| NM Fire Consulting & Property Management Limited | Public administration | 2026 |
| NMK Cladding Ltd | Construction | 2015 |
| NMP Construction Limited | Construction | 2020 |
| NO 46 Limited | Real estate | 2017 |
| NO Nonsense Plumbing Ltd | Construction | 2022 |
| NO Spoon Capital Limited | Education | 2025 |
| Noakes Management Limited | Households | 2002 |
| Noborder Electrical Services Ltd | Other services | 2012 |
| Noch Ltd | Administrative & support | 2019 |
| NON Stop Fashion Limited | Wholesale & retail | 2016 |
| Nonna Rosa Limited | Other services | 2012 |
| Noodels XIE Games Ltd | Information & communication | 2025 |
| Noodle Studio Ltd | Professional & scientific | 2018 |
| Norberto Ltd | Transport & logistics | 2016 |
| Norbury Mail Ltd | Transport & logistics | 2024 |
| Norden Property Management Limited | Real estate | 2021 |
| Nordens Audit Limited | Professional & scientific | 2020 |
| Nordens Cloud and Advisory Limited | Professional & scientific | 2005 |
| Nordens Farringdon Limited | Professional & scientific | 2020 |
| Nordens Limited | Professional & scientific | 2003 |
| Nordens Property Partnership Limited | Real estate | 2025 |
| Nordens Wealth Management Limited | Financial services | 2025 |
| Norlington Holdings Limited | Financial services | 2021 |
| Northants Cars Limited | Administrative & support | 2024 |
| Northbrooke UK Limited | Real estate | 2010 |
| Northern Freehold Ltd | Real estate | 2017 |
| Northfield Haulage Limited | Transport & logistics | 2022 |
| Northlight Architects Limited | Professional & scientific | 2023 |
| Norton Construction Ltd | Construction | 2025 |
| Nosamac Care Services Ltd | Health & social care | 2010 |
| Nova Giveaways Limited | Arts & recreation | 2025 |
| Novafreen Prime Ltd | Wholesale & retail | 2026 |
| Novavista Limited | Professional & scientific | 2007 |
| Nowvit Limited | Wholesale & retail | 2025 |
| NPA Consulting Limited | Professional & scientific | 2015 |
| Npsych Clinical Neurosciences Ltd | Health & social care | 2012 |
| NRG Fireprotection Ltd | Construction | 2018 |
| NRI Property Solutions Ltd | Real estate | 2021 |
| NRK 88 Ltd | Hospitality | 2020 |
| Ntier Limited | Financial services | 1999 |
| Ntrz Limited | Wholesale & retail | 2026 |
| Nuage Network Limited | Construction | 2015 |
| Nuearth Limited | Construction | 2021 |
| Numa Private Concierge Ltd | Administrative & support | 2026 |
| Number 1671 Ltd | Arts & recreation | 2016 |
| Nunu Financial Solutions Ltd | Extraterritorial | 2014 |
| Nurest Ltd | Wholesale & retail | 2026 |
| Nuroshift Ltd | Information & communication | 2025 |
| Nurture IT Limited | Information & communication | 2006 |
| Nutcase Nuts Limited | Manufacturing | 2022 |
| Nutla Ltd | Hospitality | 2012 |
| Nutmeg Editing Limited | Other services | 2016 |
| Nutra Secret Ltd | Arts & recreation | 2024 |
| Nutrient Soul Ltd | Wholesale & retail | 2023 |
| Nutrients ABC Ltd | Real estate | 2019 |
| NUTRITION4HEALTH Ltd | Health & social care | 2024 |
| NUY Consultancy Ltd | Health & social care | 2012 |
| NV Collections UK LP | | 2019 |
| NVA Video Analytics Limited | Information & communication | 2022 |
| NXS Hair (UK) Ltd | Wholesale & retail | 2011 |
| Nyota Retreats Ltd | Real estate | 2025 |
| O'Donnell Enterprises Limited | Information & communication | 2023 |
| O'Keefe Medical Ltd | Health & social care | 2014 |
| O'Neill Structural Services Ltd | Administrative & support | 2019 |
| O2 Spa Limited | Health & social care | 2025 |
| Oak House (Ashford) Limited | Households | 2008 |
| Oakfield Spring Limited | Real estate | 2016 |
| Oakington Court Freeholders Ltd | Households | 2026 |
| Oakland Country Homes Ltd | Professional & scientific | 2010 |
| Oakleaf Financial Solutions Ltd | Financial services | 2025 |
| Oakley Coachbuilders Limited | Manufacturing | 2014 |
| Oakley Equestrian Clothing Ltd | Extraterritorial | 2011 |
| Oakley Horse Boxes Limited | Extraterritorial | 1978 |
| Oakley Renovations Ltd | Construction | 2019 |
| Oakwoods Group Limited | Wholesale & retail | 2007 |
| Ocean Delight Ltd | Hospitality | 2025 |
| Ochieng Pharm Ltd | Professional & scientific | 2025 |
| Octagon Telecom Limited | Information & communication | 2013 |
| Octavia Software Solutions Limited | Information & communication | 2002 |
| Oculus Property Leasing Ltd | Real estate | 2024 |
| Oculus Property Services Limited | Real estate | 2023 |
| Odjo Ltd | Information & communication | 2024 |
| Office Addins Ltd | Information & communication | 2024 |
| OFS Business Support Hub Ltd | Administrative & support | 2023 |
| Ofs.Team Ltd | Administrative & support | 2023 |
| OH Media Limited | Information & communication | 2025 |
| OH Yeah Finance Ltd | Financial services | 2014 |
| Ohlin Capital Limited | Extraterritorial | 2013 |
| OJA Properties Limited | Real estate | 2023 |
| OK Build Ltd | Construction | 2015 |
| Okuyucu Repair and Maintenance Ltd | Manufacturing | 2021 |
| OL Property Investments Limited | Real estate | 2026 |
| Olabow Limited | Financial services | 2018 |
| Old Kent Rovers Limited | Administrative & support | 2017 |
| Old Nursery Limited | Extraterritorial | 2021 |
| Old Stocks Oak Residents Limited | Households | 2007 |
| Olga and SON Ltd | Transport & logistics | 2021 |
| Oli's Skate Shop Limited | Construction | 2003 |
| Olivermax Limited | Financial services | 2013 |
| OLSTA99 Ltd | Construction | 2024 |