| Markelly Limited | Financial services | 2019 |
| Market Anatolia Ltd | Wholesale & retail | 2021 |
| Market EUE Ltd | Wholesale & retail | 2024 |
| Market Harborough Candle Co Ltd | Wholesale & retail | 2025 |
| Market Leads Limited | Professional & scientific | 2020 |
| Market Link Property Limited | Real estate | 2024 |
| Market Street Properties Limited | Real estate | 1991 |
| Market Vision Academy Ltd | Financial services | 2025 |
| MARKET8 Ltd | Wholesale & retail | 2024 |
| Marketing Chambers Limited | Real estate | 2019 |
| Marketing Voice Ltd | Professional & scientific | 2019 |
| Marketiviti Limited | Professional & scientific | 2026 |
| Marketplace Masters Ltd | Wholesale & retail | 2023 |
| Markfield (Leicester) Limited | Energy | 2011 |
| Markfield Consulting Limited | Professional & scientific | 2010 |
| Markfield Day Nursery Limited | Education | 1998 |
| Markfield Holdings Limited | Hospitality | 2024 |
| Markgenius Limited | Professional & scientific | 2014 |
| Markham Amber Ltd | Wholesale & retail | 2025 |
| Markhor Essentialz Ltd | Wholesale & retail | 2025 |
| Marko (Leicester) Ltd | Administrative & support | 2020 |
| Markon Groups Ltd | Wholesale & retail | 2023 |
| Markopolo Trans Ltd | Transport & logistics | 2013 |
| Marks and Marlow Limited | Administrative & support | 1979 |
| Marks Capital Ltd | Real estate | 2015 |
| Marks Electrical Group PLC | Financial services | 2021 |
| Marks Electrical Limited | Wholesale & retail | 2002 |
| Marks Properties (Leics) Limited | Real estate | 1911 |
| Marks Valeting Ltd | Administrative & support | 2025 |
| Markson Futures Ltd | Health & social care | 2026 |
| Marku Ltd | Administrative & support | 2018 |
| Markwise Limited | Other services | 2021 |
| Markwood Inc Limited | Real estate | 2024 |
| Marlborough Constructional Engineers Limited | Manufacturing | 1988 |
| Marlborough Property (Clapham) Limited | Real estate | 2016 |
| Marlborough Property (Eltham) Limited | Real estate | 2016 |
| Marlborough Property (Harley Street) Ltd | Real estate | 2021 |
| Marlborough Property (Kilburn) Limited | Real estate | 2016 |
| Marlborough Property (Pinner) Limited | Real estate | 2016 |
| Marlborough Property (Putney) Limited | Real estate | 2016 |
| Marlborough Property (Water Court) Limited | Real estate | 2013 |
| Marlborough Property (Watermead) Limited | Real estate | 2012 |
| Marlborough Property (Whetstone) Limited | Real estate | 2016 |
| Marlejac Limited | Health & social care | 2025 |
| Marlow Builders Limited | Construction | 1985 |
| Marlow Carpentry Ltd | Construction | 2017 |
| Marlow Construction Consultancy Ltd | Construction | 2024 |
| Marlow Creative Limited | Information & communication | 2014 |
| Marmin Ltd | Information & communication | 2012 |
| Marmon Lift Recruitment Ltd | Administrative & support | 2025 |
| Maroon Studios Ltd | Wholesale & retail | 2022 |
| Marpak Limited | Manufacturing | 1998 |
| Marpatt Limited | Wholesale & retail | 1977 |
| Marqs Sport Ltd | Wholesale & retail | 2020 |
| Marquess Estates Ltd | Real estate | 2017 |
| Marreem Ltd | Other services | 2026 |
| Marriomgrant Consult Limited | Professional & scientific | 2024 |
| Mars 27 Limited | Real estate | 2019 |
| Mars 30 Limited | Real estate | 2020 |
| Mars Care Services Limited | Health & social care | 2007 |
| Mars Knitwear International Limited | Manufacturing | 2018 |
| Mars Knitwear Limited | Real estate | 1994 |
| Mars Metallics Ltd | Construction | 2024 |
| Mars Perfume Ltd | Wholesale & retail | 2025 |
| Mars Software Limited | Information & communication | 2023 |
| Marsden Barn Trailers Ltd | Wholesale & retail | 2015 |
| Marsden Direct Group Limited | Professional & scientific | 2003 |
| Marsden Group Limited | Financial services | 1996 |
| Marsh & Company Holdings Limited | Financial services | 1995 |
| Marsh & Company Insurance Brokers Limited | Financial services | 1995 |
| Marshall Farms Limited | Extraterritorial | 2025 |
| Marshalls Traditional Chippy Ltd | Hospitality | 2023 |
| Marsol Limited | Wholesale & retail | 2025 |
| Marstone 66 Properties Ltd | Real estate | 2025 |
| Marstone Advisory Limited | Professional & scientific | 2026 |
| Marta Butik UK Ltd | Wholesale & retail | 2026 |
| Martech Technical Services Limited | Construction | 2006 |
| Marten Inn Limited | Hospitality | 2006 |
| Martha Close Management Company Limited | Professional & scientific | 2012 |
| Martin & Ferries Auction Ltd | Wholesale & retail | 2024 |
| Martin Abbott Limited | Wholesale & retail | 2015 |
| Martin Bros. Pizza Co. Ltd | Hospitality | 2018 |
| Martin Digital Limited | Information & communication | 2024 |
| Martin Kennedy (Blaby) Limited | Wholesale & retail | 2018 |
| Martin Taylor Truckin Ltd | Transport & logistics | 2013 |
| Martin's Directs Ltd | Wholesale & retail | 2025 |
| Martini Packaging Systems Limited | Manufacturing | 2002 |
| Martins (Leicester) Limited | Real estate | 1947 |
| Martins Construction Solutions Ltd | Construction | 2024 |
| Martins Cuisine Ltd | Hospitality | 2024 |
| Martins Property Company Limited | Real estate | 2021 |
| Martinside Services Ltd | Wholesale & retail | 2025 |
| Martpol Drive Ltd | Transport & logistics | 2021 |
| Martsark Cleaning Limited | Administrative & support | 2026 |
| Martyn James Asset Security Limited | Administrative & support | 2024 |
| Marula Marketing Ltd | Professional & scientific | 2026 |
| Maruti Aluminium Frames Ltd | Manufacturing | 2025 |
| Maruti Autoweld Ltd | Manufacturing | 2024 |
| Maruti Carshalton Ltd | Hospitality | 2024 |
| Maruti Coulsdon Ltd | Hospitality | 2024 |