2022 |
| Manortouch Limited | Construction | 1997 |
| Mansion Farm Group Limited | Construction | 2020 |
| Mansouri Design Solution Ltd | Professional & scientific | 2015 |
| Manuel Consulting Limited | Professional & scientific | 2025 |
| Manx Ninja UK Limited | Information & communication | 2026 |
| Manyways Limited | Professional & scientific | 1994 |
| Manzana Bidco Limited | Financial services | 2016 |
| Manzil Developments Ltd | Financial services | 2019 |
| Maple Leaf Campers Ltd | Manufacturing | 2019 |
| Maple Leaf Home Improvements Limited | Construction | 2023 |
| Maple Leaf Limited | Health & social care | 2015 |
| Maple Residents Company Limited | Households | 1972 |
| Marboss Ltd | Wholesale & retail | 2018 |
| Marcomms Group Limited | Professional & scientific | 2006 |
| Marcos Investments Limited | Real estate | 2021 |
| Marcus Joy Limited | Extraterritorial | 1999 |
| Marcus Wareing Limited | Financial services | 2008 |
| Marcus Wareing Restaurants Limited | Hospitality | 2008 |
| Mardale Tiling Contractors Limited | Construction | 2008 |
| Marden Garage Ltd | Wholesale & retail | 2015 |
| Mardia Ltd | Transport & logistics | 2020 |
| Marev Delivery Services Ltd | Transport & logistics | 2024 |
| Margaret Hartley Medical Ltd | Health & social care | 2021 |
| Marhusar Services Limited | Construction | 2021 |
| Marian-Ciombi Ltd | Construction | 2021 |
| Marianjjltrans Ltd | Transport & logistics | 2025 |
| Marien Ltd | Health & social care | 2019 |
| Marietta Strasoldo Garden Design Ltd | Administrative & support | 2014 |
| Marina Estates Limited | Hospitality | 1985 |
| Marina Park Homes Limited | Hospitality | 1987 |
| Marindoticlothing Ltd | Manufacturing | 2025 |
| Marine Care Surveyors Limited | Transport & logistics | 2003 |
| Marine View Kent Ltd | Hospitality | 2020 |
| Marino Bespoke Interiors Ltd | Manufacturing | 2015 |
| Marion Property Investments Limited | Real estate | 2021 |
| Mark Banbury Flooring Limited | Construction | 2014 |
| Mark Daniels Designs Ltd | Professional & scientific | 2021 |
| Mark Forsyth Admin Services Limited | Administrative & support | 2015 |
| Mark Gasson Building Services Ltd | Construction | 2023 |
| Mark Ranger Property Group Ltd | Real estate | 2025 |
| Mark Silvester Limited | Administrative & support | 2003 |
| Mark Stroud Building Services Ltd | Construction | 2014 |
| Marketinc Limited | Wholesale & retail | 2020 |
| Marketing Astro Ltd | Professional & scientific | 2024 |
| Marketing Manager Ltd | Professional & scientific | 2019 |
| Markets and Events UK Ltd | Wholesale & retail | 2024 |
| Marks Property Maintenance Ltd | Construction | 2025 |
| Marley Management Resource Limited | Professional & scientific | 2026 |
| Marlin Science Solutions Limited | Professional & scientific | 2023 |