| Mindful BEE Limited | Health & social care | 2022 |
| Mirza Reeder Group Ltd | Construction | 2012 |
| MJ Broad Estates Limited | Real estate | 2025 |
| MJ Parris Consulting Ltd | Other services | 2020 |
| MJ Supply Ltd | Manufacturing | 2019 |
| MJR Automotive Diagnostics Ltd | Wholesale & retail | 2024 |
| MK Software and Solutions Limited | Information & communication | 2025 |
| Mkfs Investments Ltd | Real estate | 2025 |
| MLC VA Services Ltd | Professional & scientific | 2021 |
| Mo's Specialist Cars Limited | Wholesale & retail | 2022 |
| Mobile Bar Hire & Sales Limited | Hospitality | 2011 |
| Moments of Calm Limited | Other services | 2025 |
| Moovoo Limited | Real estate | 2026 |
| Moreprint Ltd | Manufacturing | 2012 |
| Morris & Sons Fencing Ltd | Construction | 2019 |
| Moss King Associates Limited | Administrative & support | 2015 |
| Mote Park Watersports Centre Ltd | Arts & recreation | 2018 |
| Mote Taxis Ltd | Transport & logistics | 2025 |
| Mountfield Storage Solutions Limited | Administrative & support | 2024 |
| Moyofolu Limited | Administrative & support | 2012 |
| MP Players Ltd | Wholesale & retail | 2024 |
| Mpaf Services Ltd | Construction | 2023 |
| MPC Civil Engineering Solutions Ltd | Construction | 2015 |
| MPD Models Ltd | Wholesale & retail | 2024 |
| Mpwc Holdings Limited | Arts & recreation | 2025 |
| MRA Capital Limited | Administrative & support | 2017 |
| Mseleku Limited | Health & social care | 2019 |
| MST Aligned Ltd | Other services | 2025 |
| MTH Projects Ltd | Construction | 2026 |
| MTL Global Ltd | Wholesale & retail | 2006 |
| MTL Group Holdings Ltd | Wholesale & retail | 2021 |
| MTL Tech UK Limited | Information & communication | 2014 |
| Muddy Puddles Early Years Limited | Education | 2018 |
| Murphys Civil & Surfacing Ltd | Construction | 2026 |
| Must Have Ideas Group Ltd | Wholesale & retail | 2021 |
| Must Have Ideas Ltd | Administrative & support | 2018 |
| Mvdriveways Ltd | Construction | 2023 |
| My-Intuition Ltd | Professional & scientific | 2022 |
| Mykah Limited | Wholesale & retail | 2023 |
| N H Plumbing & Heating Solutions Ltd | Construction | 2019 |
| N L C Nova Lift Co. Limited | Administrative & support | 1997 |
| N.K Engineering Ltd | Construction | 2007 |
| Nails to Wood Carpentry Ltd | Manufacturing | 2020 |
| Namiko Swimming School LLP | | 2023 |
| Natalie Plastic and More Ltd | Wholesale & retail | 2025 |
| Nationcare Construction Limited | Construction | 2019 |
| Natural Barrier Co Ltd | Manufacturing | 2024 |
| Naylor Enterprises Limited | Real estate | 2023 |
| Naylor Properties Limited | Real estate | 2015 |
| NCH Consulting Limited | Professional & scientific | 2018 |
| NCS Employee Ownership Trustee Limited | Extraterritorial | 2023 |
| NCS Technology Limited | Construction | 1998 |
| Nebuchadnezzar 2011 Limited | Administrative & support | 2011 |
| Nepicar Groundcare Limited | Agriculture & fishing | 2010 |
| Nerakk Property Solutions Ltd | Real estate | 2024 |
| Networld Consultants Limited | Information & communication | 2014 |
| New Success Kent Limited | Wholesale & retail | 2013 |
| Next Level Electrical Ltd | Construction | 2025 |
| Nextlevel Mentoring Ltd | Professional & scientific | 2011 |
| Nexus Drinks Systems Limited | Wholesale & retail | 2021 |
| Night Bear Ltd | Wholesale & retail | 2025 |
| Ninenineteen Ltd | Information & communication | 2025 |
| NJM Groundworks Limited | Administrative & support | 2023 |
| NJP Advisory Ltd | Professional & scientific | 2026 |
| NJR Group Holdings Limited | Financial services | 2026 |
| Noctua Solutions Ltd | Professional & scientific | 2014 |
| Nollgold Carpets Ltd | Wholesale & retail | 2024 |
| Noonsec Ltd | Information & communication | 2025 |
| Norman Allen Group Travel Limited | Administrative & support | 1992 |
| Norman Forestry Limited | Administrative & support | 2015 |
| Norrvik UK Limited | Wholesale & retail | 2025 |
| North & South Group Limited | Financial services | 2023 |
| Notjustboxing Limited | Professional & scientific | 2024 |
| Nova Lift Co. Ltd | Professional & scientific | 2011 |
| Novas High Technology Ltd | Manufacturing | 2018 |
| Nu-Venture Coaches Limited | Transport & logistics | 1976 |
| Numquam Cede Limited | Administrative & support | 2015 |
| Nursery Task Ltd | Wholesale & retail | 2024 |
| OA Marketing Ltd | Professional & scientific | 2024 |
| Oak Drive 1958 Limited | Extraterritorial | 2014 |
| Oakhurst Commerce Limited | Administrative & support | 2016 |
| Oakleigh Roofing (Kent) Ltd | Construction | 2025 |
| OB Media Consultants Ltd | Information & communication | 2012 |
| Obsidian Fire and Security Limited | Administrative & support | 2015 |
| Obsidian Racing Limited | Wholesale & retail | 2023 |
| Obsidian Security Limited | Construction | 2003 |
| Ocean Harvest Technology (UK) Limited | Wholesale & retail | 2018 |
| Oceanic Systems (UK) Ltd | Manufacturing | 2016 |
| OCR Cargo Services Ltd | Transport & logistics | 2012 |
| Odysseium Ltd | Information & communication | 2023 |
| OET Consulting Ltd | Information & communication | 2025 |
| Office Innovations Ltd | Administrative & support | 2016 |
| Offset Print & Packaging Limited | Manufacturing | 1984 |
| Offset Print Limited | Professional & scientific | 2015 |
| One Construct Carpentry Ltd | Manufacturing | 2024 |
| Onis Pizza Ltd | Wholesale & retail | 2025 |
| OP Automotive LLP | | 2020 |
| Optimal Quality Solutions Ltd | Professional & scientific | 2026 |
| Optimum Appointments Ltd | Administrative & support | 2009 |
| Optimum Grace Ltd | Real estate | 2025 |