| Njmb Associates Ltd | Professional & scientific | 2017 |
| NJR Group Limited | Professional & scientific | 2019 |
| NLS Beauty Ltd | Other services | 2016 |
| Nncbuilders Ltd | Real estate | 2025 |
| NO Fakie Ltd | Information & communication | 2017 |
| NO Sweet Lies Ltd | Health & social care | 2026 |
| Noah’S Grill Ltd | Hospitality | 2024 |
| Noble Finance Services Limited | Real estate | 2017 |
| Noble Funeral Service Limited | Other services | 2009 |
| Noji Maranatha Limited | Wholesale & retail | 2015 |
| Nolli Ltd | Information & communication | 2026 |
| Nomad Workhouse Limited | Professional & scientific | 2013 |
| Noors Halal Butcher Ltd | Wholesale & retail | 2026 |
| Nordein Ltd | Professional & scientific | 2019 |
| Nordic Chemical Solutions UK Ltd | Manufacturing | 2015 |
| North Camp PIT Stop Ltd | Wholesale & retail | 2024 |
| North Hill Advisory Partners Limited | Financial services | 2016 |
| Northfield Engineering Limited | Construction | 1998 |
| Northolt Assets Future Limited | Wholesale & retail | 2010 |
| Northpop Limited | Hospitality | 2025 |
| Northstar Commercial Ltd | Professional & scientific | 2026 |
| Northstar Consultancy Services Ltd | Administrative & support | 2025 |
| Northwood Inventory Management Ltd | Households | 2019 |
| NOT a Duff Word Ltd | Professional & scientific | 2017 |
| Nova 017 Ltd | Information & communication | 2017 |
| Novascapes Design & Build Ltd | Administrative & support | 2020 |
| NPP Installations Ltd | Construction | 2021 |
| Nrcr Limited | Construction | 2024 |
| Nrna UK Ltd | Health & social care | 2023 |
| Numbers Management Limited | Professional & scientific | 2011 |
| Nusard Limited | Households | 1977 |
| NV Trade Services Ltd | Construction | 2026 |
| NYAMECARE4U Limited | Health & social care | 2024 |
| Nybor Systems Limited | | 1973 |
| O'Malley Home and Gift Ltd | Wholesale & retail | 2022 |
| O'Neill Limited | Administrative & support | 2017 |
| O'Neill London Ltd | Information & communication | 2014 |
| Oak and Cedar Limited | Administrative & support | 2026 |
| Oak Apples Drive Management Company Limited | Households | 2019 |
| Oak Block Management Ltd | Households | 2022 |
| Oak Court (Farnham) Limited | Households | 2003 |
| Oak Tree Guesthouse Limited | Hospitality | 2025 |
| Oakfield Place (Fleet Road) Management Company Limited | Professional & scientific | 2003 |
| Oakland Water Services Ltd | Water & waste | 2024 |
| Oaklea Carers Ltd | Public administration | 2025 |
| Oakridge (Bridgeman Drive) Limited | Real estate | 2017 |
| Oakridge Developments UK Limited | Construction | 2010 |
| Oakwood Financial Services Ltd | Financial services | 2014 |
| Oakwood Gardens Limited | Administrative & support | 2016 |
| Oasis Trading Impex Limited | Wholesale & retail | 2010 |
| Oastdean Limited | Hospitality | 1987 |
| OC3 Ltd | Wholesale & retail | 2025 |
| OC317185 LLP | | 2006 |
| Ochre Square Mechanical Services Ltd | Construction | 2021 |
| ODS Electrical Services Limited | Construction | 2008 |
| OJD Solutions Limited | Information & communication | 2014 |
| Okabe Leisure Limited | Agriculture & fishing | 2020 |
| OLI Turkish Barber Limited | Other services | 2021 |
| OM SRI SAI Superstores Limited | Wholesale & retail | 2025 |
| Omar Transportation Ltd | Transport & logistics | 2023 |
| Omega Development Ltd | Information & communication | 2010 |
| Omelif Limited | Hospitality | 2019 |
| Omniappnet Ltd | Information & communication | 2025 |
| On-Ground Logistics Ltd | Transport & logistics | 2026 |
| Onami Systems Limited | Information & communication | 2005 |
| Once Milano Ltd | Wholesale & retail | 2011 |
| One Beyond Limited | Information & communication | 2000 |
| One Life Health Support Ltd | Administrative & support | 2021 |
| One Planet Properties Ltd | Extraterritorial | 2009 |
| One Site Global Holdings Limited | Information & communication | 2024 |
| One Site Global Limited | Information & communication | 2019 |
| One Spear Films Ltd | Information & communication | 2016 |
| One to One Photography Ltd | Professional & scientific | 2015 |
| Oneb Technologies Ltd | Information & communication | 2016 |
| Onformconsulting Ltd | Wholesale & retail | 2019 |
| Online Havon Ltd | Wholesale & retail | 2023 |
| Online Hits Ltd | Information & communication | 2023 |
| Oodles Farnborough Limited | Hospitality | 2025 |
| Open Road Motorcycles Ltd | Wholesale & retail | 2015 |
| Opexbutterfly Ltd | Professional & scientific | 2024 |
| Opsyte Online Ltd | Information & communication | 2019 |
| Optikos Hub Limited | Information & communication | 2017 |
| Optimus PRIME86 Ltd | Transport & logistics | 2021 |
| Options Facilities Management Ltd | Administrative & support | 2006 |
| Optipharm Solutions Limited | Health & social care | 2025 |
| Opus Interior Projects Limited | Construction | 2010 |
| Orba Group Ltd | Wholesale & retail | 2019 |
| Orchid Recruitment Ltd | Administrative & support | 2026 |
| Orchir Spa Limited | Other services | 2026 |
| Orchis London Limited | Construction | 2025 |
| Oregano Farnborough Limited | Wholesale & retail | 2025 |
| Origen Financial Services Limited | Administrative & support | 2000 |
| Origen Limited | Administrative & support | 2004 |
| Origen Trustee Services Limited | Professional & scientific | 1985 |
| Origin Bidco Limited | Administrative & support | 2020 |
| Origin Co EUR Limited | Financial services | 2023 |
| Origin Co USD Limited | Financial services | 2023 |
| Origin Midco Limited | Administrative & support | 2020 |
| Original Sash Ltd | Extraterritorial | 2011 |
| Orriss Limited | Real estate | 2019 |