| Mini Marvels PRE School C.I.C. | Education | 2010 |
| Miranet LLP | | 2023 |
| Mistley Thorn Limited | Hospitality | 2008 |
| Mizzi Plumbing & Electrical Limited | Construction | 2022 |
| MJB3 Productions Limited | Arts & recreation | 2026 |
| MJC European Ltd | Transport & logistics | 2018 |
| Mjcf Enterprise Limited | Construction | 2023 |
| MJV Horses Limited | Other services | 2025 |
| MKX Design Ltd | Information & communication | 2009 |
| Mlnn Ltd | Administrative & support | 2026 |
| Modus Architecture Limited | Professional & scientific | 2019 |
| MOI Interiors Limited | Extraterritorial | 2009 |
| Momentum Performing Arts Academy Ltd | Arts & recreation | 2018 |
| Monarch's Management Company Limited | Households | 2008 |
| Moneybox Financial Management Limited | Financial services | 2017 |
| Monkey Bizzness Adventure Play Limited | Arts & recreation | 2006 |
| Monkey Bunch Funky Munch Limited | Hospitality | 2024 |
| Monsoon Rochford Limited | Hospitality | 2023 |
| Monte Bracco Ltd | Administrative & support | 2012 |
| Montres Corum (UK) Limited | Wholesale & retail | 2000 |
| Morehaven Limited | Extraterritorial | 2017 |
| Morgan Ellis Lifts Ltd | Manufacturing | 2016 |
| Mortgage Plus (Essex) LLP | | 2009 |
| Mortgage Plus Thurrock Ltd | Financial services | 2019 |
| Mother and Baby Wellness Ltd | Health & social care | 2026 |
| MP Business Solutions Limited | Professional & scientific | 2025 |
| Mpaauk Ltd | Education | 2024 |
| MR. Pawfect Ltd | Other services | 2020 |
| Muddy Paws Club Limited | Other services | 2019 |
| Mudup Tackle Limited | Wholesale & retail | 2023 |
| Mulhouse Limited | Manufacturing | 1980 |
| Multi-Task Builders Ltd | Construction | 2012 |
| Murphy Collins Limited | Professional & scientific | 2024 |
| MV Reinforcement Ltd | Construction | 2014 |
| Mvrg Ltd | Real estate | 2024 |
| My Key Finance Limited | Financial services | 2014 |
| My Yogi Tribe Ltd | Arts & recreation | 2019 |
| Myla Estates Ltd | Real estate | 2024 |
| N L C Celebrant Limited | Other services | 2014 |
| Najtech Ltd | Information & communication | 2014 |
| Naliak Limited | Professional & scientific | 2026 |
| Namset Ltd | Professional & scientific | 2024 |
| Natural Objects Limited | Information & communication | 2000 |
| Nautical Noise Ltd | Arts & recreation | 2025 |
| Nautonomous Marine Limited | Professional & scientific | 2026 |
| Navi Kids Ltd | Wholesale & retail | 2025 |
| NBH Limited | Construction | 2019 |
| NC Chambers Limited | Administrative & support | 2024 |
| Neatwork Services Ltd | Administrative & support | 2023 |
| Neil Ryan Group Limited | Construction | 2019 |
| Nessa Estates 35 Limited | Real estate | 2019 |
| Nessa Estates Limited | Real estate | 2021 |
| Nestone Limited | Other services | 1978 |
| Nestone Securities Limited | Administrative & support | 1975 |
| Nevbright (8) Limited | Real estate | 1990 |
| Nevil Ellis Limited | Information & communication | 2004 |
| New Path Careers Limited | Information & communication | 2026 |
| New Targets Ltd | Professional & scientific | 2011 |
| Newcloud-It Ltd | Information & communication | 2024 |
| Newmed Healthcare Ltd | Health & social care | 2014 |
| Newsome Solutions Ltd | Information & communication | 2009 |
| Nex-Gen Flooring Ltd | Construction | 2025 |
| Nexus Group Developments Limited | Real estate | 2024 |
| NG Designs Limited | Professional & scientific | 2004 |
| Nice Monkey Limited | Wholesale & retail | 2009 |
| Niche Studios Limited | Professional & scientific | 2017 |
| Nicholls Law Group Limited | Professional & scientific | 2018 |
| Nick Austin Tune UP Ltd | Wholesale & retail | 2012 |
| Nigelpaine.Com Ltd | Other services | 2006 |
| Nignl Limited | Wholesale & retail | 2023 |
| NL Steelfixing Limited | Construction | 2012 |
| NLH Property Ltd | Construction | 2021 |
| Nmd-S Property Ltd | Real estate | 2019 |
| NMW Limited | Professional & scientific | 2025 |
| Noetik UK Limited | Professional & scientific | 2002 |
| Nolife Group Ltd | Wholesale & retail | 2026 |
| North END Shops Limited | Real estate | 2013 |
| Northern Sky Sauna Ltd | Manufacturing | 2026 |
| Northington Energy Centre Limited | Energy | 2019 |
| Nouvelle Properties Limited | Real estate | 1991 |
| NRP South Ltd | Construction | 2023 |
| NS Technology Solutions Ltd | Information & communication | 2018 |
| Nueva Vida Group Ltd | Real estate | 2022 |
| Nuwo Homes Limited | Real estate | 2023 |
| O a C Construction Limited | Construction | 2014 |
| Oakdene Autos Limited | Wholesale & retail | 2019 |
| Oakland Carpentry & Joinery Limited | Construction | 2005 |
| Oakstone Accounting Limited | Administrative & support | 2025 |
| Obea Construction Ltd | Construction | 2024 |
| Odani Engineering Ltd | Manufacturing | 2016 |
| Odysseus Management Solutions Ltd | Financial services | 2024 |
| Offshore Systems Engineering Limited | Professional & scientific | 2011 |
| OG Auto Care Limited | Wholesale & retail | 2025 |
| OK Contracting Solutions Ltd | Manufacturing | 2026 |
| Olas Communications Ltd | Information & communication | 2022 |
| Old Avenue Holdings Limited | Real estate | 2020 |
| Old Avenue NO.1 Limited | Real estate | 2014 |
| Old Bakehouse Enterprises Limited | Hospitality | 2009 |
| Old England Farms Ltd | Real estate | 2024 |
| Old Malt House Limited | Real estate | 2015 |