| Macair FMI Limited | Administrative & support | 1993 |
| Macdees Accountancy & Bookkeeping Limited | Professional & scientific | 2009 |
| Mach Two Limited | Administrative & support | 2003 |
| Machina Express Limited | Manufacturing | 2025 |
| Machique Limited | Professional & scientific | 2016 |
| Maclennan Waterproofing Ltd | Construction | 2020 |
| MAD Frog Industries Limited | Wholesale & retail | 2026 |
| Mady Trans Ltd | Transport & logistics | 2025 |
| Maebear Estates Ltd | Real estate | 2023 |
| Maebra Logistics Ltd | Transport & logistics | 2019 |
| Magdalen Metalwork Ltd | Manufacturing | 2017 |
| Magdalene Court Management Limited | Households | 2000 |
| Magellan House Residential Management Company Limited | Households | 2003 |
| Magic Carpets (Commercial) Ltd. | Construction | 1999 |
| Magic Castings Ltd | Arts & recreation | 2023 |
| Magik Systems Limited | Professional & scientific | 2002 |
| Magister Militum Limited | Manufacturing | 1993 |
| Magmoomer Limited | Construction | 2024 |
| Magna Foods Limited | Extraterritorial | 1996 |
| Magna Horses Limited | Other services | 2021 |
| Magna Learning Partnership | Education | 2011 |
| Magna Services Group Ltd | Construction | 2020 |
| Magorex Ltd | Wholesale & retail | 2015 |
| Magpie Marvels Limited | Wholesale & retail | 2017 |
| Maisy Care at Home Ltd | Health & social care | 2020 |
| Maja Acquisitions Ltd | Real estate | 2024 |
| Major Mods Limited | Wholesale & retail | 2021 |
| Majorcrafts Ltd | Wholesale & retail | 2011 |
| Makaha Consulting Ltd | Information & communication | 2013 |
| Make Mark Consultancy Ltd | Professional & scientific | 2020 |
| Makestation Projects Ltd | Manufacturing | 2023 |
| Makowski Associates Limited | Administrative & support | 2013 |
| Malaria Genetic Biocontrol Trust | Professional & scientific | 2025 |
| Malletts Close Management Limited | Households | 2003 |
| Mallory and Castor Limited | Extraterritorial | 2016 |
| Mals Consultancy Limited | Information & communication | 2023 |
| Malthouse Dog Boarding Ltd | Other services | 2022 |
| Mammoth Motors Ltd | Wholesale & retail | 2025 |
| Manadk Limited | Other services | 2023 |
| Managex Ltd | Professional & scientific | 2023 |
| Mandale Road Management Company Ltd | Real estate | 2015 |
| Mandarin 6 Limited | Hospitality | 2026 |
| Mandarin House Limited | Hospitality | 2025 |
| Mandy's Buddies Ltd | Other services | 2022 |
| Mani's Food Bar Limited | Hospitality | 2016 |
| Maniflow and Company Limited | Manufacturing | 1996 |
| Manor Farm (Coombe Bissett) Limited | Real estate | 1959 |
| Manor Farm (Denvilles) Management Company Limited | Households | 2013 |
| Manor Farm (Sixpenny Handley) Ltd | Agriculture & fishing | 2012 |
| Manor Farm Butchers (Wiltshire) Ltd | Wholesale & retail | 2013 |
| Manor Farm Interiors Limited | Manufacturing | 2022 |
| Manor Farm Management (Bishopstone) Limited | Households | 1998 |
| Manor Farm Nursery School Limited | Education | 2010 |
| Manor Farm Productions Ltd | Manufacturing | 2021 |
| Manor Grange Management Company Limited | Households | 2024 |
| Manor House Developments Ltd | Construction | 2021 |
| Manor Kingsway Management Company Limited | Administrative & support | 2014 |
| Manor Leys Management Company Limited | Households | 2020 |
| Manor Q Sourcing Ltd | Wholesale & retail | 2025 |
| Manorwood (Chilmark) Ltd | Manufacturing | 2018 |
| Mansion House Estates Limited | Construction | 1990 |
| Maple (221) Limited | Households | 2004 |
| Maple (243) Limited | Households | 2005 |
| Maple (328) Limited | Households | 2007 |
| Maple Asset Management Ltd | Real estate | 2025 |
| Maple House (Verwood) Management Company Limited | Households | 2021 |
| Maple Oak (Alton) Management Company Limited | Households | 2017 |
| Maple Walk Management Company (Liphook) Limited | Real estate | 2020 |
| Maple Walk Management Company Ltd | Households | 2025 |
| Maplecroft Management Company Limited | Households | 1986 |
| Maplewood (Salisbury) Limited | Construction | 2009 |
| Marathi 2 Limited | Professional & scientific | 2026 |
| Marble and Sand Care Ltd | Health & social care | 2025 |
| Marble in the Bottle Limited | Education | 2015 |
| Marblepark Limited | Information & communication | 2003 |
| Marcham Farms Limited | Agriculture & fishing | 1996 |
| Marchants LEA Management Limited | Households | 2019 |
| Marco MTS Enterprise Ltd | Real estate | 2024 |
| Mardy Girl Coffee Ltd | Hospitality | 2025 |
| Marham Park Management Company Limited | Households | 2018 |
| Maria Corporation Ltd | Hospitality | 2023 |
| Mariannesears Solutions Limited | Information & communication | 2017 |
| Marina Felicity Church | Extraterritorial | 2025 |
| Marine Based Electrics Ltd | Construction | 2022 |
| Marine Buying Consultancy Services Ltd | Professional & scientific | 2021 |
| Marine Ecological Solutions Limited | Professional & scientific | 2005 |
| Marine South East Limited | Professional & scientific | 2005 |
| Maritz Holdings Limited | Administrative & support | 2018 |
| Mark LEE Odonnell Limited | Extraterritorial | 2025 |
| Mark Robbins Carpets & Beds Limited | Wholesale & retail | 1999 |
| Mark Stone Car Sales Limited | Transport & logistics | 1972 |
| Mark Toppin Logistics Limited | Transport & logistics | 2016 |
| Mark Waters Painter & Decorators Limited | Construction | 2002 |
| Market Quarter (Tonbridge) Management Limited | Households | 2006 |
| Marketing ET AL Limited | Professional & scientific | 2002 |
| Marksglade Limited | Real estate | 1968 |
| Marlborough Court Basingstoke Management Limited | Households | 2008 |
| Marley & Jerome Make Ltd | Manufacturing | 2026 |
| Marley's Headshop Limited | Wholesale & retail | 2015 |
| Marlin Marquees Limited | Administrative & support | 2006 |