| Nufarul Ltd | Transport & logistics | 2025 |
| Nugo Financial Services Ltd | Information & communication | 2025 |
| NUH UK Weekend Islamic School CIC | Health & social care | 2026 |
| Nummus Limited | Real estate | 2025 |
| Numon TEC Ltd | Information & communication | 2022 |
| Nunodaa Ltd | Information & communication | 2025 |
| NUR Community Services C.I.C. | Professional & scientific | 2024 |
| Nurani Ltd | Wholesale & retail | 2023 |
| Nuraya Holdings Limited | Real estate | 2024 |
| Nurture Nest Care Ltd | Public administration | 2024 |
| Nurture Path Limited | Health & social care | 2026 |
| Nush Enterprises Ltd | Health & social care | 2015 |
| Nutribu Ltd | Wholesale & retail | 2020 |
| Nutripoint Slough Ltd | Wholesale & retail | 2017 |
| Nutriself Ltd | Wholesale & retail | 2025 |
| Nutritastic Limited | Manufacturing | 2019 |
| Nutrition for Body Mind and Soul Ltd | Health & social care | 2023 |
| Nutshelllambda Ltd | Information & communication | 2018 |
| Nuvio Stays Ltd | Real estate | 2025 |
| Nuvonic Limited | Manufacturing | 1980 |
| Nuvvi Ltd | Wholesale & retail | 2025 |
| NV Clinics Limited | Other services | 2023 |
| NV Constructions Ltd | Construction | 2019 |
| NVI Lounge Limited | Hospitality | 2025 |
| NW44 Limited | Transport & logistics | 2022 |
| NXA Limited | Information & communication | 2019 |
| Nxswrld Ltd | Professional & scientific | 2026 |
| Nxtgen Properties Limited | Real estate | 2026 |
| Nyasa Wellness Ltd | Education | 2026 |
| NYCOLLE06 Limited | Construction | 2023 |
| Nykps Ltd | Construction | 2019 |
| NYL Enterprise Limited | Wholesale & retail | 2025 |
| NYS Little Things Ltd | Wholesale & retail | 2024 |
| Nyss Trading Ltd | Wholesale & retail | 2019 |
| NZH Limited | Information & communication | 2015 |
| O & K Solutions Ltd | Construction | 2019 |
| O a & S Dynamic Associates Limited | Real estate | 2023 |
| O Consultants Limited | Wholesale & retail | 2016 |
| O P S Properties Limited | Real estate | 2018 |
| O&A Property Investment Ltd | Real estate | 2025 |
| O&P Bookkeeping Ltd | Professional & scientific | 2013 |
| O&Z Properties Ltd | Real estate | 2026 |
| O'Brien Haulage Ltd | Transport & logistics | 2016 |
| O'Connell Resourcing Ltd | Administrative & support | 2009 |
| O'Reilly Plastering Limited | Construction | 1998 |
| O'Sullivan U.K. Ltd | Manufacturing | 2020 |
| O.W.Francis Ltd | Construction | 2025 |
| O5 Neat & Clean Ltd | Administrative & support | 2025 |
| Oak & Key Management Ltd | Households | 2025 |
| Oak and Cedar Wood Ltd | Households | 2017 |
| Oak and Lane Ltd | Construction | 2026 |
| Oak Arrows Investments Ltd | Real estate | 2025 |
| Oak Holdings 3127 Limited | Real estate | 2021 |
| Oak Property Redevelopments Limited | Construction | 2021 |
| Oakbank CH Limited | Health & social care | 2020 |
| Oakfarm Homes Ltd | Real estate | 2023 |
| Oakhaven Care Services Ltd | Health & social care | 2025 |
| Oakley Fine Homes Limited | Construction | 2016 |
| Oakley Green, Fifield and District Community Association Limited | Other services | 2010 |
| Oakline Homes Ltd | Real estate | 2025 |
| Oakmargra Investment Group Ltd | Information & communication | 2019 |
| Oakmargra SPV Ltd | Real estate | 2025 |
| Oakmont Communications Ltd | Professional & scientific | 2025 |
| Oakmont Property Ltd | Real estate | 2026 |
| Oakswood Homes Limited | Construction | 2016 |
| Oakview Homes & Developments Ltd | Construction | 2021 |
| Oakwood Estates Property Agents Ltd | Real estate | 2008 |
| Oakwood Hill Construction Ltd | Construction | 2021 |
| Oakwood Hill Development Ltd | Construction | 2021 |
| Oasis Invest Ltd | Health & social care | 2025 |
| Oaten Homes Limited | Real estate | 2017 |
| Obey SHE Ltd | Professional & scientific | 2023 |
| Obhub Ltd | Wholesale & retail | 2026 |
| Obisoft Innovations UK Ltd | Manufacturing | 2021 |
| Oboh Emmanuel Eronmonse Limited | Extraterritorial | 2025 |
| Oboh Micah Enoseta Uwaiye Limited | Extraterritorial | 2025 |
| Oboh Sophina Irhagbon Limited | Extraterritorial | 2025 |
| Observatory News Slough Limited | Wholesale & retail | 2015 |
| Obsidian Rose Limited | Wholesale & retail | 2017 |
| OC Axiom Holdings Ltd | Financial services | 2024 |
| OC Painting Services Limited | Construction | 2022 |
| OC Recruitment Holdings Ltd | Financial services | 2024 |
| OC Solutions Ltd | Information & communication | 2022 |
| Ocarina Health Ltd | Health & social care | 2025 |
| Occasions Florist Oldham Ltd | Wholesale & retail | 2023 |
| Occasionsphotobooth Ltd | Professional & scientific | 2015 |
| Ocean Admedia Limited | Information & communication | 2009 |
| Ocean Blue Fish Bar Ltd | Hospitality | 2018 |
| Ocean Communicate Ltd | Wholesale & retail | 2025 |
| Oceangate Global Ltd | Wholesale & retail | 2024 |
| Oceanware Ltd | Professional & scientific | 2026 |
| Ocena Furniture Ltd | Other services | 2024 |
| Ockley Cars Limited | Transport & logistics | 2023 |
| Octal Securities Ltd | Wholesale & retail | 2024 |
| Octaven Medtech Ltd | Wholesale & retail | 2026 |
| Octavium Ltd | Real estate | 2025 |
| Octo Constructions Ltd | Construction | 2025 |
| Octo Plumbing & Heating Ltd | Construction | 2022 |
| Octoclean Limited | Administrative & support | 2020 |
| Octogan Consultancy Ltd | Professional & scientific | 2019 |