| Npglo Limited | Health & social care | 2025 |
| Nple Limited | Health & social care | 2025 |
| Nplo Limited | Health & social care | 2025 |
| Npman Limited | Health & social care | 2025 |
| NPR Holdings Ltd | Real estate | 2026 |
| Npss Limited | Professional & scientific | 2017 |
| Npsu Limited | Health & social care | 2025 |
| NQ Homes Ltd | Financial services | 2023 |
| Nrdistributors Ltd | Wholesale & retail | 2026 |
| Nritya Alaap Centre for Odissi Ltd | Arts & recreation | 2025 |
| NRV Properties and Maintenance Limited | Real estate | 2021 |
| NS Bristol Ltd | Hospitality | 2026 |
| NS Chelsea Ltd | Hospitality | 2026 |
| NS Clapham Ltd | Hospitality | 2025 |
| NS Dental Sedate Ltd | Health & social care | 2025 |
| NS Leeds Ltd | Hospitality | 2026 |
| NS Newcastle Ltd | Hospitality | 2025 |
| NS Private Limited | Health & social care | 2022 |
| NS1 Ventures Ltd | Hospitality | 2025 |
| NSB Health Ltd. | Professional & scientific | 2016 |
| Nsbh Properties Ltd | Real estate | 2024 |
| Nscm Ltd | Wholesale & retail | 2022 |
| NSG Reserves Ltd | Real estate | 2025 |
| NSN Accountants Ltd | Professional & scientific | 2024 |
| NT Parekh Limited | Households | 2016 |
| Ntsb Limited | Real estate | 2023 |
| Nubestec Ltd | Information & communication | 2014 |
| Nueta Ventures Limited | Information & communication | 2012 |
| Nukare Holding Ltd | Financial services | 2020 |
| Numeric Technologies Ltd | Information & communication | 2010 |
| Nunoxx Limited | Wholesale & retail | 2025 |
| Nupa Property Services Limited | Real estate | 2019 |
| Nuroots Financial Limited | Financial services | 2025 |
| Nurul Properties Limited | Real estate | 2021 |
| NUT Walla Ltd | Wholesale & retail | 2024 |
| Nutrelis UK Limited | Wholesale & retail | 2019 |
| Nutrifresh Products Ltd | Wholesale & retail | 2022 |
| Nutrisha Wellness Limited | Wholesale & retail | 2026 |
| NV Bar and Hospitality Ltd | Hospitality | 2025 |
| Nvision Properties Ltd | Real estate | 2023 |
| NVK Commercial Ltd | Real estate | 2025 |
| NVK Investments Limited | Real estate | 2013 |
| NVM Group Services Ltd | Construction | 2025 |
| NVN Limited | Transport & logistics | 2023 |
| Nvoid Ltd | Wholesale & retail | 2021 |
| NVT Fire and Security Ltd | Construction | 2019 |
| Nvtr Limited | Hospitality | 2022 |
| NW London Commercial Limited | Real estate | 2023 |
| Nxgen Leads Ltd | Professional & scientific | 2025 |
| NYK OAS Ltd | Construction | 2025 |
| O & M Business International Group PLC | Professional & scientific | 2010 |
| O'Hara Bros. Construction Limited | Water & waste | 2010 |
| O.C.S Construction Ltd | Construction | 2002 |
| Oak International Brazil Limited | Real estate | 2016 |
| Oak International Finance Limited | Financial services | 1996 |
| Oakdale Plaza Freehold Limited | Households | 2004 |
| Oakedale Development Ltd | Real estate | 2018 |
| Oakfield Court (Welwyn) Management Company Limited | Real estate | 2023 |
| Oakfield Property Services Ltd | Real estate | 2024 |
| Oakfields Renewables Ltd | Wholesale & retail | 2016 |
| Oakhill Solutions Limited | Construction | 2015 |
| Oakington Four Limited | Real estate | 2024 |
| Oakington One Ltd | Real estate | 2024 |
| Oakington Property Management Limited | Real estate | 2024 |
| Oakington Three Limited | Real estate | 2024 |
| Oakington Two Limited | Real estate | 2024 |
| Oakland Place Limited | Real estate | 2021 |
| Oakrith Capital Limited | Real estate | 2025 |
| Oakwood Financial Planning Ltd | Financial services | 2023 |
| Oasis Stays Ltd | Hospitality | 2026 |
| Oatility Foods Limited | Manufacturing | 2018 |
| Obesum Ltd | Information & communication | 2025 |
| Objective UA Limited | Administrative & support | 2022 |
| Oblue Limited | Transport & logistics | 2012 |
| Oboya UK Co Ltd | Manufacturing | 2023 |
| OBR Technology Ltd | Information & communication | 2022 |
| Obsessed Music Limited | Arts & recreation | 2019 |
| Obsidian Associates Ltd | Administrative & support | 2016 |
| Obsidian Titan Studios Ltd | Information & communication | 2025 |
| Occasionall Ltd | Other services | 2025 |
| Ocean Drive Hotels Ltd | Hospitality | 2019 |
| Ocean Mount Ltd | Wholesale & retail | 2025 |
| Oceanlink Construct Ltd | Construction | 2018 |
| Octagonal Properties Limited | Real estate | 2019 |
| Octavian Communications Limited | Information & communication | 2020 |
| Octo E-Trade Ltd | Wholesale & retail | 2021 |
| Octopus ALL Trades Ltd | Construction | 2025 |
| Octti Ltd | Information & communication | 2024 |
| OD Camden Hotel Ltd | Real estate | 2019 |
| ODD Jewel International Ltd | Wholesale & retail | 2025 |
| Oddahappulam OUR Lady of Immaculate Conception Committee (UK) Ltd | Health & social care | 2013 |
| Odds and Ends Limited | Wholesale & retail | 2019 |
| Odhavji Investments Ltd | Real estate | 2017 |
| Oditable Limited | Information & communication | 2025 |
| Odyssey Build Projects Ltd | Manufacturing | 2025 |
| Off-Clock Automotive Ltd | Wholesale & retail | 2024 |
| Offbeatsneaks Ltd | Wholesale & retail | 2022 |
| Offbeatstore Ltd | Wholesale & retail | 2024 |
| Offbridge Properties Ltd | Real estate | 2023 |
| Offland Auto Services Ltd | Wholesale & retail | 2020 |