| Mektric Limited | Construction | 2021 |
| Melanoplus Ltd | Professional & scientific | 2025 |
| Melior Hospitality Ltd | Health & social care | 2025 |
| Melong Ltd | Professional & scientific | 2026 |
| Meow&Melt Ltd | Manufacturing | 2025 |
| Mepframe Limited | Professional & scientific | 2016 |
| Merrow Property Limited | Real estate | 2012 |
| Merrywood Commercials Limited | Wholesale & retail | 2012 |
| MGB Properties Limited | Real estate | 2002 |
| Microguard Ltd | Information & communication | 2026 |
| Mielso Ltd | Professional & scientific | 2026 |
| Migros Import & Export Limited | Manufacturing | 1998 |
| Miles Productions Ltd | Information & communication | 2025 |
| Minex Technologies Limited | Professional & scientific | 1996 |
| Minex Technology Group Limited | Manufacturing | 2016 |
| MIW Integrated Systems Ltd | Administrative & support | 2022 |
| MJH Developments Hayes Lane Limited | Construction | 2019 |
| MJS Private Finance Ltd | Financial services | 2015 |
| MLP Wealth Advisers Ltd | Financial services | 2022 |
| MLP Wealth Management Ltd | Financial services | 2004 |
| MO Cleaning Services Limited | Administrative & support | 2014 |
| Mobilitypluss Limited | Transport & logistics | 2023 |
| Modern Mortgage Solutions Limited | Administrative & support | 2008 |
| Modern Paws Ltd | Other services | 2025 |
| Modsols Property Limited | Administrative & support | 2016 |
| Modus CM Ltd | Professional & scientific | 2025 |
| Monsterkil Pest Control Ltd | Health & social care | 2018 |
| Morden Property Developments Ltd | Real estate | 2019 |
| Morgan-Faulkner Limited | Professional & scientific | 2010 |
| Mother 4NATURE Limited | Health & social care | 2013 |
| Moto 1 Limited | Manufacturing | 2016 |
| Mountever Foods Limited | Wholesale & retail | 2018 |
| Mountever Holdings Limited | Financial services | 2024 |
| Mountever Restaurants Limited | Hospitality | 2019 |
| Mountever Retail Limited | Wholesale & retail | 2016 |
| Mountever UK Limited | Wholesale & retail | 2011 |
| Mountgood Ltd | Real estate | 1997 |
| Mousse Design Ltd | Wholesale & retail | 2023 |
| MPE Plumbing & Heating Limited | Construction | 2025 |
| Mpss Holdings Limited | Real estate | 2020 |
| MR. Mouldings Ltd | Manufacturing | 2003 |
| Msbeats Ltd | Health & social care | 2023 |
| MSF Productions Ltd | Information & communication | 2019 |
| Msks Enterprises Ltd | Households | 2019 |
| MSL Surveying Limited | Professional & scientific | 2018 |
| Murus Books Ltd | Information & communication | 2024 |
| Muzical Publishing Limited | Information & communication | 2023 |
| Mwlk Limited | Hospitality | 2025 |
| Naami Investments Ltd | Real estate | 2020 |
| Nadura Limited | Real estate | 2015 |
| Naz's Barber Ltd | Other services | 2019 |
| Nelbro Group Limited | Health & social care | 2016 |
| Netsol Solutions Limited | Administrative & support | 2014 |
| New Gold Medal Limited | Hospitality | 2022 |
| New Haven Lettings Limited | Real estate | 2024 |
| New Roads Collective Limited | Information & communication | 2024 |
| Newmexican Ventures Limited | Hospitality | 2013 |
| Nexus 3 Limited | Construction | 2010 |
| NG Green Skin Limited | Other services | 2026 |
| NGA Limited | Administrative & support | 2000 |
| Nhiq Ltd | Wholesale & retail | 2020 |
| Nicholas Contracts Ltd | Construction | 2016 |
| Nick Wong Investments Limited | Financial services | 2023 |
| Nino Gaudiano Limited | Construction | 2020 |
| NJL Limited | Extraterritorial | 2012 |
| NKB Business Services Limited | Administrative & support | 2006 |
| NMB Accounting Limited | Professional & scientific | 2018 |
| NMC Systems Ltd | Professional & scientific | 2018 |
| Noavate Operations Limited | Professional & scientific | 2026 |
| Nomad Advisory Ltd | Professional & scientific | 2025 |
| Normanhurst Court (Sutton) Limited | Households | 1987 |
| North Downs Lets & Stays Ltd | Hospitality | 2025 |
| North Surrey Building Contractors Limited | Other services | 2017 |
| North-South Estates Ltd | Construction | 2003 |
| Northfield Trading Co. Limited | Wholesale & retail | 1984 |
| NPJ Properties Ltd | Real estate | 2017 |
| NR Surveying Ltd | Professional & scientific | 2013 |
| NRT Beta Limited | Extraterritorial | 2014 |
| NRT Building Services Group Limited | Construction | 1996 |
| NRT Electrical & Mechanical Limited | Extraterritorial | 2014 |
| NSB Consultants Ltd | Professional & scientific | 2022 |
| NSR Care Homes Ltd | Health & social care | 2017 |
| O.C.Detailing Ltd | Wholesale & retail | 2025 |
| Oaks Park Ltd | Hospitality | 2021 |
| Oaks Park Property Ltd | Real estate | 2024 |
| Oaktree IE Limited | Professional & scientific | 2024 |
| Odontocare Limited | Extraterritorial | 2007 |
| Office Anyplace Limited | Information & communication | 2004 |
| Office Enhance Limited | Professional & scientific | 2019 |
| OGH Properties Limited | Real estate | 2024 |
| Omega Electrical ( South East) Ltd | Construction | 2025 |
| Omega Services Limited | Manufacturing | 1993 |
| ON Air Dining Limited | Hospitality | 2014 |
| One Touch Investments Limited | Real estate | 2014 |
| Online Strength Coach Ltd | Health & social care | 2024 |
| Opel Holdings Limited | Professional & scientific | 2022 |
| Open Door Enterprises Limited | Hospitality | 1993 |
| Opstix UK Ltd | Hospitality | 2025 |
| Opulent Eatery Ltd | Hospitality | 2019 |
| Opulent Realty Limited | Real estate | 2000 |