| Magpies Developments Limited | Transport & logistics | 2011 |
| Mahiki Fashion Limited | Professional & scientific | 2018 |
| Mahnoora Ltd | Wholesale & retail | 2025 |
| Maid in Charnwood Limited | Administrative & support | 2023 |
| Maidflex Limited | Information & communication | 1993 |
| Main Designs Limited | Transport & logistics | 2022 |
| Main ST Property Ltd | Real estate | 2025 |
| Maine Investments Ltd | Real estate | 2020 |
| Mainstay Consulting Limited | Information & communication | 2013 |
| Maintspec Ltd | Professional & scientific | 2017 |
| Maise and Rose Ltd | Wholesale & retail | 2017 |
| Maison Bright Ltd | Wholesale & retail | 2025 |
| Maison Rose Property Limited | Real estate | 2023 |
| Majiga & Son's Company Ltd. | Extraterritorial | 2024 |
| Major Padel Club UK Ltd | Arts & recreation | 2024 |
| Major PC Holdings Ltd | Financial services | 2024 |
| Major Travels Global Limited | Administrative & support | 2020 |
| Major Walks Limited | Other services | 2023 |
| MAK Care Ltd | Health & social care | 2018 |
| Making Projects Work Ltd | Professional & scientific | 2007 |
| Makoni Business Operations Limited | Other services | 2024 |
| Makoni Design Limited | Professional & scientific | 2024 |
| Makoni Holdings Limited | Financial services | 2024 |
| Malcolm Walker Developments (Leicester) Limited | Real estate | 1975 |
| Maldon Investments Limited | Construction | 1964 |
| Malgo Properties Ltd | Real estate | 2023 |
| Mallard Joinery Ltd | Construction | 2022 |
| Maltby Investment Ltd | Wholesale & retail | 2025 |
| Maltone Engineering Services Ltd | Manufacturing | 2018 |
| Mamadoc CIC | Information & communication | 2025 |
| Mamadoc Health Ltd | Health & social care | 2020 |
| Mamo Welding Ltd | Manufacturing | 2020 |
| MAN With a Van Loughborough Limited | Transport & logistics | 2018 |
| Management Angles Ltd | Professional & scientific | 2007 |
| Management Angles Services LLP | | 2016 |
| Manchester Bridge Business School Limited | Education | 2026 |
| Mandalays Business Consultancy Ltd | Professional & scientific | 2016 |
| Mandarin Resource Ltd | Professional & scientific | 2019 |
| Manish Makes Things Ltd | Information & communication | 2022 |
| Mankind Hair Salon Ltd | Other services | 2012 |
| Mannocks Limited | Manufacturing | 2005 |
| Manor Farm Management Co. Limited | Households | 2026 |
| Manor House Lettings Limited | Real estate | 2025 |
| Manor Organic Farm Shop Limited | Wholesale & retail | 2010 |
| Manorvale Limited | Real estate | 1998 |
| Mansfield Site Services Limited | Manufacturing | 2024 |
| Manta RAY Campervans Ltd | Manufacturing | 2026 |
| Mantle Architecture Ltd | Professional & scientific | 2020 |
| Mapdraft Limited | Other services | 1996 |
| Maple Properties (UK) Ltd | Real estate | 2014 |
| Maplewell Developments Ltd | Real estate | 2015 |
| Maplewell Road Management Company Limited | Real estate | 2019 |
| Mapm Logistics Limited | Transport & logistics | 2021 |
| Maranatha Care Ltd | Health & social care | 2025 |
| Marble Link Services Ltd | Health & social care | 2015 |
| Marbleamber Limited | Professional & scientific | 2010 |
| Marbuild Property Solutions Limited | Administrative & support | 2014 |
| Marcato Direct Limited | Wholesale & retail | 2014 |
| Marcel Architectural Steel Craft Ltd | Manufacturing | 2020 |
| Marcol EOT Limited | Other services | 2025 |
| Marcol Limited | Administrative & support | 1980 |
| Mardare Logistic Support Ltd | Transport & logistics | 2018 |
| Margaret & Vivian Ltd | Other services | 2025 |
| Marios Pizza and Chicken Limited | Hospitality | 2018 |
| Mariusz Kwiaton Limited | Wholesale & retail | 2026 |
| Marizo Pizza Limited | Hospitality | 2025 |
| Mark Architecture Ltd | Professional & scientific | 2017 |
| Mark Beeby Limited | Education | 2007 |
| Mark Digby (Netherlands) Limited | Agriculture & fishing | 2007 |
| Mark Godwin Racing Limited | Professional & scientific | 2010 |
| Mark Kendrick and Sons Plumbing & Heating Ltd | Construction | 2015 |
| Mark Lennon Mechanical Site Services Limited | Professional & scientific | 2016 |
| Mark Nicholas Properties Limited | Real estate | 1999 |
| Mark R Wardley Limited | Extraterritorial | 2008 |
| Market Forever Ltd. | Professional & scientific | 2017 |
| Market Holdings Limited | Real estate | 2009 |
| Market Stop Gros Ltd | Wholesale & retail | 2025 |
| Marketing 4 Growth Limited | Information & communication | 2015 |
| Markham Property Group Limited | Real estate | 2021 |
| Marlborough Buildings Limited | Real estate | 1960 |
| Marle PIT Hill Ltd | Professional & scientific | 2023 |
| Marpave Limited | Administrative & support | 2013 |
| Marq-One Ltd | Professional & scientific | 2020 |
| Marra Investments Limited | Financial services | 2020 |
| Marsden Automotive Limited | Wholesale & retail | 2025 |
| Marsden Joinery Ltd | Manufacturing | 2026 |
| Marsence Ltd | Information & communication | 2024 |
| Marshall Business Consultancy Ltd | Professional & scientific | 2020 |
| Marshall-Banks Vending Services Limited | Wholesale & retail | 2004 |
| Martin Bown & Co Ltd. | Financial services | 1997 |
| Martin Clay Consultancy Limited | Professional & scientific | 2017 |
| Martin Lewis Design Ltd | Professional & scientific | 2020 |
| Martin Taylor Decorating Services Limited | Other services | 2009 |
| Martins Distribution (UK) Ltd | Wholesale & retail | 2023 |
| Marvic Ltd | Professional & scientific | 2019 |
| Marxman Limited | Manufacturing | 2011 |
| Masala Munch Ltd | Hospitality | 2024 |
| Masc Interiors Limited | Construction | 2025 |
| Masc Investments Ltd | Real estate | 2026 |
| Masoli Limited | Real estate | 2022 |