| Nightingales Residents Association Limited | Households | 1989 |
| Nigori Ltd | Hospitality | 2019 |
| Nikaia Consulting Limited | Professional & scientific | 2020 |
| Niko's Cleaning Ltd | Administrative & support | 2021 |
| Nimble Tech Systems Limited | Wholesale & retail | 2023 |
| Nine DOT Insights Limited | Professional & scientific | 2018 |
| Nine Mile Limited | Agriculture & fishing | 2017 |
| Ninety Thousand Hours Ltd | Administrative & support | 2007 |
| Nineveh 1 Limited | Financial services | 2019 |
| Nineveh 2 Limited | Financial services | 2019 |
| Nipper Kits & Components Limited | Wholesale & retail | 1971 |
| Niriella Estates Limited | Real estate | 1997 |
| Niton UK Limited | Professional & scientific | 2000 |
| NM Limited | Construction | 1999 |
| NO. 26 ERP Consulting Limited | Information & communication | 2023 |
| Noble Hair Company Ltd | Other services | 2013 |
| Nobre Studio Ltd | Wholesale & retail | 2024 |
| Nofakefriends Ltd | Wholesale & retail | 2020 |
| Noisy Little Productions Ltd | Arts & recreation | 2018 |
| Nomad Acoustics Ltd | Extraterritorial | 2015 |
| Noomi Ltd | Wholesale & retail | 2025 |
| Noon Healthcare Solutions Ltd | Health & social care | 2022 |
| Noor Specialist Homes Ltd | Hospitality | 2025 |
| Noot Limited | Information & communication | 2012 |
| Norbert Hars Building Ltd | Construction | 2020 |
| Norman Court Montessori Community Interest Company | Education | 2013 |
| North Dorset Storage Ltd | Real estate | 2021 |
| North Dorset Workshops Limited | Real estate | 2017 |
| North Dredging Ltd | Construction | 1997 |
| North Equipment Ltd | Administrative & support | 2014 |
| North South Pubs Ltd | Hospitality | 2023 |
| North Walls Enterprises Ltd | Wholesale & retail | 2024 |
| Northamtec Investments & Holdings Limited | Financial services | 2014 |
| Northants Builders and Interiors Ltd | Construction | 2022 |
| Northbrook Arms Ltd | Hospitality | 2019 |
| Northbrook Bower (Bishops Waltham) RTM Company Limited | Households | 2011 |
| Northbrook House Limited | Households | 2002 |
| Northbrook Management (Bishop's Waltham) Limited | Households | 2002 |
| Northbrook Vineyard Limited | Agriculture & fishing | 2018 |
| Northern South Engineering Ltd | Manufacturing | 2026 |
| Northern South Ltd | Professional & scientific | 2025 |
| Northfields Twyford Limited | Administrative & support | 2011 |
| Northgate Lodge Freehold Limited | Households | 2025 |
| Northgate Lodge Management Company Limited | Households | 2011 |
| Northlands House (Management) Limited | Households | 1984 |
| Norton Chase Management Company Limited | Households | 2022 |
| Nostra Italia Ltd | Wholesale & retail | 2024 |
| Notion Health Ltd | Health & social care | 2025 |
| Notion Property Investments Ltd | Real estate | 2020 |
| Notion Residential Properties LLP | | 2021 |
| Notion Services Ltd | Construction | 2014 |
| Nouveau Architecture Ltd | Professional & scientific | 2010 |
| Nova-Scotia Estates | Professional & scientific | 1956 |
| Novare Renovations & Build Ltd | Construction | 2024 |
| Novatia PLC | Information & communication | 2003 |
| Novatia Services Limited | Information & communication | 2011 |
| Novatrix Operations Ltd | Professional & scientific | 2026 |
| Novetica Limited | Professional & scientific | 2025 |
| Novo Meddev Ra/Qa Consultancy Limited | Professional & scientific | 2022 |
| Noxpoint Geospatial Ltd | Professional & scientific | 2026 |
| NRS Building Ltd | Construction | 2023 |
| NSD Studio Ltd | Professional & scientific | 2022 |
| NSM Foods Limited | Hospitality | 2021 |
| Nuclear Maritime Limited | Professional & scientific | 2023 |
| Nugent Investments Ltd | Financial services | 2023 |
| Nuneaton Investment Company Limited | Real estate | 1957 |
| Nurokor Lifetech Limited | Health & social care | 2020 |
| Nursing Homes Services Limited | Health & social care | 1990 |
| Nutbourne Management (Southern) Ltd | Households | 2018 |
| Nutcombe Hill Ltd | Administrative & support | 2013 |
| Nutri-Research Consulting Ltd | Professional & scientific | 2025 |
| NUVOLA9 Recruitment Ltd | Administrative & support | 2024 |
| NWP Spectrum Holdings Limited | Professional & scientific | 2002 |
| O'Hara Services 1 Ltd | Health & social care | 2022 |
| O'Hara Services 2 Ltd | Health & social care | 2022 |
| O.W.E Properties Ltd | Real estate | 2024 |
| Oaka Consulting Limited | Professional & scientific | 2023 |
| Oakdene (Fair Oak) Property Management Co. Ltd. | Households | 1990 |
| Oakheart Fleet Management Limited | Manufacturing | 2022 |
| Oakhill Properties (Leicester) Limited | Real estate | 1950 |
| Oakleaf Investment Holdings Ltd | Financial services | 2021 |
| Oakleigh Court (Bognor Regis) Limited | Households | 1973 |
| Oakley Wright Ltd | Administrative & support | 2022 |
| Oakmount Property Estate Limited | Real estate | 2026 |
| Oakridge Property Services Group Ltd | Construction | 2025 |
| Oakwood (Midhurst) Management Company Limited | Households | 1987 |
| OB Architecture Ltd | Professional & scientific | 2010 |
| OBA Holdings Limited | Financial services | 2018 |
| Obsessive AF Ltd | Professional & scientific | 2019 |
| Obvio Financial Planning Limited | Professional & scientific | 2024 |
| OC & Sons Roofing and Guttering Ltd | Construction | 2025 |
| Occlude (UK) Limited | Health & social care | 2013 |
| Occupational Safety and Health Consultancy Services Limited | Administrative & support | 2011 |
| Ocean House East Wittering Ltd | Households | 2021 |
| Ocean Nails Winchester Limited | Other services | 2024 |
| Ocean Venture Limited | Real estate | 2001 |
| Oceanic Engineering Consultants Ltd | Administrative & support | 2013 |
| Oculus Prime Homes Limited | Real estate | 2020 |
| OFF Grid Installs Limited | Construction | 2022 |
| OFF Piste Marine Limited | Manufacturing | 2022 |