| Martins Bakery Ltd | Wholesale & retail | 2017 |
| Martlesham Heath Householders Limited | Other services | 1975 |
| Martlesham Pizza Ltd | Hospitality | 2024 |
| Martlesham Service Centre Limited | Wholesale & retail | 2010 |
| Martlet Global Ltd | Professional & scientific | 2025 |
| Martur Limited | Transport & logistics | 2024 |
| Martyn LEE Builders Limited | Construction | 2005 |
| Marvela Trading Limited | Wholesale & retail | 2025 |
| Mary's Paws Ltd | Transport & logistics | 2023 |
| Marydan Services Ltd | Administrative & support | 2018 |
| Maryhill Logistic Solutions Ltd | Transport & logistics | 2025 |
| Maryus Transport Ltd | Transport & logistics | 2022 |
| Marz Assets Ltd | Real estate | 2018 |
| MAS Media Ltd | Professional & scientific | 2025 |
| Mash Residential Limited | Real estate | 2021 |
| Mash Staffing Holdings Limited | Financial services | 2018 |
| Mash Staffing Limited | Professional & scientific | 2004 |
| Masha of India Limited | Hospitality | 2012 |
| Mashenka Holdings Limited | Financial services | 2026 |
| Masi Seafoods Ltd | Hospitality | 2025 |
| Mason Clean Work Limited | Administrative & support | 2025 |
| Mason Family Chiropractic Ltd | Health & social care | 2012 |
| Mason Maritime Consulting Limited | Professional & scientific | 2011 |
| Masonic Hall Ipswich Limited | Other services | 2009 |
| Masons Estates (East Anglia) Limited | Real estate | 2001 |
| Massive Hub Ltd | Wholesale & retail | 2025 |
| Masson Capital Limited | Real estate | 2023 |
| Master Shopfitting & Refrigeration Ltd | Manufacturing | 2024 |
| Master's House Holdings Limited | Real estate | 2021 |
| Masterlord Estates Limited | Real estate | 2004 |
| Masterlord Property Management Limited | Households | 2016 |
| Masterlord Yacht Management Limited | Real estate | 2014 |
| Masters Travel Ltd | Administrative & support | 2024 |
| Matchbox Q Limited | Administrative & support | 2000 |
| Matei Driving Ltd | Transport & logistics | 2016 |
| Material Change AD Limited | Energy | 2011 |
| Mathswithpeps Education Ltd | Education | 2018 |
| Matisa Woodbridge Ltd | Construction | 2016 |
| Matkha Limited | Wholesale & retail | 2023 |
| Matras Exporters Ltd | Wholesale & retail | 2021 |
| Matriarch Property Limited | Real estate | 2022 |
| Matt Carley Elite Group Coaching Limited | Education | 2024 |
| Matt Carpentry Ltd | Construction | 2017 |
| Matt Endeavours Limited | Agriculture & fishing | 2017 |
| Matt Porter Web Design Limited | Information & communication | 2006 |
| Matt's Maps and Repairs Ltd | Wholesale & retail | 2021 |
| Matt's ODD JOB Co Limited | Hospitality | 2025 |
| Matthew Caesar Limited | Professional & scientific | 2026 |
| Matthew Clemence Limited | Professional & scientific | 2024 |
| Matthew Douglas Limited | Financial services | 2003 |
| Matthew Stock Mortgage Solutions Ltd | Financial services | 2021 |
| Matticks Building Services Limited | Construction | 2021 |
| Maudland Ltd | Construction | 2019 |
| Mauka Developments Limited | Real estate | 2015 |
| Mauldons Limited | Financial services | 2026 |
| Maurice J Bushell & Co Limited | Professional & scientific | 2016 |
| Maustan Construction Limited | Administrative & support | 2005 |
| Mavam Community Limited | Health & social care | 2012 |
| Mavam Estates Limited | Real estate | 2013 |
| Mavam Group Limited | Administrative & support | 2012 |
| Mavam Supported Housing Limited | Health & social care | 2010 |
| Mavam Technical Services Limited | Information & communication | 2012 |
| Maven-Idea Ltd | Professional & scientific | 2016 |
| Mavensoft Ltd | Information & communication | 2025 |
| Mavis Pest Control Ltd | Administrative & support | 2020 |
| Mavnix Limited | Information & communication | 2019 |
| MAW Operations Ltd | Transport & logistics | 2026 |
| MAW Plumbing Services Limited | Construction | 2013 |
| MAX Mini Market Ltd | Wholesale & retail | 2018 |
| MAX Moto Ltd | Education | 2018 |
| Maxi Transport Ltd | Transport & logistics | 2024 |
| Maxies Manns Ltd | Hospitality | 2025 |
| Maxim Facilities Management Ltd | Administrative & support | 2010 |
| Maximotransports Ltd | Transport & logistics | 2025 |
| Maxwell Enki Limited | Professional & scientific | 2015 |
| May's Essentials Limited | Wholesale & retail | 2024 |
| Maya Trans Ltd | Construction | 2014 |
| Mayan Capital Limited | Financial services | 2023 |
| Mayburn Construction Ltd | Construction | 2026 |
| Mayes Fisheries Limited | Wholesale & retail | 2002 |
| Mayes Property Collective Limited | Real estate | 2025 |
| Mayilon Ltd | Professional & scientific | 2016 |
| Mayne Media Limited | Information & communication | 2015 |
| Mayonnaise on Left Ltd | Arts & recreation | 2018 |
| MAZ & Co Accountants Limited | Professional & scientific | 2004 |
| MAZ Trade Ltd | Wholesale & retail | 2022 |
| Mazarelo Sports Management Ltd | Arts & recreation | 2022 |
| Maze Logistic Solutions (Holdings) Ltd | Transport & logistics | 2020 |
| Maze Logistic Solutions Ltd | Transport & logistics | 2011 |
| Mazebright Limited | Real estate | 2025 |
| MB Housewares Ltd | Wholesale & retail | 2012 |
| MB Management Services Limited | Construction | 2015 |
| MB MAX Ltd | Administrative & support | 2024 |
| MB Optimal Solutions Ltd | Information & communication | 2017 |
| MB Paving & Landscaping Ltd | Administrative & support | 2021 |
| MB Speech Limited | Information & communication | 2003 |
| MB Sports Coaching Ltd | Education | 2026 |
| MB Towbars Ltd | Manufacturing | 2013 |
| MB Transportation Ltd | Transport & logistics | 2026 |
| MB Valeting Services (EA) Limited | Administrative & support | 2012 |