| Marcadivad Ltd | Hospitality | 2024 |
| Marcatrin Limited | Construction | 1979 |
| Marcel Housing Investments Ltd | Real estate | 2024 |
| Marcel Watkins Partnership Limited | Professional & scientific | 2006 |
| MARCEL’S1992PAINTING & Decorating Ltd | Construction | 2025 |
| March Bridal Ltd | Manufacturing | 2025 |
| March Developments Property Developers Ltd | Construction | 2016 |
| March Hare Bristol Limited | Other services | 2016 |
| Marcheur Services Limited | Administrative & support | 2017 |
| Marchwey Motor Centre Limited | Wholesale & retail | 2007 |
| Marcie Bower Designs Limited | Administrative & support | 2022 |
| Marcjr Ltd | Health & social care | 2025 |
| Marcliff Services Limited | Wholesale & retail | 2009 |
| Marcol Consultancy Limited | Professional & scientific | 2012 |
| Marcotte Ltd | Other services | 2020 |
| Marco’S Barbering Lounge Ltd | Other services | 2025 |
| Marcus Blaisdell Ltd | Administrative & support | 2021 |
| Marcus Farrow Bespoke Carpentry Limited | Manufacturing | 2015 |
| Marcus Olliff Period Property Services Limited | Construction | 1996 |
| Marcus Sampson Agricultural Services Limited | Wholesale & retail | 2025 |
| Marcus Stone Associates Ltd. | Professional & scientific | 1992 |
| Marcussen Consulting LLP | | 2005 |
| Marcussen Limited | Professional & scientific | 2001 |
| Marcussen Services Ltd | Professional & scientific | 2014 |
| Marden Power Limited | Energy | 2015 |
| Mardi Media Limited | Arts & recreation | 2008 |
| Mardyke House Management Company Limited | Households | 2006 |
| Maretron Limited | Manufacturing | 2024 |
| Mareze Ltd | Administrative & support | 2020 |
| Margaret Dixon Limited | Professional & scientific | 2020 |
| Margin Media Limited | Professional & scientific | 2009 |
| Marhup Ltd | Transport & logistics | 2019 |
| Mari Serviceco Limited | Financial services | 2025 |
| Mari UK Earl Limited | Financial services | 2025 |
| Mari UK Fractal Holdings Limited | Financial services | 2025 |
| Mari UK Holdings Limited | Financial services | 2025 |
| Mari UK Spanish Holdings Limited | Financial services | 2025 |
| Mari UK Topspin Holdings Limited | Financial services | 2025 |
| Maria Awan Ltd | Construction | 2024 |
| Maria Gros Orasanu Ltd | Health & social care | 2018 |
| Maria Pardo Picazo Ltd | Health & social care | 2022 |
| Maria Peters Associates Ltd | Education | 2013 |
| Maria-Cristina Culita Ltd | Wholesale & retail | 2014 |
| Marian-Alexandru Ltd | Transport & logistics | 2017 |
| Mariana Ciuca Consultancy Ltd | Professional & scientific | 2020 |
| Maria’S Dog Corner Ltd | Wholesale & retail | 2026 |
| Maricruz Dolado Interior Design Ltd | Professional & scientific | 2023 |
| Marie Gonzatto Reflexology Ltd | Extraterritorial | 2022 |
| Marie Healthcare Services Ltd | Health & social care | 2015 |
| Marie Talbot Consulting Limited | Professional & scientific | 2014 |
| Marie-Lou Therapy Ltd | Health & social care | 2024 |
| Marie-Scott Investments Ltd | Other services | 2026 |
| Marienberg IT Limited | Information & communication | 2018 |
| Marilok LP | | 2011 |
| Marimar Services Ltd | Wholesale & retail | 2023 |
| Marin Express Limited | Other services | 2019 |
| Marina & Islands Holding Limited | Financial services | 2022 |
| Marina Consult Limited | Information & communication | 2016 |
| Marina Gardens (Fishponds) Management Company Limited | Households | 1981 |
| Marina Lawrence Limited | Health & social care | 2019 |
| Marine Audit Services Ltd | Extraterritorial | 2018 |
| Marine Blue Limited | Construction | 2014 |
| Marine Parade Music Ltd | Information & communication | 2004 |
| Marine Project Services (UK) Ltd | Transport & logistics | 2013 |
| Marine Services Company Limited | Professional & scientific | 2002 |
| MARINE360 Ltd | Manufacturing | 2026 |
| Marinemax Superyachts UK Limited | Financial services | 2019 |
| Mariner Securities Limited | Financial services | 2010 |
| Mariners Hotel Limited | Hospitality | 2019 |
| Mariners House Limited | Households | 1992 |
| Marines Beans Ltd | Manufacturing | 2025 |
| Marinezone Limited | Real estate | 2002 |
| Mario Cafe & Lounge Ltd | Hospitality | 2025 |
| Mario's Coffee Ltd | Wholesale & retail | 2022 |
| Mario's Grub Ltd | Hospitality | 2018 |
| Mario's Property Inveestments Ltd | Real estate | 2022 |
| Mariola's Angels Ltd | Administrative & support | 2018 |
| Mariposa ( South West) Limited | Real estate | 2021 |
| Maris Films Ltd | Information & communication | 2023 |
| Maritime Events Ltd | Professional & scientific | 2007 |
| Marizon Limited | Households | 1972 |
| Mari’S Couture Ltd | Manufacturing | 2026 |
| Marj Infinity UK Limited | Financial services | 2026 |
| Marj&Khan Optics Ltd | Health & social care | 2022 |
| Marjs Improvement Limited | Administrative & support | 2019 |
| Mark 1 Machinery Repair Limited | Manufacturing | 2023 |
| Mark 2 Joinery Limited | Manufacturing | 2010 |
| Mark Aldridge Painting and Decorating Services Ltd | Construction | 2023 |
| Mark and MAY Ltd | Professional & scientific | 2018 |
| Mark and Stone Services Limited | Other services | 2020 |
| Mark Baker Limited | Extraterritorial | 2024 |
| Mark Bebbington Transport Limited | Transport & logistics | 2008 |
| Mark Bressington Limited | Construction | 2014 |
| Mark Cameron Poland Limited | Professional & scientific | 2022 |
| Mark Chippindall and Associates Limited | Professional & scientific | 2003 |
| Mark Collcutt Design Limited | Professional & scientific | 2006 |
| Mark Dando Associates Ltd | Professional & scientific | 2004 |
| Mark Dobie Ltd | Construction | 2016 |
| Mark Eboy Events Ltd Limited | Arts & recreation | 2018 |
| Mark Fazakerley (VHO) Limited | Health & social care | 2010 |