| Numiracle Limited | Professional & scientific | 2011 |
| Nunabio Limited | Professional & scientific | 2012 |
| Nuro Clothing Ltd | Wholesale & retail | 2026 |
| Nursery House Ltd | Education | 2013 |
| Nursery Properties (N.E.) Limited | Administrative & support | 2007 |
| Nurserytime Ltd | Health & social care | 2020 |
| Nursia Health Ltd | Health & social care | 2026 |
| Nurturalife Limited | Administrative & support | 2026 |
| Nurtureandnoodle Ltd | Hospitality | 2026 |
| Nurtured Birth & Beyond Ltd | Education | 2025 |
| NUSC2023 Ltd | Arts & recreation | 2023 |
| Nusu Trading Ltd | Wholesale & retail | 2019 |
| NUT Homeware UK Limited | Wholesale & retail | 2025 |
| Nutcombe Cambridge Holdings Limited | Financial services | 2024 |
| NUTRILICIOUS4YOU Ltd | Hospitality | 2023 |
| Nutrition North East Limited | Other services | 2023 |
| Nutro Limited | Wholesale & retail | 2025 |
| Nuvelen Technologies Ltd | Information & communication | 2025 |
| Nuvoke Property Solutions Ltd | Real estate | 2023 |
| Nuwsletter Ltd | Information & communication | 2025 |
| NV1 CP Limited | Financial services | 2012 |
| NV1 GP Limited | Financial services | 2012 |
| NV1 LP | | 2012 |
| NV2 CP Limited | Financial services | 2014 |
| NV2 LP | | 2014 |
| NV2 Nominee Limited | Financial services | 2014 |
| NV3 LP | | 2016 |
| NV3A LP | | 2022 |
| NV3B LP | | 2022 |
| NV3C LP | | 2023 |
| NV3D LP | | 2023 |
| NV3E LP | | 2024 |
| Nvision Studios Ltd | Professional & scientific | 2021 |
| NVM GP LLP | | 2014 |
| NVM III GP LLP | | 2017 |
| NVM Member 1 Limited | Financial services | 2017 |
| NVM Member 2 Limited | Financial services | 2017 |
| NVM Nominees Limited | Financial services | 2006 |
| NVM PE Limited | Financial services | 1987 |
| NVM Private Equity LLP | | 2014 |
| NVM Private Equity Vintage III L.P. | | 2017 |
| NW Heating and Plumbing Limited | Construction | 2021 |
| NW Investment Holdings Limited | Real estate | 2025 |
| NW Residential Limited | Real estate | 2005 |
| NWB Electrical Ltd | Construction | 2025 |
| Nwfa Limited | Arts & recreation | 2022 |
| Nwfpc Limited | Wholesale & retail | 2009 |
| Nwgh Holdings Limited | Financial services | 2021 |
| Nwgh Limited | Professional & scientific | 2020 |
| Nwsar Ltd | Other services | 2023 |
| Nxgen Solutions Ltd | Information & communication | 2025 |
| NYA Foods Ltd | Administrative & support | 2023 |
| Nyas Construction Ltd | Construction | 2020 |
| Nyatiti Nyadala CIC | Education | 2022 |
| Nyaz Investment Ltd | Real estate | 2025 |
| Nyle Homes Limited | Real estate | 2025 |
| Nyngan Estates Limited | Real estate | 2023 |
| Nysafawn Sporting Ltd | Agriculture & fishing | 2025 |
| Nytram Services Ltd | Real estate | 2024 |
| NZ Renewables UK Ltd | Professional & scientific | 2024 |
| O & E Properties Limited | Real estate | 2014 |
| O and J Westerhope Ltd | Hospitality | 2024 |
| O Communications Ltd | Professional & scientific | 2008 |
| O&L Holdings Limited | Real estate | 2020 |
| O&M Enterprises Ltd | Hospitality | 2026 |
| O'Brien Newcastle Ltd | Construction | 2023 |
| O'Neill Accountancy Limited | Professional & scientific | 2016 |
| O'Neill Richmonds Law Firm Limited | Professional & scientific | 2013 |
| O.A.E Properties Ltd | Real estate | 2024 |
| O.S. Energy (UK) Ltd | Transport & logistics | 2020 |
| O7 Events Ltd | Hospitality | 2024 |
| Oak and Stones Residential Ltd | Real estate | 2022 |
| Oak Ebooks Ltd | Information & communication | 2006 |
| Oak Engage Limited | Information & communication | 1999 |
| Oak Food Ltd | Hospitality | 2025 |
| Oak Northeast Ltd | Other services | 2020 |
| Oak Training ( UK ) Ltd | Education | 2016 |
| Oak Tree (NE) Ltd | Real estate | 2025 |
| Oak Window Film Company Limited | Construction | 2015 |
| Oak's Hospitality Ltd | Hospitality | 2024 |
| Oakbarm Properties Ltd | Real estate | 2025 |
| Oakbridge Food & Beverage Ltd | Hospitality | 2025 |
| Oakdever Limited | Real estate | 1989 |
| Oakfield Holiday Properties Ltd | Hospitality | 2021 |
| Oakfield Lodge Management Limited | Real estate | 2004 |
| Oakfield Tree & Hedge Services Limited | Administrative & support | 2021 |
| Oakglen Developments Limited | Construction | 2008 |
| Oakland Park (Masham) Management Company Limited | Real estate | 2022 |
| Oaklee Limited | Other services | 1996 |
| Oakleystone Northern Ltd | Manufacturing | 2008 |
| Oaks Property Developments Limited | Construction | 2012 |
| Oaks Properties Limited | Real estate | 1994 |
| Oaktree Cars and Vans Ltd | Wholesale & retail | 2018 |
| Oaktree Interiors Holdings Limited | Financial services | 2021 |
| Oakview Property Holdings Limited | Real estate | 2026 |
| Oakwood Estates Property Agents Holdings Ltd | Financial services | 2021 |
| Oakwood Hall Limited | Other services | 2020 |
| Oakyard (Midco) Top Limited | Financial services | 2022 |
| Oakyard Developments (Midco) Limited | Construction | 2022 |
| Oakyard Developments Limited | Financial services | 2021 |