| Mediaflame Limited | Information & communication | 2025 |
| Medway Marine (UK) Ltd | Manufacturing | 2025 |
| Mehar Homes Ltd | Real estate | 2025 |
| Meilleure VIE Limited | Real estate | 2015 |
| Mejdani HCW Ltd | Administrative & support | 2020 |
| Meka Hair Design Limited | Other services | 2012 |
| Melanie Jane Mcgee Ltd | Information & communication | 2012 |
| Meliora Care & Education Ltd | Financial services | 2022 |
| Meraki Salon Limited | Other services | 2016 |
| Metfield Building Limited | Construction | 2014 |
| Metka (UK) Limited | Real estate | 2003 |
| Meva Co Lowestoft Ltd | Hospitality | 2024 |
| MF UK Foods Ltd | Real estate | 2021 |
| MG Builders (East Anglia) Limited | Construction | 2008 |
| MGE Finance Ltd | Financial services | 2019 |
| Mgpc Security & Training Limited | Administrative & support | 2025 |
| MHM Builders Limited | Construction | 2005 |
| Mhuk Services Limited | Construction | 2024 |
| MI GAS Limited | Professional & scientific | 2018 |
| Michael Chilvers Ltd | Professional & scientific | 2013 |
| Mick’S Munchbox Limited | Hospitality | 2025 |
| Mighty Minis Racing East Anglia Limited | Arts & recreation | 2026 |
| Mikeys Transport Ltd | Transport & logistics | 2025 |
| MILLER33 Limited | Construction | 2015 |
| Millie Rose Salon Limited | Other services | 2018 |
| Minds and Motion CIC | Arts & recreation | 2026 |
| Mirasis Ltd | Households | 2009 |
| Mirha Catering UK Ltd | Wholesale & retail | 2022 |
| Miss Wright Publishing Ltd | Information & communication | 2014 |
| Mitcham Management Fund | Households | 2002 |
| MJ Training East Ltd | Education | 2024 |
| MJH Aviation Consultancy Limited | Professional & scientific | 2025 |
| MJL Alpha Ltd | Real estate | 2025 |
| MJL Oilfield Services Ltd | Administrative & support | 2012 |
| MK Salon Ltd | Other services | 2024 |
| MK Springers | Arts & recreation | 2005 |
| ML Business Holdings Limited | Financial services | 2018 |
| MLD Architectural Design Ltd | Professional & scientific | 2024 |
| MLR Engineering Limited | Professional & scientific | 2015 |
| MM Change Limited | Information & communication | 2022 |
| Mmass Limited | Wholesale & retail | 1987 |
| MN Well-Child Support CIC | Education | 2020 |
| Mobbs Offshore Limited | Construction | 2018 |
| Mobile Phone Technology Ltd | Manufacturing | 2020 |
| Mobility Adapt East Ltd | Wholesale & retail | 2026 |
| Modu Management & Inspection Ltd | Professional & scientific | 2020 |
| Moelex Limited | Construction | 2015 |
| Moglet Ltd | Information & communication | 2022 |
| Mom’S Cash and Carry Ltd | Wholesale & retail | 2022 |
| Money Comms Limited | Information & communication | 2012 |
| Monosafe Limited | Real estate | 1988 |
| Moon ESQ Ltd | Other services | 2026 |
| Moore Management (East Anglia) Limited | Real estate | 2022 |
| Moore's Developments Limited | Construction | 2016 |
| Morgans Brewery Ltd | Extraterritorial | 2015 |
| Morse Holding (Lowestoft) Limited | Financial services | 2020 |
| Mortar and Money Ltd | Real estate | 2018 |
| Mortimer Property Holdings Ltd | Real estate | 2026 |
| Mortlock Properties Ltd | Real estate | 2022 |
| Moscow Scientific Industrial Association "Spectrum" | | 1994 |
| Moskinto UK Limited | Wholesale & retail | 2025 |
| Moss & Co (Holdings) Limited | Extraterritorial | 2012 |
| Moss & Co Properties Ltd | Real estate | 2026 |
| Moss & Co Trading Ltd | Hospitality | 2011 |
| Mount Estates London Limited | Real estate | 2017 |
| Mountain Peak Property Ltd | Real estate | 2023 |
| Move Easy Ltd | Construction | 2011 |
| Moyse Motors Limited | Wholesale & retail | 2016 |
| Mptp Construction Limited | Construction | 2017 |
| MR & MR Ltd | Other services | 2025 |
| MR Chips Kebab Ltd | Hospitality | 2025 |
| MR Smith Limited | Professional & scientific | 2007 |
| MR T'S Healthy Homes and Businesses Ltd | Administrative & support | 2018 |
| MRH Property Rental Limited | Real estate | 2021 |
| MS Lowestoft Limited | Real estate | 2024 |
| MS Primestores Private Limited | Wholesale & retail | 2026 |
| MTB 102 Trust | Arts & recreation | 1996 |
| Mulberry Medical Management Limited | Health & social care | 2015 |
| Mullit Limited | Arts & recreation | 2006 |
| Murdin Limited | Real estate | 2025 |
| Murdin Plant Ltd | Administrative & support | 2025 |
| MUS Barbers Ltd | Other services | 2025 |
| Musker Mcintyre & Clarke Ltd | Real estate | 2012 |
| Mutleycrew. Ltd | Extraterritorial | 2023 |
| MVK Properties Ltd | Real estate | 2010 |
| MWW Property Limited | Real estate | 2021 |
| My 4EVER Home Limited | Construction | 2025 |
| My Roofing Ltd | Construction | 2025 |
| Myana Ltd | Professional & scientific | 2017 |
| Myana Property Ltd | Real estate | 2019 |
| Myeasyroom Ltd | Real estate | 2022 |
| MYG (Maltings) Limited | Construction | 2025 |
| MYG Construction Limited | Construction | 2000 |
| MYG Servicing Limited | Construction | 2017 |
| Myheadshot Ltd | Professional & scientific | 2020 |
| N & G Enterprises Ltd | Education | 2025 |
| N & M Swim School Limited | Education | 2002 |
| N.&.M. (Oulton Broad) Limited | Real estate | 1965 |
| N.C.N.M. Accountancy Limited | Professional & scientific | 2018 |
| N.C.N.M. Limited | Professional & scientific | 2012 |