| Murphy Holdco Ltd | Real estate | 2021 |
| Muse Cleaning Services Ltd | Administrative & support | 2015 |
| Music Beyond the Lines Ltd | Education | 2023 |
| Mutuo Solutions Limited | Financial services | 2024 |
| Muvi Ltd | Real estate | 2022 |
| My Greengrocer Ltd | Wholesale & retail | 2021 |
| My PA Limited | Extraterritorial | 2008 |
| MZ Holding Group Ltd | Financial services | 2025 |
| N H Welham Investments Ltd | Real estate | 2022 |
| N Reeves Consulting Ltd | Professional & scientific | 2025 |
| N. Garcia Crime Prevention Consultancy Ltd | Professional & scientific | 2018 |
| N.C. Wall Services Ltd | Other services | 2025 |
| NA Connell Limited | Professional & scientific | 2019 |
| Nadathur Family Office UK Ltd | Professional & scientific | 2023 |
| Nadathur UK Limited | Administrative & support | 2017 |
| Naivis Ltd | Hospitality | 2018 |
| Natalie Jane Ltd | Administrative & support | 2002 |
| Natalie Reid Marketing Ltd | Professional & scientific | 2024 |
| Naycħ Collective Ltd | Wholesale & retail | 2025 |
| NCE London Ltd | Manufacturing | 2005 |
| Neatblend Properties Limited | Real estate | 1989 |
| Neds Motors Limited | Wholesale & retail | 2010 |
| Needham Lawrence Services Limited | Professional & scientific | 2016 |
| Needit UK Limited | Wholesale & retail | 2025 |
| Neev London Limited | Wholesale & retail | 2020 |
| Nest of Treasures Ltd | Administrative & support | 2011 |
| Netwrk Ltd | Administrative & support | 2016 |
| Neuwell Limited | Wholesale & retail | 2017 |
| New ERA Scaffolding Ltd | Construction | 2012 |
| Newman Heating Limited | Construction | 2005 |
| Newstead House Limited | Households | 1986 |
| Next Build CT Ltd | Construction | 2025 |
| Nextgen Lettings Ltd | Real estate | 2021 |
| Nextgen Lettings Portsmouth Ltd | Real estate | 2024 |
| Nextgen Lettings Swindon Ltd | Real estate | 2024 |
| Nextgen Web Solutions PVT Ltd | Information & communication | 2007 |
| Nexus Paper Solutions Limited | Wholesale & retail | 2002 |
| NF Dent Hygiene Ltd | Health & social care | 2024 |
| NH Construction Law Consultants Limited | Professional & scientific | 2020 |
| Nicaro Consulting Limited | Professional & scientific | 2014 |
| Nicholson Glover Associates Limited | Administrative & support | 2017 |
| Nicholson Road Freehold Limited | Households | 2023 |
| Nightingale Holistic Services Limited | Health & social care | 2009 |
| NIK Hannah Limited | Manufacturing | 2014 |
| Ninehams Court Residents Association Limited | Households | 1964 |
| Nineteen Seventy Seven Limited | Other services | 2023 |
| Ninja Media Ltd | Professional & scientific | 2017 |
| Nintoo Inc Ltd | Wholesale & retail | 2025 |
| Nisus Consulting Limited | Professional & scientific | 2015 |
| NJ Consult Ltd | Professional & scientific | 2024 |
| NJI Developments Ltd | Real estate | 2015 |
| NJK Health Ltd | Health & social care | 2025 |
| Noahone SPV Ltd | Real estate | 2023 |
| Noctra AI Ltd | Professional & scientific | 2026 |
| Nolan Building & Consultancy Limited | Construction | 2018 |
| Noop London Ltd | Wholesale & retail | 2017 |
| Norman Lewis Business Equipment Limited | Wholesale & retail | 1984 |
| Normans of London Ltd | Transport & logistics | 2019 |
| North Atlantic (Crewing) Limited | Agriculture & fishing | 1990 |
| North Atlantic (Holdings) Limited | Agriculture & fishing | 1993 |
| North Atlantic Fishing Company Limited | Agriculture & fishing | 1922 |
| North Atlantic Seafoods Limited | Agriculture & fishing | 1962 |
| North Downs Estates Limited | Construction | 2018 |
| Northflow Limited | Information & communication | 1984 |
| Northwest 6 Ltd | Real estate | 2016 |
| Northwold Electrical Services LLP | | 2017 |
| Novon Group Ltd | Construction | 2020 |
| Novum Office Limited | Real estate | 2017 |
| Nowdotti Ltd | Information & communication | 2019 |
| NST Energy Investments Limited | Real estate | 2026 |
| Nurturing Independence and Empowering Lives (Niel) Children Support Services Limited | Health & social care | 2023 |
| Nutfield Homes Limited | Construction | 2004 |
| Nutshell Technology Ltd | Information & communication | 2016 |
| Nuvola Analytics Ltd | Information & communication | 2017 |
| NWL Property Ltd | Real estate | 2013 |
| O'Gormantaylor Limited | Administrative & support | 2006 |
| O. & M. Office Equipment Limited | Wholesale & retail | 1958 |
| O. H. C. Caterham Ltd | Hospitality | 2023 |
| Oak Projects Ltd | Professional & scientific | 2018 |
| Oakbury Ltd | Professional & scientific | 2007 |
| Oakfield Lodge Property Ltd | Real estate | 2020 |
| Oakgrove Holdings Ltd | Construction | 2024 |
| Oakgrove Winchester 1 Ltd | Construction | 2026 |
| Oakhill Carpentry Ltd | Manufacturing | 2023 |
| Oakland Industrial Ltd | Wholesale & retail | 2020 |
| Oakpines Warlingham Limited | Households | 2022 |
| Oases Success Ltd | Administrative & support | 2025 |
| OB1 Building Services Limited | Construction | 2018 |
| OCB Construction Limited | Construction | 2011 |
| OCB Homes Limited | Construction | 2013 |
| OCB Limited | Construction | 2008 |
| Octogra Limited | Professional & scientific | 2020 |
| Old Caterhamians Sports Club Limited | Arts & recreation | 2024 |
| Oliver General Builders Limited | Construction | 2011 |
| Oliver Stock Limited | Real estate | 2024 |
| Olly & Belle Ltd | Wholesale & retail | 2010 |
| OM SRI SAI Properties Ltd | Real estate | 2019 |
| Omega Wills Limited | Professional & scientific | 2004 |
| Omenatic Limited | Mining & quarrying | 2023 |
| ON the Groundworks Limited | Construction | 2017 |