| National Physical Laboratory Limited | Professional & scientific | 1994 |
| Natural View Products Limited | Wholesale & retail | 2020 |
| NC Property Developments Limited | Construction | 2015 |
| Negotiation Whisperer Ltd | Professional & scientific | 2025 |
| Nelson Scott Recruitment Services Ltd | Administrative & support | 2011 |
| Neokosmos Limited | Information & communication | 2026 |
| Neovita Ltd | Manufacturing | 2022 |
| Nereid Consultancy Limited | Professional & scientific | 2019 |
| Nesca Food Limited | Manufacturing | 2019 |
| Nest and Vine Peckham Limited | Wholesale & retail | 2026 |
| Nestonomy Ltd | Real estate | 2025 |
| Netfoxx Ltd | Information & communication | 2022 |
| Network 3 Communications Limited | Information & communication | 2005 |
| Networld Solutions Ltd | Information & communication | 2010 |
| Never Matched Ltd | Wholesale & retail | 2021 |
| New Haweli Teddington Limited | Hospitality | 2019 |
| Newham Park Holdings Ltd | Professional & scientific | 2021 |
| Newhart Adjusters Limited | Administrative & support | 1999 |
| Newhart Associates Limited | Administrative & support | 1995 |
| Newmanstrikingfit Ltd | Education | 2023 |
| Next Level Resell Ltd | Professional & scientific | 2022 |
| Nextphase Strategy Ltd | Professional & scientific | 2026 |
| Ngpdt Electric Europe Ltd | Wholesale & retail | 2013 |
| NHB Bookkeeping Services Limited | Professional & scientific | 2013 |
| NIC Peters Ltd | Professional & scientific | 2026 |
| Nick Keene Limited | Administrative & support | 2007 |
| Nidrekol Limited | Health & social care | 2014 |
| Niki Mauthner Design Limited | Professional & scientific | 2016 |
| Nikki Williams Interiors Ltd | Wholesale & retail | 2025 |
| Nitro Change Management Ltd | Professional & scientific | 2016 |
| Nnnb Ltd | Hospitality | 2016 |
| NO Agent Ltd | Extraterritorial | 2017 |
| Noodleshot Ltd | Information & communication | 2020 |
| Norman Glamorgan Limited | Households | 1993 |
| Normandy Court Development Limited | Real estate | 2016 |
| Normansfield Ltd | Households | 2023 |
| North Barry Ltd | Real estate | 2021 |
| North Court (Twickenham) Ltd | Households | 2011 |
| North Track Solutions Ltd | Information & communication | 2024 |
| Northumberland House Management Limited | Households | 2007 |
| Northwest Asset Holdings Ltd | Real estate | 2026 |
| Northwood Advisory Limited | Professional & scientific | 2023 |
| Norwood Green(Block C)Management Company Limited | Households | 1985 |
| Nova Fluid Mechanics Ltd | Professional & scientific | 2019 |
| Nova Star Consultancy Ltd | Real estate | 2023 |
| Nova Techset Ltd | Administrative & support | 1989 |
| Novative Services Ltd | Information & communication | 2021 |
| Novo Plastering Services Limited | Construction | 2024 |
| Novo Shipping Limited | Transport & logistics | 2016 |
| Noyos PS Limited | Construction | 2026 |
| NPL Laboratories Limited | Professional & scientific | 1994 |
| NPL Management Limited | Other services | 1994 |
| Nplsc Catering Ltd | Hospitality | 2018 |
| NPR Properties Limited | Real estate | 2020 |
| NRG Management Consultancy Limited | Professional & scientific | 2016 |
| Nrvision Ltd | Wholesale & retail | 2025 |
| NS Manufacturing Ltd | Professional & scientific | 2025 |
| NT Landscape and Garden Care Ltd | Professional & scientific | 2026 |
| NU Kumar Ltd | Health & social care | 2013 |
| Nullo Design Ltd | Wholesale & retail | 2020 |
| Number 10 Princes Road Limited | Hospitality | 2011 |
| Number One Feltham LLP | | 2018 |
| NUT Case Luggage Limited | Wholesale & retail | 2019 |
| Nuvira London Cleaning Ltd | Administrative & support | 2026 |
| NVS Business Global Ltd | Manufacturing | 2011 |
| NYA Enterprises Ltd | Wholesale & retail | 2020 |
| O&L 1942 Limited | Real estate | 2018 |
| O'Brien (WT) Consultancy Ltd | Professional & scientific | 2022 |
| O-Video Limited | Wholesale & retail | 1998 |
| Oakacre Developments Limited | Construction | 2011 |
| Oasis Watering Services Ltd | Administrative & support | 2024 |
| OB Moves Limited | Transport & logistics | 2010 |
| Ocdata Limited | Professional & scientific | 2014 |
| Ocean Logistics Limited | Transport & logistics | 1994 |
| Oceana Drycleaners Ltd | Professional & scientific | 2015 |
| Ocult Jewellery Limited | Manufacturing | 2025 |
| ODD Socks Consultancy Limited | Health & social care | 2015 |
| Oddacre Limited | Households | 1999 |
| Offpaper Ltd | Administrative & support | 2018 |
| OKR PR Limited | Professional & scientific | 2025 |
| Old Bridge Street Limited | Financial services | 2005 |
| Old Hamptonians' Sports Ground Limited | Arts & recreation | 1931 |
| Old Nursery Way Limited | Administrative & support | 2005 |
| Old Vicarage(Kingston Road)Management Company Limited(The) | Households | 1985 |
| Oletti Services Ltd | Real estate | 2023 |
| Oliver Upton Limited | Professional & scientific | 2006 |
| Oliviahill UK Limited | Real estate | 2008 |
| Olos Construction Limited | Construction | 2026 |
| Ommanney 8 Consulting Limited | Professional & scientific | 2018 |
| Omnihost Ltd | Information & communication | 2021 |
| Omniproject Limited | Information & communication | 2011 |
| ON a Plane Again Ltd | Information & communication | 2025 |
| ON Pointe Limited | Wholesale & retail | 2005 |
| Onelovehealth Ltd | Health & social care | 2021 |
| Onepet UK Ltd | Financial services | 2020 |
| Oneplan Health UK Ltd | Financial services | 2020 |
| Ones and Zeros Ltd | Professional & scientific | 2014 |
| Ontapp Ltd | Information & communication | 2020 |
| Oodlesof Ltd | Wholesale & retail | 2025 |
| Opiner Limited | Information & communication | 2019 |