| Marginson Holdings Ltd | Financial services | 2022 |
| Maribogeaccounts Limited | Administrative & support | 2022 |
| Marie Charles Homes Ltd | Hospitality | 2026 |
| Marie Thorley Limited | Financial services | 2015 |
| Marina House Developments Limited | Professional & scientific | 2019 |
| Marine & Offshore Furniture Ltd | Manufacturing | 2013 |
| Marine Parade (Whitby) LLP | | 2020 |
| Mariners Arms Driffield Ltd | Hospitality | 2024 |
| Mariners Walk (Swansea) Apartment Management Company Limited | Households | 2016 |
| Mariners Walk (Swansea) Management Company Limited | Households | 2016 |
| Mario Cleaning Services Ltd | Administrative & support | 2012 |
| Marivicanna Ltd | Financial services | 2021 |
| Marjari Yoga Limited | Arts & recreation | 2026 |
| Mark Bollon Ltd | Professional & scientific | 2013 |
| Mark COX Transport Limited | Transport & logistics | 2020 |
| Mark Egan Advisory Ltd | Professional & scientific | 2022 |
| Mark Fairweather Groundworks Limited | Administrative & support | 2009 |
| Mark Horsley Limited | Administrative & support | 2002 |
| Mark Jenner & Co Limited | Professional & scientific | 2000 |
| Mark Langdale Ltd | Construction | 2002 |
| Mark Oglesby Sprayer Services Ltd | Agriculture & fishing | 2011 |
| Mark Otter Consultancy Ltd | Professional & scientific | 2019 |
| Mark Robinson Plumbing and Heating Ltd | Construction | 2016 |
| Mark Smith Electrical Limited | Construction | 2025 |
| Mark Stanton Ltd | Professional & scientific | 2026 |
| Mark Walford Racing Limited | Arts & recreation | 2023 |
| Mark Winters Leadwork & Roofing Ltd | Construction | 2017 |
| Markclair Homes Limited | Real estate | 2019 |
| Market Inside Limited | Professional & scientific | 2019 |
| Market Weighton Building Supplies Ltd | Wholesale & retail | 2014 |
| Market Weighton Hire Ltd | Administrative & support | 2024 |
| Market Weighton Leasehold Limited | Real estate | 2023 |
| Marketeers on Demand Limited | Extraterritorial | 2019 |
| Marketforce UK (Y2K) Limited | Professional & scientific | 1999 |
| Marketing Dynamics Consulting Limited | Administrative & support | 2025 |
| Marketing Edge Ltd | Professional & scientific | 2016 |
| Marketing Insight Limited | Professional & scientific | 2008 |
| Marketing Logistics Limited | Transport & logistics | 2009 |
| Markey Heritage & Co Ltd | Construction | 2025 |
| Markham Geopressure Services Ltd | Mining & quarrying | 2018 |
| Markham PR and Marketing Limited | Professional & scientific | 2020 |
| Markian Services Limited | Professional & scientific | 2014 |
| Markwell Developments Limited | Real estate | 2001 |
| Markwen Limited | Professional & scientific | 2017 |
| Marl Holdings Limited | Financial services | 2015 |
| Marla Bathrooms Ltd | Construction | 2025 |
| Marla Lettings Limited | Real estate | 2026 |
| Marley Homes (Alne) Ltd | Construction | 2025 |
| Marley Homes (Garth Grange) Ltd | Construction | 2024 |
| Marley Homes (Kelfield) Limited | Real estate | 2020 |
| Marlow Solutions Limited | Information & communication | 2007 |
| Marmar Holdings Ltd | Financial services | 2024 |
| Marmara Properties Limited | Real estate | 2023 |
| Maroon Consulting Ltd | Information & communication | 2025 |
| Marperton Limited | Administrative & support | 2002 |
| Marriott Homes Limited | Extraterritorial | 1963 |
| Marrkt Limited | Wholesale & retail | 2016 |
| Marsh and Thompson Ltd | Administrative & support | 2020 |
| Marsh Incorporation Ltd | Manufacturing | 2024 |
| Marshall & SON Window Cleaning Ltd | Administrative & support | 2021 |
| Marshall Agricultural Limited | Agriculture & fishing | 2019 |
| Marshall Auto Care Limited | Wholesale & retail | 2010 |
| Marshall Auto Parts Limited | Wholesale & retail | 2016 |
| Marshfield Ventures Limited | Administrative & support | 2010 |
| Marshgrove Ltd | Real estate | 2008 |
| Marshland House Management Company Limited | Households | 2016 |
| Marsland & Brierley Properties Ltd | Real estate | 2026 |
| Marston Design Limited | Construction | 2017 |
| Marston Lakes Ltd | Agriculture & fishing | 2025 |
| Marston Moor Marquees Ltd | Wholesale & retail | 2007 |
| Marston MOT Limited | Wholesale & retail | 2016 |
| Martello Park (Pembroke) Management Company Limited | Households | 2014 |
| Martha Longdon Consulting Ltd | Education | 2024 |
| Martin Baker Construction Management Ltd | Construction | 2024 |
| Martin Design Associates Limited | Professional & scientific | 2004 |
| Martin Herbert Limited | Arts & recreation | 2012 |
| Martin Jenkins Power Consulting Limited | Professional & scientific | 2007 |
| Martin Lush Consulting Ltd | Professional & scientific | 2022 |
| Martin Mangan Joinery Services Ltd | Construction | 2003 |
| Martin Services Limited | Real estate | 1988 |
| Martin Wells Electrical Limited | Construction | 1999 |
| Martin Wiltshire Consultancy Limited | Professional & scientific | 2026 |
| Martins of York Limited | Water & waste | 2004 |
| Martins Painting & Decorating Ltd | Construction | 2022 |
| Marton Associates Limited | Administrative & support | 2010 |
| Marton Modern Construction Solutions Ltd | Construction | 2023 |
| Martyn Rogers Woodturners Limited | Manufacturing | 2009 |
| Martyn Smith Limited | Professional & scientific | 2010 |
| Maru PK Ltd | Wholesale & retail | 2024 |
| Maru Resources Ltd | Professional & scientific | 2021 |
| Marvcat Media Limited | Professional & scientific | 2013 |
| Marway Properties Limited | Real estate | 2017 |
| Mary Nail Kingdom Ltd | Other services | 2023 |
| Marygate Mews (York) Management Company Limited | Households | 2023 |
| Maryhill Limited | Manufacturing | 1993 |
| Marzano Italian Ltd | Hospitality | 2024 |
| MAS Agricultural Services Ltd | Construction | 2021 |
| Masala Craft Limited | Hospitality | 2014 |
| Masala Craft R&B Limited | Hospitality | 2015 |
| Mascalls Grange (Paddock Wood) Residents Management Company Limited | Households | 2019 |