| MBA Flue Services Limited | Construction | 2008 |
| MBB Maintenance Limited | Administrative & support | 2015 |
| Mbfwd Lighting Ltd | Construction | 2025 |
| Mbgw Limited | Information & communication | 2014 |
| MBT Developments Limited | Real estate | 2019 |
| MC 121 Football Coaching Ltd | Education | 2023 |
| MC 2023 Transports Ltd | Transport & logistics | 2023 |
| MC Property Services (Ipswich) Limited | Extraterritorial | 2005 |
| MC Roadlink Limited | Transport & logistics | 2025 |
| MC Transit Solutions Ltd | Transport & logistics | 2025 |
| Mccollin Engineering Limited | Construction | 2016 |
| Mccomb Limited | Construction | 2007 |
| Mccormack Electrical Services Ltd | Construction | 2020 |
| Mccormack Investment Holdings Ltd | Financial services | 2026 |
| Mccormack Properties Ltd | Real estate | 2026 |
| Mcdonald-Cameron Advisory Ltd | Professional & scientific | 2025 |
| MCE Enterprises Limited | Manufacturing | 2025 |
| Mchor Ltd | Hospitality | 2018 |
| Mcjm Limited | Professional & scientific | 2017 |
| Mckeary DRY Lining Limited | Construction | 2002 |
| Mckenzie Home Improvements Ltd | Construction | 2021 |
| Mcma Consulting Ltd | Professional & scientific | 2025 |
| Mcnamara Developments Limited | Construction | 2016 |
| MCT Auto's Limited | Wholesale & retail | 2018 |
| MCW Chicken Grill Limited | Hospitality | 2025 |
| Mcwf Bespoke Ltd | Manufacturing | 2022 |
| MD Lashes Ltd | Wholesale & retail | 2019 |
| MD Quality Ltd | Construction | 2021 |
| MD Tree Services Ltd | Agriculture & fishing | 2013 |
| MDD Revolution Limited | Wholesale & retail | 2025 |
| MDG Fireaway Ltd | Hospitality | 2020 |
| MDH Offshore Cable Services Ltd | Energy | 2026 |
| MDH Trading Ltd | Wholesale & retail | 2017 |
| MDP Haulage Ltd | Transport & logistics | 2026 |
| Mdroad Ltd | Transport & logistics | 2020 |
| MDT3001 Ltd | Hospitality | 2019 |
| MDV Software for Public Transport Ltd. | Wholesale & retail | 2011 |
| MDZ Consulting (Suffolk) Ltd | Professional & scientific | 2018 |
| MDZ Consulting (UK) Ltd | Professional & scientific | 2025 |
| Meadow Accounts Limited | Professional & scientific | 2013 |
| Meadow Valley Lodges Ltd | Real estate | 2019 |
| Meadow Valley Management Company Limited | Households | 1999 |
| Meadow View (Ipswich) Ltd | Construction | 2024 |
| Meadow View Sales Limited | Wholesale & retail | 2024 |
| Meadowsway Hadleigh Limited | Construction | 2024 |
| Meal Specialist Limited | Hospitality | 2020 |
| Meals 4 YOU Ltd | Hospitality | 2024 |
| Measom Services Ltd | Information & communication | 2019 |
| Measured Brilliance Ltd | Information & communication | 2012 |
| Measurepoint Holdings Limited | Real estate | 2017 |
| Measurepoint Ltd | Professional & scientific | 2012 |
| Meat East Anglia Trades (Ipswich) Limited | Education | 1987 |
| Mecelec Solutions Ltd | Construction | 2015 |
| Meddoccall Ltd | Professional & scientific | 2026 |
| Media Capital Management Limited | Administrative & support | 2013 |
| Media Search Incorporation Ltd | Other services | 2010 |
| Media Storm News Ltd | Information & communication | 2023 |
| Media Suffolk Company Limited | Professional & scientific | 2014 |
| Mediaclickx LLP | | 2023 |
| Mediaflow Limited | Information & communication | 2019 |
| Mediassist Solutions Limited | Administrative & support | 2025 |
| Medic Digital Limited | Health & social care | 2012 |
| Medical Device Market Research Ltd | Professional & scientific | 2020 |
| Medical Lamp Supplies Limited | Wholesale & retail | 1999 |
| Medicament Consultancy Limited | Professional & scientific | 2025 |
| Mediconsult International Limited | Professional & scientific | 2017 |
| Medifit Limited | Construction | 2025 |
| Medinfo Internet Limited | Extraterritorial | 1999 |
| Mediqal Health Informatics Limited | Information & communication | 2006 |
| Mediterranean Marvels Ltd | Wholesale & retail | 2024 |
| Mediterranean Shipping Company (UK) Limited | Transport & logistics | 1977 |
| Medline Healthcare Limited | Health & social care | 2017 |
| Medlog Limited | Transport & logistics | 2018 |
| Medora Property Holdings Ltd | Real estate | 2026 |
| Medvista Innovations UK Ltd | Extraterritorial | 2026 |
| Medway Rail Limited | Transport & logistics | 2018 |
| Meer Style Barber Ltd | Other services | 2024 |
| Meetcarli Ltd | Information & communication | 2025 |
| Meezan Leather Enterprise Limited | Wholesale & retail | 2024 |
| MEG Premium Integrated Services Ltd | Hospitality | 2022 |
| Megakare Ltd | Professional & scientific | 2019 |
| Megamart Traders Ltd | Wholesale & retail | 2025 |
| Mehar G Ltd | Wholesale & retail | 2025 |
| Mehmed I Mehmed Ltd | Wholesale & retail | 2014 |
| Mekh Properties Ltd | Real estate | 2021 |
| Melford Biolaboratories Limited | Manufacturing | 2011 |
| Melford Laboratories Limited | Manufacturing | 1986 |
| Melgarth Developments Limited | Real estate | 2005 |
| Melia Rowe Developments Ltd | Construction | 2022 |
| Meliora Evolve Ltd | Administrative & support | 2015 |
| Melioras Consulting Limited | Information & communication | 2014 |
| Melissa Ventures Ltd | Extraterritorial | 2016 |
| Melita Properties Limited | Real estate | 1998 |
| Meliz Cooks Limited | Information & communication | 2022 |
| Mellon Studio Ltd | Information & communication | 2023 |
| Melly's Medical Limited | Health & social care | 2026 |
| Melton House Properties Limited | Real estate | 1986 |
| Melton Podiatry Practice Limited | Health & social care | 2006 |
| Melville & Hatfield Limited | Financial services | 2015 |
| Memorixa Systems Ltd | Information & communication | 2026 |