| NO 1 Thames Street Limited | Households | 2000 |
| NO Fuss Security Ltd | Information & communication | 2022 |
| No-Limit Property Services Ltd | Construction | 2025 |
| NO. 1 George Street Limited | Wholesale & retail | 2018 |
| NO. 1 Reclaims Limited | Wholesale & retail | 2019 |
| Nolla Handchain Jewellery Limited | Manufacturing | 2025 |
| Nomadic Expeditions Limited | Administrative & support | 1997 |
| NON World UK Limited | Wholesale & retail | 2025 |
| Noracare Limited | Public administration | 2025 |
| Norfolk Health & Wellness Ltd | Professional & scientific | 2024 |
| North Avenue Guest House Ltd | Hospitality | 2024 |
| North Court (the Ridges) Freehold Company Limited | Households | 2008 |
| North Lodge Owners Limited | Households | 2015 |
| North Shore Investments Ltd | Financial services | 2024 |
| North Star Investments and Holdings Ltd | Financial services | 2023 |
| Northland Court Limited | Real estate | 2001 |
| Northwood (Wokingham) Ltd | Real estate | 2003 |
| Norton Air Conditioning Ltd | Construction | 2015 |
| Nosey UK Ltd | Manufacturing | 2024 |
| Notties Trading Limited | Wholesale & retail | 2016 |
| Nourish & Flow Limited | Other services | 2017 |
| Nova MCC Ltd | Professional & scientific | 2023 |
| Novalink Software Ltd | Information & communication | 2025 |
| Novalis Consulting LLP | | 2025 |
| Novamex Associates Limited | Professional & scientific | 2016 |
| Novasoft Tech. LLP | | 2026 |
| Novelchange Limited | Information & communication | 1996 |
| Novelty Bits and Bobs Ltd | Wholesale & retail | 2022 |
| Novius Industries (UK) Limited | Wholesale & retail | 2025 |
| Novo Fusion Limited | Wholesale & retail | 2024 |
| NOW Flooring Ltd | Construction | 2010 |
| Nowroozi Consulting Limited | Information & communication | 2025 |
| NPK Consultant Services Ltd | Professional & scientific | 2012 |
| NR Professional Business Solutions Ltd | Administrative & support | 2026 |
| NS Beverages Ltd | Wholesale & retail | 2024 |
| NS MRM Ltd | Wholesale & retail | 2025 |
| NS3 UK Limited | Education | 2001 |
| NSH Finance Limited | Professional & scientific | 2017 |
| Nsmv Limited | Real estate | 2025 |
| Nspiration Group Limited | Professional & scientific | 2021 |
| Nspiration Limited | Professional & scientific | 2018 |
| Nspiration Property Limited | Real estate | 2020 |
| NSV Limited | Health & social care | 2015 |
| Nuaki Limited | Information & communication | 2025 |
| Nugee Court (Management) Company Ltd. | Households | 1979 |
| Nuglio Ltd | Information & communication | 2025 |
| Numbers 1 to 4 Barkham Manor Limited | Real estate | 1992 |
| Nurova Equine Ltd | Other services | 2025 |
| Nurserypath Ltd | Administrative & support | 2026 |
| Nuru Clinic Limited | Health & social care | 2025 |
| Nutbourne Holdings Limited | Real estate | 2025 |
| Nutrition Nourishment Ltd | Professional & scientific | 2020 |
| NV Advisory Limited | Professional & scientific | 2025 |
| Nxgi Technologies Ltd | Information & communication | 2025 |
| O&C Consulting Limited | Professional & scientific | 2010 |
| O'Rourke Personnel Limited | Administrative & support | 2011 |
| O.E.S Pulford Ltd | Real estate | 2021 |
| Oak & PLY Ltd | Wholesale & retail | 2026 |
| Oak Medical Science Ltd | Professional & scientific | 2019 |
| Oak Tree Residents Association Limited | Households | 1983 |
| Oakford Associates Ltd | Other services | 2019 |
| Oakhill Advisory Limited | Extraterritorial | 2024 |
| Oakhurst Close Management Company Limited | Households | 2010 |
| Oaklands IT Ltd | Information & communication | 2025 |
| Oakley Food Projects Design LLP | | 2023 |
| Oakley Food Projects Ltd | Construction | 2012 |
| Oakmead Marketing Group Ltd. | Professional & scientific | 2016 |
| Oaksmere Residents Association Limited | Households | 1981 |
| Oaktree Interiors Limited | Construction | 1992 |
| Oakwood Youth Challenge | Arts & recreation | 2002 |
| Obbligato Limited | Information & communication | 1994 |
| Ocean Property Investments LLP | | 2005 |
| Ochre Box Ltd | Wholesale & retail | 2022 |
| Octavia Corporate Interiors Limited | Professional & scientific | 2024 |
| ODD Inch Limited | Information & communication | 2021 |
| ODE to the Motherland Ltd | Wholesale & retail | 2023 |
| Odedra Brothers Limited | Wholesale & retail | 1983 |
| Odyssey E-Commerce Ltd. | Wholesale & retail | 2022 |
| OFF and on Ltd | Information & communication | 2025 |
| OFF the Wall Vans Limited | Manufacturing | 2025 |
| OG Car Sales Ltd | Wholesale & retail | 2023 |
| Ohana Limited | Hospitality | 2009 |
| OHR Collective Ltd | Professional & scientific | 2023 |
| OIL & GAS Processing Consultancy Limited | Professional & scientific | 2025 |
| Oilbs Limited | Manufacturing | 2015 |
| OIS Consulting Limited | Professional & scientific | 2008 |
| Ojasvi Consultancy Limited | Information & communication | 2026 |
| OJL Mortgages Ltd | Financial services | 2017 |
| Oktovia Limited | Information & communication | 2023 |
| OL Psychotherapy and Consulting Ltd | Professional & scientific | 2025 |
| Old Kennels Court Limited | Households | 1962 |
| Old Stable Way Management Company Limited | Households | 2024 |
| Old Tollgate Management Company Limited | Professional & scientific | 2013 |
| Olimatt Limited | Information & communication | 2025 |
| Olinnovation Limited | Professional & scientific | 2024 |
| Olive Branch Wellbeing Ltd | Health & social care | 2023 |
| Olivia Court Management Company Limited | Households | 1978 |
| Oliviella Ltd | Wholesale & retail | 2021 |
| Olsons Group Ltd | Wholesale & retail | 2019 |
| OM Assets Ltd | Real estate | 2017 |