| MEN & Women Ltd | Wholesale & retail | 2016 |
| Menigo Limited | Other services | 2024 |
| Menkul Ltd | Wholesale & retail | 2025 |
| Menopause Studio Ltd | Education | 2025 |
| Menopause Vitamin Company Ltd | Wholesale & retail | 2021 |
| Mentormeet Ltd | Administrative & support | 2023 |
| Meox Limited | Administrative & support | 2005 |
| Mercer-Darvesh Holdings Limited | Financial services | 2025 |
| Mercer-Darvesh Trading Limited | Wholesale & retail | 2025 |
| Merchant Projects (Ipswich) Ltd | Construction | 2007 |
| Merchant Projects (Redhouse) Limited | Construction | 2023 |
| Merchant Projects Limited | Professional & scientific | 2007 |
| Merchant Transport Limited | Transport & logistics | 2014 |
| Merchants of Berkshire Ltd | Construction | 2016 |
| Mercia Capital Management Limited | Financial services | 2023 |
| Mercia Partners Group Limited | Financial services | 2020 |
| Mercia Partners Limited | Real estate | 2020 |
| Mercipay Ltd | Information & communication | 2026 |
| Mercury Life Sciences Ltd | Administrative & support | 2026 |
| Mercyland Medics Ltd | Health & social care | 2022 |
| Merestead Limited | Professional & scientific | 2012 |
| Merged UK Ltd | Information & communication | 1995 |
| Merida and AVP Limited | Real estate | 2024 |
| Merida Investments Ltd | Real estate | 2021 |
| Meridian Handtools UK Limited | Administrative & support | 2019 |
| Meridian Infotech Services LP | | 2022 |
| Meridian Options Limited | Real estate | 2010 |
| Meridian Strategic Land Limited | Real estate | 2009 |
| Meriton Energy Partners Limited | Administrative & support | 2025 |
| Meriwether Limited | Wholesale & retail | 2016 |
| Merlewood Limited | Transport & logistics | 2016 |
| Merlin Mechanical Services Ltd | Professional & scientific | 2026 |
| Merlins Property Services Ltd | Extraterritorial | 2015 |
| Merribrooks Holdings Ltd | Financial services | 2026 |
| Merribrooks Homes Ltd | Real estate | 2025 |
| Merribrooks Property Developments Limited | Construction | 2023 |
| Merrick Partlow Limited | Information & communication | 2009 |
| Merrifields Care Home Limited | Health & social care | 2023 |
| Merriveen Limited | Administrative & support | 2009 |
| Merriveen Property Limited | Administrative & support | 2015 |
| Mervyn Lambert Plant Limited | Construction | 1987 |
| Mesekoda Ltd | Wholesale & retail | 2025 |
| Mesem Ltd | Real estate | 2024 |
| Meta Content Tech Ltd | Wholesale & retail | 2024 |
| Metabolic Essex Limited | Arts & recreation | 2025 |
| Metasaf International Limited | Information & communication | 2025 |
| Methods Engineering Limited | Professional & scientific | 2024 |
| Metis Holiday Homes Ltd | Hospitality | 2023 |
| Metosoft Limited | Information & communication | 2024 |
| Metropay Ltd | Administrative & support | 2017 |
| Metsatalu OU Holding Co Ltd | Financial services | 2023 |
| Mex-Homes Limited | Construction | 2005 |
| Meyers & Sons Ltd | Construction | 2018 |
| Meyers & Sons Suffolk Ltd | Construction | 2024 |
| MFE Accessories Limited | Wholesale & retail | 2013 |
| MFE Tech Ltd. | Other services | 2017 |
| MFH Repairs Ltd | Manufacturing | 2026 |
| MFL Taxis Limited | Transport & logistics | 2025 |
| MFO Legacy Holdings Ltd | Financial services | 2026 |
| Mg&E Consulting Ltd | Administrative & support | 2022 |
| Mgco Properties Limited | Real estate | 2018 |
| MGE & Sons Transport Ltd | Transport & logistics | 2024 |
| MGH Venture Capital Ltd | Financial services | 2023 |
| MGM Logistics ( U K ) Ltd | Transport & logistics | 2026 |
| MGM Muthu Hotels Limited | Hospitality | 2022 |
| MGM UK Hotels Holdings Limited | Hospitality | 2020 |
| MGM UK Housing and Estate Private Ltd | Real estate | 2019 |
| MGS - Molina Garage & Repair Solutions Limited | Wholesale & retail | 2025 |
| MH Capital Ventures Ltd | Information & communication | 2023 |
| MHS Enterprise Ltd | Hospitality | 2021 |
| MHS400 Limited | Arts & recreation | 2014 |
| MI Chaii Limited | Hospitality | 2020 |
| MI Energy Ltd | Construction | 2025 |
| Miab Security Limited | Administrative & support | 2011 |
| Mibar Tranz Global Connect Limited | Construction | 2025 |
| Michael Broughton (Holdings) Limited | Real estate | 2023 |
| Michael Broughton Limited | Construction | 1973 |
| Michael Martin Property Ltd | Construction | 2018 |
| Michael Richards (Ipswich) Limited | Other services | 2002 |
| Michael Taylor Search & Selection Ltd | Administrative & support | 2015 |
| Michaelson Transport Limited | Transport & logistics | 2016 |
| Mick Mills Management Limited | Arts & recreation | 2002 |
| Micron Windows (Newmarket) Limited | Construction | 1980 |
| Micy Ltd | Transport & logistics | 2019 |
| MID Suffolk & Essex Flyer Media Group Ltd | Professional & scientific | 2026 |
| MID Suffolk Accountancy Services Limited | Professional & scientific | 2004 |
| MID Suffolk Chamber of Commerce Ltd. | Other services | 2016 |
| MID Suffolk Taxis Limited | Transport & logistics | 2004 |
| Mid-Anglia Chamber of Commerce and Industry Limited | Other services | 1992 |
| Mid-Century Furniture UK Limited | Wholesale & retail | 2014 |
| Mid-Suffolk Equine Vets Ltd | Professional & scientific | 2023 |
| Midas Productions UK Ltd. | Administrative & support | 2000 |
| Middlemarch Films Limited | Information & communication | 1990 |
| Middleton Waste Services Ltd | Water & waste | 2018 |
| Middleweek Newton Limited | Arts & recreation | 2014 |
| Midii Entertainment Ltd | Arts & recreation | 2024 |
| Midland Steel Sections Limited | Professional & scientific | 1993 |
| Midnight Moon Ipswich Ltd | Wholesale & retail | 2021 |
| MIE Solutions Ltd | Information & communication | 2026 |
| Mieya Limited | Wholesale & retail | 2025 |